WO2014139861A1 - Complexes for the catalytic oligomerization of olefins - Google Patents

Abstract

The invention concerns transition metal complexes of the formula (I) which provide active and selective catalysts for the oligomerization of olefins, in particular ethylene, as well as methods for the oligomerization of olefins using the transition metal complexes.

Description

Complexes for the Catalytic Oiigomerization of Olefins

The invention relates to the oiigomerization of olefins, in particular the oiigomerization of ethylene, and to metal complexes which are able to provide catalyst compositions which efficiently and selectively catalyse the oiigomerization.

Technical Background

There is an increasing demand for linear a-olefins (LAO^'s), in particular for olefins having 4 to 10 carbon atoms (C₄-C₁₀ range). The high demand for LAO's is based on their broad spectrum of applications as additives or starting materials in other chemical processes. In addition, linear a-olefins are found as endproducts in various applications. For example, the light fractions 1 -butene, 1 -hexene and 1 -octene are used as comonomers in the rapidly growing polymer market, in particular for the production of LLDPE (Linear Low Density Polyethylene). The middle fractions, such as 1 -decene. 1 -dodecene and 1 -tetradecene are raw materials for synthetic oils, detergents and shampoos. Heavy fractions can be used as additives for lubricating oils, tensides, oil field chemicals, and as waxes.

A!pha-olefins can be prepared via Fischer-Tropsch-Synthesis. Here, either the Coal-to-Liquid- process (CtL-process) or the Gas-to-Liquid-process (GtL-process) can be used. In the CtL- process, the coal is first reacted at very high temperatures (above 1000°C) with water vapour and air or oxygen to form synthesis gas which, subsequent to the separation of nitrogen oxides and sulphur dioxide, is reacted via heterogeneous catalysis to form hydrocarbons including α-o!efins and water. In the GtL-process. natural gas is reacted via addition of oxygen and water vapour to form synthesis gas, and the latter is transformed into hydrocarbons in a Fischer-Tropsch-Synthesis. Both processes have the disadvantage that, besides the desired a-oiefins, a broad variety of products (paraffins and alcohols) is produced. This means that the pure α-olefins become only accessible after elaborate purification processes (e.g. DE 10022466 At). Other industrial-scale procedures for the preparation of a-olefins are the cracking of paraffins, the dehydration of paraffins and the dehydrogenisation of alcohols, or chain growth reactions including the oiigomerization of ethylene (W. Keim, A. Behr, G. Schmitt, Grundlagen der Industriellen Chemie - Technische Produkte und Prozesse, 1 . Auflage; Otto Salle Verlag GmbH und Co.: Frankfurt am Main, Germany, 1986; S. 126 - 150). Since ethylene represents an easily accessible raw material source, the first types of reactions play hardly any role for the industrial production today. In addition, the production of α-olefins via oiigomerization of ethylene provides exclusively olefins with an even number of C-atoms which have the highest value for commercial applications (cf. J. Skupinska, Chem. Rev. 1991. 91, 613-648; G. J. P. Britovsek, V. C. Gibson, D. F. Wass, Angew. Chem. Int. Ed. 1999, 38, 428-447; S. D. Ittel, L. K. Johnson, M. Brookhart, Chem. Rev. 2000, 100, 1 169-1204). Some of the most important industrially used production processes for LAO^'s which are based on the oiigomerization of ethylene are the following (A. Forestiere, H. Olivier-Bourbigou, L Saussine, Oil Gas Sci. Technot. 2009, 64, 649-667):

- the Shell Higher-Olefin-Process (SHOP; cf. W. Keim, Angew. Chem. Int. Ed. Engl. 1990, 29, 235-244; D. Vogt, Oiigomerization of Ethylen to Higher Linear a-Olefins, in Applied Homogeneous Catalysis with Organometallic Compounds: B. Cornils, W. A. Hermann: VCH: New York. 1996; Vol. 1 , S. 245-258: G. R. Lappin, J. D. Sauer. Alphaolefins Applications Handbook: Marcel Decker Inc.: Berkeley, CA, 1989) using a nickel complex;

- the a-Sablin-process {European Chemical News, 5-1 1 November 2001 , p. 27: P. M. Fritz, H. V. Boelt, Process Worldwide 2005, 8, 26-28; P. M. Fritz, H. V. Boelt, Linde Technology 2004, 2, 38-45) which uses a zirconia salt as a precatalyst;

- the Chevron-Phillips-Gulf-process and the INEOS-ethyl-process (D. Vogt, Oiigomerization of Ethylen to Higher Linear α-Olefins, in Applied Homogeneous Catalysis with Organometallic Compounds; B. Cornils, W. A. Hermann: VCH: New York. 1996; Vol. 1 , S. 245-258; G. R. Lappin. J. D. Sauer, Alphaolefins Applications Handbook; Marcel Decker Inc.: Berkeley, CA, 1989; Alpha Olefins (06/07-5), PERP Report, Nexant ChemSystems, 2008) which rely on the aluminum alkyi mediated oiigomerization of ethylene.

In addition to the above processes, which yield more or less broad distribution of a-olefins having different chain lengths, there are processes which selectively produce a single a-olefin in high purity. They include the Chevron-Phillips trimerisation process for the production of 1 - hexen (cf. Sami Matar, Lewis F. Hatch, Chemistry of Petrochemical Processes, Gulf Publishing Company, 2000, 2^nd Edition, S. 209ff), the Sasol tri- and tetramerisation process yielding 1 -hexene and 1 -octene (e.g. US 8,076,523 B2) and the Axens/Sabic Alphabutol- process yielding 1 -butene (A. Mortreux, F. Petit, Industrial applications of homogeneous catalysis. Kluwer, Dordrecht. 1988, S. 190).

Further approaches for complex catalyzed oligomerization reactions to form a-olefins are disclosed in EP 1 362 837 A1 . EP 2 070 593 A1 , US 2010/0286349 A1 or WO 2012/080588 A1 .

However, a need remains for metal complexes which provide highly active and thus efficient catalyst system which lead to the selective production of α-olefins at mild reaction conditions and with a high yield.

Summary of the Invention

The present invention provides complexes of the following formula (I), as well as catalyst systems using these complexes:

wherein

M is a metal selected from Zr and Hi;

X¹ and X² are independently selected from CI, Br, I, F, H, alkyl, -alkyl-O-alkyl, -aikyl-Q- aryl, alkoxy. aryloxy, aralkyl, -alkyl-SiR³R^bR^c and R¹R², wherein any alkyl group is optionally substituted by one or more substituents selected from OH, F, CI, Br. NH₂, NH(C1 -8 alkyl) and N(C1 -8 alkyl)₂, and any aryl group is optionally substituted by one or more substituents selected from C1 -8 alkyl, phenyl, C1 -8 alkoxy, OH, F, CI, Br, NH₂, NH(C1 -8 alkyl) and N(C1 -8 alkyl)₂;

L is selected from CZ³, N, and PR³R⁴;

Z¹ and Z² are independently selected from alkyl, cycloalkyl, heterocycloalkyl, alkenyl, aryl, heteroaryl, aralkyl, -alkyl-O-alkyl, -alkyl-O-aryl, wherein any alkyl group, alone or as part of another group, and any alkenyl group is optionally substituted by one or more substituents selected from F, CI, Br and N(C1 -8 alkyl)₂ and any aryl group, alone or as part of another group, and any heteroaryl group is optionally substituted by one or more substituents selected from C1 -8 alkyl, phenyl. C1-8 alkoxy, F, CI, Br. and N(C1 -8 alkyl)₂;

Z³ is selected from H, alkyl, cycloalkyl, heterocycloalkyl, alkenyl, alkoxy, aryl, aryloxy, heteroaryl. aralkyl, -alkyl-O-alkyl, -alkyl-O-aryl, F, CI. Br, NR R², and PR³R⁴, wherein any alkyl group, alone or as part of another group, and any alkenyl group is optionally substituted by one or more substituents selected from F, CI. Br, and N(C1-8 alkyl)₂ and wherein any aryl group, alone or as part of another group, and any heteroaryl group is optionally substituted by one or more substituents selected from C1-8 alkyl, phenyl. C1 -8 alkoxy. F, CI, Br. NH₂ and N(C1 -8 alkyl)₂;

or any suitable groups Z¹ and Z³ or Z² and Z³ as defined above may be linked to form an optionally substituted five- to seven-membered heterocyclic ring incorporating the nitrogen atom to which Z¹ is attached or the nitrogen atom to which Z² is attached;

J is selected from a ligand of the formula (II) or (III):

wherein

Q¹ to 0° are independently selected from alkyl, cycloalkyl. heterocycloalkyl, alkenyl, alkoxy, aryl, aryloxy, heteroaryl, aralkyl, -alkyl-O-alkyl. -alkyl-O-aryt and NR^DR⁶, wherein any alkyl group, alone or as part of another group, and any alkenyl group is optionally substituted by one or more substituents selected from F. CI, Br and N(C1 -8 alkyl)₂ and wherein any aryl group , alone or as part of another group, is optionally substituted by one or more substituents selected from C1 -8 alkyl, phenyl, C1 -8 alkoxy, F, CI, Br and N(C1 -8 a!kyl)₂;

or any suitable groups Q¹ and Q² as defined above may be linked to form a five- to seven-membered, carbocyclic or heterocyclic, saturated or unsaturated ring together with the carbon atom to which they are attached, or any suitable groups Q⁵ and Q⁴ as defined above or Q⁴ and Q⁵ as defined above may be linked to form a five- to seven-membered, heterocyclic, saturated or unsaturated ring together with the P-atom to which they are attached; R^a, R° and R^c are independently selected from alkyl and aryl; and

R¹, R², R³, R⁴, R⁵ and R⁶ are independently selected from H, alkyl, cycloalkyl, alkenyl, aryl, and aralkyl, wherein any alkyl group, alone or as part of aralkyl, is optionally substituted by one or more substituents selected from F, CI, Br and N(C1 -8 alkyl)₂ and wherein any aryl group, alone or as part of aralkyl, is optionally substituted by one or more substituents selected from C1 -8 alkyl, phenyl, C1 -8 alkoxy, F, CI, Br and N(C1 -8 alkyl)₂;

or any suitable groups R¹ and R² as defined above, R³ and R⁴ as defined above or R⁵ and R⁶ as defined above may be linked to form an optionally substituted five- or six- membered heterocyclic ring including the N or P atom to which they are attached; or, where Q^* and Q². Q³ and Q⁴ or Q⁴ and Q⁵ are NR⁵R⁶, two groups R⁵ or two groups R⁶ as defined above may be linked to form an optionally substituted saturated or unsaturated heterocycle including the two N atoms of the groups NR⁵R⁶;

or one of Q¹ to Q⁵ as defined above may be linked with one of Z¹ or Z² as defined above to form a metallacycle including .

In addition, the invention relates to processes for the oiigomerization of olefins, in particular of ethylene, which are catalyzed by the complexes or catalyst systems in accordance with the invention.

The complexes in accordance with the invention are able to provide highly active catalyst systems for the selective synthesis of a-olefins, in particular short chain α-o!efins in the C₄-C₁₀ range. The complexes can be conveniently prepared form starting compounds described in the literature, and they catalyze the oiigomerization of olefins under conditions which are significantly milder in terms of their high selectivity at lower temperatures and at a lower pressure compared to known industrial processes. Moreover, the amounts of catalysts which are required in order to achieve a satisfactory yield are very low, such that large amounts of products can be prepared using small amounts of catalysts. In comparison with systems previously described in the literature and used in industry, the catalyst system in accordance with the invention has the additional advantage that a narrow product distribution of the a- olefins results.

Detailed Description

A "catalyst composition" as referred to herein refers to a composition comprising the complex of the invention (i.e. the complex of formula (I) or any preferred embodiment thereof) as such or in an activated form obtainable by reacting the complex with an activator, which system can be contacted with the reactants to be subjected to the catalyzed reaction. Typical examples are a solution or a dispersion of the complex or the activated complex, or a carrier on which the complex or the activated complex is immobilized, e.g. via adsorption.

The complex of the invention (i.e. the complex of formula (I) or any preferred embodiment thereof) can also be referred to as a "precatalyst" herein. In accordance with the practice in the art, the term "precatalyst" refers to a complex in a form which is converted into the catalytically active species, e.g. via abstraction of a ligand, during the course of the catalyzed reaction. The activation can be assisted by an activator or a co-catalyst.

Oligomerization, in accordance with the understanding in polymer chemistry, relates to a process wherein monomers are covaientiy linked to each other to form a product (oligomer) containing a limited number of subunits derived from these monomers. Generally, the total number of subunits in an oligomer does not exceed 100. In the oligomers provided by the complexes and methods in accordance with the invention, a number of monomer subunits of 2 to 20 is preferred, a number of 2 to 15 is more preferred, and a number of 2 to 12 is further preferred and a number of 2 to 10 is particularly preferred. It will be understood that oligomer mixtures obtained in an oligomerization reaction as carried out in the context of the invention show a distribution with respect to their chain lengths. Generally, the peak (or peaks) of such a product distribution indicating the relative weight ratio of oligomers in the mixture versus the number of subunits contained in the oligomer (e.g. determined via gas chromatography) lies in the range of 2 to 5, in particular 2 to 3.

As used herein, "alkyi" represents a straight or branched chain saturated hydrocarbon residue which does not comprise any carbon-to-carbon double bonds or carbon-to-carbon triple bonds. Unless otherwise defined in a specific context, alkyi groups with 1 to 8 carbon atoms are generally preferred in the context of the invention. As exemplary groups, methyl, ethyl, propyl and butyl are mentioned.

As used herein, "alkenyl" represents a straight or branched chain unsaturated hydrocarbon residue comprising one or more than one (such as two or three) carbon-to-carbon double bond(s) which does not comprise any carbon-to-carbon triple bonds. Unless otherwise defined in a specific context, alkenyl groups with 1 to 8 carbon atoms and one or two double bonds are generally preferred in the context of the invention. As used herein, "aryl" represents an aromatic hydrocarbon ring, in particular a 6 to 10 membered ring (unless a different number of ring members is indicated in a specific context), including bridged ring or fused ring systems containing at least one aromatic ring. "Aryl" may, for example, refer to phenyl or naphthyl. Preferred as aryl groups are monocyclic groups with 6 or fused bicyclic groups with 9 or 10 ring members. Thus, generally preferred embodiments of "aryl" are phenyl or naphthyl, and particularly preferred is phenyl.

As used herein, "aralkyl" represents an alkyl group as defined above, wherein one or more, preferably one hydrogen atom is replaced by an aryl group, preferably a phenyl group. A particularly preferred aralkyl group is benzyl.

The term "-alkyl-O-alkyi" refers to an alkyl group as defined above, wherein one hydrogen atom is replaced by an alkoxy group. Likewise, the term "-alkyl-O-ary refers to an alkyl group as defined above, wherein one hydrogen atom is replaced by an aryloxy group.

As used herein, a "heterocycie" is a ring comprising one or more (such as, e.g., one, two. or three) ring heteroatoms which may be selected from O, S, and N, including bridged ring or fused ring systems. A heterocycie may be saturated or unsaturated, such that the term encompasses heteroalkyl rings as well as heteroraryl rings. Preferred are 5 - 14 membered rings, and particular preference is given to monocyclic groups with 5 or 6 members and fused bicyclic groups with 8 to 10 ring members.

As used herein, "heteroaryl" represents an aromatic ring, preferably a 5-14 membered ring (unless a different number of ring members is indicated in a specific context), including bridged ring or fused ring systems containing at least one aromatic ring, comprising one or more (such as, e.g. , one, two, or three) ring heteroatoms independently selected from O, S, and N. Particularly preferred as heteroaryl groups are monocyclic groups with 5 or 6 members and fused bicyclic groups with 8 to 10 ring members. "Heteroaryl^" may. for example, refer to thienyl (thiophenyl), benzo[b]thienyl. naphtho[2,3-b]thienyl, thianthrenyl, fury I (furanyl), isobenzofuranyl. chromenyl, xanthenyl, phenoxathlinyl. pyrrolyl (including, without limitation, 2H-pyrrolyl), imidazo!yl, pyrazolyl, pyridyl (pyridinyl; including, without limitation, 2-pyridyl, 3- pyridyl, and 4-pyridyl), pyrazinyl, pyrimidinyl, pyridazinyl, indolizinyl, isoindolyl, indolyl (including, without limitation, 3H-indolyl), indazolyl, purinyl, isoquinolyl, quinolyl, phthalaziny!, naphthyridinyl, quinoxalinyl, cinnolinyl, pteridinyl, carbazolyl, beta-carbolinyl, phenanthridinyi, acridinyl, phenanthrolinyl (including, without limitation, [1 ,10]phenanthrolinyl, [1 ,7]phenanthro- linyl, and [4,7]phenanihrolinyl), phenazinyl, isothiazolyl, phenothiazinyl, oxazolyl, isoxazolyl, furazanyl, phenoxazinyl, pyrazolo[1 ,5-a]pyrimidinyl (including, without limitation, pyrazolo[1.5- a]pyrimidin-3-yl). 1 ,2-benzoisoxazol-3-yl, or benzimidazolyl.

As used herein, "cycloalkyl" represents a saturated hydrocarbon ring, preferably a 3-1 1 membered ring (unless a different number of ring members is indicated in a specific context), including bridged ring, spiro ring or fused ring systems. "Cycloalkyl" may, for example, refer to cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, or cycloheptyl. Preferred as cycloalkyl groups are monocyclic groups with 5 or 6 ring members or fused bicyclic groups with 9 or 10 ring members.

As used herein, ^"heterocycloalkyi" represents a saturated ring, preferably a 3-1 1 membered ring (unless a different number of ring members is indicated in a specific context), including bridged ring, spiro ring or fused ring systems, containing one or more (such as, e.g.. one, two, or three) ring heteroatoms independently selected from O, S, and N. Particularly preferred as heterocycloalkyi groups are monocyclic groups with 5 or 6 members and fused bicyclic groups with 8 to 10 ring members. "Heterocycloalkyi" may, for example, refer to oxetanyl, tetrahydrofuranyl, piperidinyl, piperazinyl, aziridiny!, azetidinyl, pyrrolidinyl, imidazolidinyl, morpholinyl, pyrazo!idinyl, tetrahydrothienyl, octahydroquinolinyl, octahydroisoquinolinyl. oxazolidinyi, isoxazolidinyl, azepanyl, diazepanyl. oxazepanyl or 2-oxa-5-aza- bicycio[2.2.1 ]hept-5-yl.

As far as the compounds and complexes used herein allow two suitable groups to be linked to form a ring, it will be understood by the skilled person that the concerned groups should, in combination, be sufficiently long such that the resulting ring system can be stable. In addition, it will be understood that two groups can be linked if they contain atoms between which a bond (including single or double bonds) can be formed. As example, a link can be formed between two carbon atoms in different groups via replacement of one or two hydrogen atom in each of the groups by a bond or a double bond between the groups.

As defined above, the present invention provides in accordance with a first aspect complexes of the following formula (I):

wherein

M is a metai selected from Zr and Hf;

X¹ and X² are independently selected from CI, Br, I, F, H, alkyl, -alkyl-O-alkyi, -alkyl-O- aryl, alkoxy, aryioxy. aralkyi, -alkyl-SiR^aR^bR^c, and NR¹R², wherein any alkyl group, alone or as part of another group such as -alkyl-O-alkyl, alkoxy or aralkyi, is optionally substituted by one or more substituents selected from OH. F, CI, Br, NH₂, NH(C1 -8 alkyl) and N(C1-8 alkyl)₂, and any aryi group, aione or as part of another group such as -alkyl-O-aryl, aralkyi or aryioxy, is optionally substituted by one or more substituents selected from C1 -8 alkyl, phenyl, C1 -8 alkoxy, OH, F, CI. Br. NH₂, NH(C1 -8 alkyl) and N(C1 -8 alkyl)₂;

L is selected from CZ³, N, and PR³R⁴;

Z¹ and Z² are independently selected from alkyl, cycloalkyl, heterocycloalkyi, alkenyl, aryi, heteroaryl, aralkyi, -alkyl-O-alkyl, -alkyl-O-aryl, wherein any alkyl group, alone or as part of another group such as -alkyl-O-alkyl or aralkyi. and any alkenyl group, is optionally substituted by one or more substituents selected from F, CI, Br and N(C1 -8 alkyl)₂ and any aryi group, alone or as part of another group, such as -alkyl-O-aryl or aralkyi, and any heteroaryi group, is optionally substituted by one or more substituents selected from C1 -8 alkyl, phenyl, C1 -8 alkoxy, F. CI, Br and N(C1 -8 alkyl)₂;

Z³ is selected from alkyl, cycloalkyl, heterocycloalkyi, alkenyl, alkoxy, aryi, aryioxy, heteroaryi, aralkyi, -alkyl-O-alkyl, -alkyl-O-aryl, F, CI, Br, NR¹R², and PR³R⁴, wherein any alkyl group, alone or as pari of another group such as -alkyl-O-alkyl, alkoxy or aralkyi, and any alkenyl group, is optionally substituted by one or more substituents selected from OH, F, CI, Br and N(C1 -8 alkyl)₂ and wherein any aryi group, alone or as part of another group such as - alkyl-O-aryl, aralkyi or aryioxy, and any heteroaryl group, is optionally substituted by one or more substituents selected from C1 -8 alkyl, phenyl, C1 -8 alkoxy, F, CI, Br and N(C1 -8 alkyl)₂; or any suitable groups Z¹ and Z³ or Z² and Z³ as defined above may be linked to form an optionally substituted five- to seven-membered heterocyclic ring incorporating the nitrogen atom to which Z¹ is attached or the nitrogen atom to which Z² is attached;

J is selected from a ligand of the formula (II) or (III)

wherein

Q¹ to Q⁵ are independently selected from alkyl, cycloalkyl, heterocycloalkyl. alkenyl, alkoxy, aryl, aryloxy, heteroaryl, aralkyl. -alkyl-O-alkyl, -alkyl-O-aryl and NR⁵R⁶, wherein any alkyl group, alone or as part of another group, and any alkenyl group is optionally substituted by one or more substituents selected from F, CI, Br and N(C1 -8 alkyl)₂ and wherein any aryl group , alone or as part of another group, is optionally substituted by one or more substituents selected from C1 -8 alkyl, phenyl, C1 -8 alkoxy, F, CI, Br and N(C1 -8 alkyl)₂;

or any suitable groups Q¹ and Q² as defined above may be linked to form a five- to seven-membered, carbocyclic or heterocyclic, saturated or unsaturated ring together with the carbon atom to which they are attached, or any suitable groups Q³ and Q⁴ as defined above or Q⁴ and Q⁵ as defined above may be linked to form a five- to seven-membered, heterocyclic, saturated or unsaturated ring together with the P-atom to which they are attached;

R^a, R^u and R° are independently selected from alkyl and aryl; and

R¹, R², R³, R⁴, R⁵ and R⁶ are independently selected from H, alkyl, cycloalkyl, alkenyl, aryl, and aralkyl, wherein any alkyl group, alone or as part of aralkyl, is optionally substituted by one or more substituents selected from F. CI, Br and N(Cl -8 alkyl)₂ and wherein any aryl group, alone or as part of aralkyl, is optionally substituted by one or more substituents selected from C1 -8 alkyl, phenyl, C1 -8 alkoxy, F, CI, Br, NH₂, NH(C1 -8 alkyl) and N(C1 -8 alky!)₂; or any suitable groups R¹ and R² as defined above. R³ and R⁴ as defined above or R⁵ and R⁶ as defined above may be linked to form an optionally substituted five- or six- membered heterocyclic ring including the N or P atom to which they are attached; or, where Q¹ and Q², Q³ and Q⁴ or Q⁴ and Q⁵ are NR⁵R⁶, two groups R⁵ or two groups R⁶ as defined above may be linked to form an optionally substituted, saturated or unsaturated heterocycle including the two N atoms of the groups NR⁵R⁶; or one of Q¹ to Q⁵ as defined above may be linked with one of Z or Z² as defined above to form a metallacycle including M.

As regards the ligand formed by Z\ N, L, N and Z², it will be understood that the delocaiization of the electrons in the ligand indicated by the dashed bonds in the formula (I)

is influenced by the electron structure of the groups Z¹, Z² and L. Thus, a strongly delocaiized system will be formed if L is a group CZ³ and the concerned ligand is symmetrical with respect to L, In this case, the bonds formed by the nitrogen atoms to the metal center are equivalent. However, the structure of the complexes of formula (I) embraces constellations wherein the delocaiization would be less pronounced, such that one of the N atoms can be considered as an anionic atom which binds with the metal, the other one as a neutral atom coordinating with an electron lone pair, as illustrated in the following formulae (Γ) and (I").

As noted above, the electron structure of the nitrogen metal bonds will be ultimately determined by the nature of associated groups Z\ L, and Z², and the actual structure will frequently be an intermediate between the idealized resonance structures (I) and (Γ) or (I"). Thus, the indication of a resonance structure such as (I), ([') or (Γ) for any complexes described herein is not to be seen as limiting the concerned compounds to the illustrated equivalent or non-equivalent types of nitrogen-metal bonds in accordance with the common practice in the art.

In the ligand containing Z , L and Z², the following are preferred meanings of these variables. L is preferably CZ³.

Z¹ and Z² are preferably selected from alkyl, cycloalkyl, heterocycloalkyl, aryl. heteroaryl, aralkyi, -alkyl-O-alkyl, and -alkyl-O-aryl, wherein any alkyl group, alone or as part of another group such as aralkyi, -alkyl-O-alkyl, and -alkyl-O-aryl, is optionally substituted by one or more substituents selected from F, CI, Br and N(C1 -8 alkyl)₂ and any aryl group, alone or as part of another group, such as aralkyi and -alkyl-O-aryl, is optionally substituted by one or more substituents selected from C1 -8 alkyl, phenyl, C1 -8 alkoxy, F, CI, Br and N(C1 -8 alkyl)₂. It is particularly preferred that Z¹ and Z² are selected from alkyl, cycloalkyl, aryl, and aralkyi, wherein any alkyl group, alone or as part of aralkyi, is optionally substituted by one or more substituents selected from F, CI, Br and N(C1 -8 alkyl)₂ and any aryl group, alone or as part of aralkyi, is optionally substituted by one or more substituents selected from C1 -8 alkyl, phenyl, C1 -8 alkoxy. F, CI. Br and N(C1 -8 alkyl)₂. Preferably, the alkyl group is not substituted and the aryl group is not substituted or substituted by one or more CI -8 alkyl groups.

Z³ is preferably selected from H, alkyl, cycloalkyl, aryl, aralkyi. and NR 'R², wherein any alkyl group, alone or as part of aralkyi, is optionally substituted by one or more substituents selected from F, CI, Br and N(C1 -8 alkyl)₂ and wherein any aryl group, alone or as part of aralkyi, is optionally substituted by one or more substituents selected from C1 -8 alkyl, phenyl, C1 -8 alkoxy. F. CI, Br and N(C1 -8 alkyl)₂. Preferably, the alkyl and the aryl group is not substituted

According to another preferred embodiment, Z¹ and Z³ or Z² and Z³ are taken together to form a pyridine ring including the nitrogen atom to which Z¹ or Z², respectively, is attached, which pyridine ring is optionally substituted by one or more substituents selected from C1 -8 alkyl, phenyl, C1 -8 alkoxy, F, CI, Br and N(C1 -8 alkyl)₂. Preferably, it is unsubstituted. The group Z or Z² which is not involved in the formation of the pyridine ring is defined in accordance with the preferred options listed above. R¹ and R² are preferably independently selected from H, alkyl. cycloalkyl, aryl. and aralkyi, wherein any aikyi group, alone or as part of aralkyi, is optionally substituted by one or more substituents selected from F. CI, Br and N(C1 -8 alkyl)₂ and wherein any aryl group, alone or as part of aralkyi. is optionally substituted by one or more substituents selected from C1 -8 alkyl, phenyl. C1 -8 a!koxy, F, CI, Br and N(C1 -8 alkyl)₂; or R¹ and R² as defined above may be linked to form an optionally substituted five or six-membered heterocyclic ring including the N atom to which they are attached. More preferably R¹ and R² are independently selected from H, alkyl, aryl, and aralkyi. and are in particular independently selected from H and C1 -8 alkyl.

In a particularly preferred embodiment, the ligand containing Z , L and Z² is selected from one of the following formulae (IVa) to (IVc):

In these formulae, the variables have the following general and preferred meanings.

R⁷, R⁸, and R⁹ are independently selected from alkyl, cycloalkyl, aryl, and aralkyi, wherein any aryl group, alone or as part of aralkyi, is optionally substituted by one or more substituents selected from CI -8 alkyl, phenyl, C1 -8 alkoxy. F. CI, Br and N(C -8 alkyl)₂. Preferably, the aryl group is not substituted or substituted by one or more CI -8 alkyl groups.

It is preferred that R^' . R⁸, and R⁸ are independently selected from aryl and aralkyi, wherein any aryl group, alone or as part of aralkyi, is optionally substituted in the ortho- and/or para- position by one or more C1 -8 alkyl groups. It is particularly preferred that R⁷, R^s, and R⁹ are independently phenyl, optionally substituted in the ortho- and/or para-position by one or more C1 -8 alkyl groups.

R¹⁰ is selected from H, alkyl. cycloalkyl, aryl, and aralkyl, wherein any aryl group, alone or as part of aralkyl, is optionally substituted by one or more substituents selected from C1 -8 alkyl, phenyl, C1 -8 alkoxy F, CI, Br and N(C1 -8 alkyl)₂. Preferably, the aryl group is not substituted or substituted by one or more C1 -8 alkyl groups.

It is preferred that R¹⁰ is selected from aryl and aralkyl, wherein any aryi group, alone or as part of aralkyl. is optionally substituted in the ortho- and/or para-position by one or more C1 -8 alkyl groups. It is particularly preferred that R¹⁰ is phenyl, optionally substituted in the ortho- and/or para-position by one or more C1 -8 alkyl groups.

R¹¹ and R ² are independently selected from H, alkyl, cycloalkyl, aryl, and aralkyl, wherein any alkyl group, alone or as part of aralkyl, is optionally substituted by one or more substituents selected from F, C!, Br and N(C1-8 alkyl)₂ and wherein any aryl group, alone or as part of aralkyl, is optionally substituted by one or more substituents selected from C1 -8 alkyl. phenyl, C1 -8 alkoxy, F, CI, Br and N(C1 -8 alkyl)₂; or R¹¹ and R¹² as defined above may be linked to form an optionally substituted five or six-membered heterocyclic ring including the N atom to which they are attached. Preferably R¹¹ and R¹² are independently selected from H, alkyl, aryl, and aralkyl, and are in particular independently selected from H and C1 -8 alkyl.

Among the ligands of formulae (IVa) to (IVc), particular preference is given in the context of the invention to ligands of formula (IVa).

Among the ligands of formulae (II) and (III) as J, preference is given to the ones of formula (II).

For a ligand J of formula (II), the compound of formula (I) has the following structure (la)

wherein the variables are defined as above, including preferred embodiments.

In the ligand containing Q¹ and Q², the following are preferred meanings for these variables.

Q¹ and Q² are preferably independently selected from alkyl, aryl. aralkyl, and NR⁵R⁶, wherein any alkyl group, alone or as part of aralkyl, is optionally substituted by one or more substituents selected from F, CI, Br and N(C1 -8 alkyl)₂ and wherein any aryl group, alone or as part of another group such as -alkyl-O-aryl, aralkyl or aryloxy, is optionally substituted by one or more substituents selected from C1 -8 alkyl, phenyl. C1 -8 alkoxy. F, CI, Br and N(C -8 alkyl)₂.

R⁵ and R⁶ are preferably independently selected from alky!, and aralkyl, wherein any alkyl group, alone or as part of aralkyl, is optionally substituted by one or more substituents selected from F, CI, Br and N(C1-8 alky!)₂ and wherein any aryl group, aione or as part of aralkyl, is optionally substituted by one or more substituents selected from C1 -8 alkyl, phenyl, C1 -8 alkoxy, F, CI, Br and N(C1 -8 alkyl)₂.

In accordance with a further preferred embodiment, Q¹ and Q² are both NR⁵R^6a, wherein the groups R⁵ are independently selected from the preferred options listed above, and the two groups R^6a are taken together to form a 5- or 6- membered, preferably 5 membered, saturated or unsaturated heterocycle containing the two N atoms of the NR⁵R^6a groups as heteroatoms. In addition to the groups R⁵, the heterocycle may carry one or more further substituents selected from C1-8 alkyl, phenyl, C1 -8 alkoxy, F, CI, Br and N(C1 -8 a!kyl)₂. Preferably, these further substituents are absent.

In a particularly preferred embodiment, the ligand of formula (II) is selected from one of the following formulae (lla) to (lie):

The variables in these formulae are defined as follows:

R¹³ and R¹⁴ are independently selected from H, alkyl, cycloalkyl, aryl, and aralkyl, wherein any alkyl group, alone or as part of aralkyl, is optionally substituted by one or more substituents selected from F, CI, Br and N(C1 -8 alkyl)₂ and wherein any aryl group, alone or as part of aralkyl, is optionally substituted by one or more substituents seiected from C1 -8 alkyl, phenyl, C1 -8 alkoxy. F, CI, Br and N(C1 -8 alkyl)₂. Preferably, the aryl group is not substituted or substituted by one or more C1 -8 alkyl groups.

It is preferred that R¹³ and R¹⁴ are independently selected from aryl and aralkyl, wherein any aryl group, alone or as part of aralkyl, is optionally substituted in the ortho- and/or para- position by one or more C1 -8 alkyl groups. It is particularly preferred that R¹³ and R are independently phenyl, optionally substituted in the ortho- and/or para-position by one or more C1 -8 alkyl groups.

R¹⁵ and R¹⁶ are independently selected from alkyl, cycloalkyl, aryl, and aralkyl, wherein any aryl group, alone or as part of aralkyl, is optionally substituted by one or more substituents selected from C1 -8 alkyl, phenyl, C1 -8 alkoxy. F, CI, Br and N(C1 -8 alkyl)₂. Preferably, the aryl group is not substituted or substituted by one or more C1 -8 alkyl groups.

It is preferred that R¹⁵ and R ⁶ are independently selected from aryl and aralkyl, wherein any aryl group, alone or as part of aralkyl, is optionally substituted in the ortho- and/or para- position by one or more C1 -8 alkyl groups. It is particularly preferred that R ⁵ and R¹⁶ are independently phenyl, optionally substituted in the ortho- and/or

para-position by one or more C1-8 alkyl groups.

R¹⁷, R^{1 B}, R¹⁹ and R²⁰ are independently selected from H, alkyl, cycloalkyl, aryl, and aralkyl, wherein any alkyl group, alone or as part of aralkyl, is optionally substituted by one or more substituents selected from F, CI, Br and N(C1 -8 alkyl)₂ and wherein any aryl group, alone or as part of aralkyl, is optionally substituted by one or more substituents selected from C1 -8 alkyl. phenyl, C1 -8 alkoxy, F, CI, Br and N(C1 -8 alkyl)₂; or R¹⁷ and R¹⁸ or R¹⁹ and R²⁰ as defined above may be linked to form an optionally substituted five or six-membered heterocyclic ring including the N atom to which they are attached. Preferably R ⁷, R¹⁸, R¹⁹ and R²⁰ are independently selected from H, alkyl, aryl, and aralkyl, and are in particular independently selected from H and C1 -8 alkyl.

Among the ligands of formulae (lla) to (He), particular preference is given in the context of the invention to ligands of formula (lla) and (lib).

For a ligand J of formula (III), the compound of formula (I) has the following structure (lb)

wherein the variables are defined as above, including preferred embodiments.

In the ligand containing Q³, Q⁴ and Q⁵, the following are preferred meanings for these variables.

Q³ to Q⁵ are preferably independently selected from alkyl, aryl, aralkyl, and NR⁵R⁶, wherein any alkyl group, alone or as part of aralkyl, is optionally substituted by one or more substituents selected from F, CI, Br and N(C1-8 alkyl)₂ and wherein any aryl group, alone or as part of another group such as -alkyl-O-aryl, aralkyl or aryloxy, is optionally substituted by one or more substituents selected from C1 -8 alkyl, phenyl, C1 -8 alkoxy, F, CI, Br and N(C1 -8 alkyl)₂.

R⁵ and R^s are preferably independently selected from alkyl, and aralkyl, wherein any alkyl group, alone or as part of aralkyl. is optionally substituted by one or more substituents selected from F, CI, Br and N(C1 -8 alkyl)₂ and wherein any aryl group, alone or as part of aralkyl, is optionally substituted by one or more substituents selected from C1 -8 alkyl, phenyl, C1 -8 alkoxy, F, CI, Br and N(C1 -8 alkyl)₂.

In accordance with a further preferred embodiment, one of Q³ and Q⁵ is defined in accordance with the above preferred embodiments of Q³ to Q⁵, and the other two. i.e. Q³ and Q⁴ or Q⁴ and Q⁵, are both NR R^6a, wherein the groups R⁵ are independently selected from the preferred options listed above, and the two groups R^6a are taken together to form a 5- or 6- membered, preferably 5 membered, saturated or unsaturated heterocycle containing the two N atoms of the NR⁵R^6a groups as heteroatoms. In addition to the groups R⁵, the heterocycle may carry one or more further substituents selected from C1 -8 alkyl, phenyl, C1 -8 alkoxy, F, CI, Br and N(C1 -8 alkyl)₂. Preferably, these further substituents are absent.

In a preferred embodiment, the ligand of formula (III) is selected from one of the following formulae (Ilia) to (Illd):

The variables in these formulae are defined as follows. R to R are independently selected from H, alkyl, cycloalky!, aryl, and aralkyl, wherein any alkyl group, alone or as part of aralkyl. is optionally substituted by one or more substituents selected from F, CI, Br and N(C1 -8 alkyl)₂ and wherein any aryl group, alone or as part of aralkyl. is optionally substituted by one or more substituents selected from C1-8 alkyl, phenyl. C1 -8 alkoxy, F, CI, Br and N(C1 -8 alkyl)₂. Preferably, the aryl group is not substituted or substituted by one or more C1 -8 alkyl groups.

It is preferred that R^2"' to R²⁴ are independently selected from alkyl. aryl and aralkyl. wherein any aryl group, alone or as part of aralkyl. is optionally substituted in the ortho- and/or para- position by one or more C1 -8 alkyl groups. It is particularly preferred that R¹³ and R¹⁴ are independently phenyl, optionally substituted in the ortho- and/or para-position by one or more C1 -8 alkyl groups.

R²¹ to R²⁴ are independently selected from alkyl, cycloalkyl, aryl, and aralkyl, wherein any aryl group, alone or as part of aralkyl, is optionally substituted by one or more substituents selected from C1 -8 alkyl, phenyl, C1 -8 alkoxy, F, CI, Br and N(C1 -8 alkyl)₂. Preferably, the aryl group is not substituted or substituted by one or more C1 -8 alkyl groups.

It is preferred that R²¹ to R²⁴ are independently selected from alkyl, aryl and aralkyl, wherein any aryl group, alone or as part of aralkyl, is optionally substituted in the ortho- and/or para- position by one or more C1 -8 alkyl groups. It is particularly preferred that R²¹ to R²⁴ are independently t-butyl or phenyl.

R²⁵ and R²⁶ are independently selected from H, alkyl, cycloalkyl. aryl. and aralkyl, wherein any alkyl group, alone or as part of aralkyl, is optionally substituted by one or more substituents selected from F , CI, Br and N(C1 -8 alkyl)₂ and wherein any aryl group, alone or as part of aralkyl, is optionally substituted by one or more substituents selected from C1 -8 alkyl, phenyl, C1 -8 alkoxy, F, CI, Br and N(C1-8 alkyl)₂. Preferably, the aryl group is not substituted or substituted by one or more C1 -8 alkyl groups.

It is preferred that R²⁵ and R²⁶ are independently selected from alkyl, aryl and aralkyl, wherein any aryl group, alone or as part of aralkyl, is optionally substituted in the ortho- and/or para- position by one or more C1 -8 alkyl groups, it is particularly preferred that R²⁵ and R²⁶ are independently phenyl, optionally substituted in the ortho- and/or para-position by one or more C1 -8 alkyl groups.

R²⁷ to R³² are independently selected from H, alkyl, cycloalkyl, aryi, and aralkyi, wherein any alkyl group, alone or as part of aralkyi. is optionally substituted by one or more substituents selected from F, CI, Br and N(C1 -8 alkyl)₂ and wherein any aryl group, alone or as part of aralkyi, is optionally substituted by one or more substituents selected from C1 -8 alkyl, phenyl, C1 -8 alkoxy, F, CI, Br and N(C1 -8 alkyl)₂. Preferably R²⁷ to R³² are independently selected from H, alkyl, aryl, and aralkyi, and are in particular independently selected from H and C1 -8 alkyl.

Among the ligands of formulae (Ilia) to (llld), particular preference is given in the context of the invention to ligands of formula (Ilia).

Regarding X¹ and X², it is preferred that these ligands are independently selected from CI. Br, alkyl, -alkyl-SiR^aR^bR°, alkoxy, aryloxy. and aralkyi, wherein any alkyl group, alone or as part of alkoxy or aralky!. is optionally substituted by one or more substituents selected from OH, F, CI, Br, NH₂, NH(C1 -8 alkyl) and N(C1 -8 alkyl)₂, and any aryl group, alone or as part of another group such as aralkyi or aryloxy, is optionally substituted by one or more substituents selected from C1 -8 alkyl, phenyl, C1 -8 alkoxy, OH, F, CI, Br, NH_2> NH(C1 -8 alkyl) and N(C1 -8 alkyl)₂. It is more preferred that X¹ and X² are independently selected from CI, Br, alkyl, aralkyi, and - aikyi-SiR^aR^bR^c. As alkyl, methyl is preferred. As aralkyi, benzyl is preferred. For -alkyl- SiR^aR R^c, it is preferred that -alkyl- is ~CH₂-, and that R^a to R^c are independently selected from methyl and phenyl, and it is particularly preferred that -alkyl- is -CH₂-, and that R^a to R^c are all methyl (Me), or that two of them are methyl and one of them is phenyl (Ph). Thus, in a particularly preferred embodiment, X and X² are independently selected from methyl, benzyl. -CH₂-SiMe₃ and -CH₂-SiMe₂Ph, Most preferred is benzyl.

In the light of the above, particularly preferred complexes in accordance with the invention have the following formula (lc):

wherein the variables M, X¹ , X^~, R , R°, Q¹ and Q^z have the meanings defined above, including preferred definitions thereof. More preferred are the complexes of the formulae (Id) and (le):

In these formulae, the variables M, X¹ , X², R⁷, R⁸, R¹³ and R¹⁴ have the meanings defined above, including preferred definitions thereof. in accordance with a yet furtner preferred embodiment, the complex in accordance with the invention has the formula (If) or (Ig) below.

wherein is selected from 2r and Hf,

X¹ and X² are independently selected from CI, Br, alkyi, alkoxy, aryloxy, aralkyl, and -CH₂- SiR^aR^aR^", wherein R^a to R^c are independently selected from methyl and phenyl, and preferably from alkyl, especially methyl, and aralkyl, especially benzyl, and are most preferably benzyl,

and R^d to R° are independently selected from H and C1 -8 alkyl, and preferably R^d, R^f, R⁹, R . R^j, R¹, R^m and R° are independently selected from C1 -8 alkyl and R^e, R^h, R^k and R" are selected from H and C1 -8 alkyl.

In a further aspect, the invention provides a method for the oligomerization o an olefin, especially ethylene, which method comprises the step of contacting the complex of formula (I), including its preferred embodiments, with an olefin. Preferably, the complex of formula (I) is contacted with the olefin in the presence of an activator.

Generally, the complex in accordance with the invention is used in the form of a catalyst composition. In order to provide a catalyst composition in accordance with the invention which can be conveniently contacted with an olefin as a reactant in an oligomerization reaction, a complex in accordance with the invention (or a mixture of two or more complexes of the invention) can be dissolved or dispersed in a solvent. Examples of suitable solvents include aromatic solvents, such as toluene, benzene and xylene, alkanes, such as the commercially available products Isopar® (Exxon) and Parafol© (SASOL), and cycloalkanes such as cyclohexane.

Alternatively, the complex can be supported on a carrier. This carrier can be, for example, a metal halide or a metal oxide. The metal oxide can be selected from alumina, borla, magnesia, thoria, zirconia, silica, or mixtures thereof. Furthermore, polymeric materials may be used.

Conveniently, the olefin to be oligomerized and the activator can be first charged into the reactor wherein the oligomerization reaction is carried out before the complex or the catalyst composition containing the complex in accordance with the invention is added to the reactor. However, the components (complex(es), activator(s) and reactants) can also be contacted in a different order or can be premixed before injection into the reactor. For example, an activator or an activator and a co-activator can be incorporated together with the complex of formula (I) into the catalyst composition in accordance with the invention, e.g. by combining the complex or complexes and the activator or activators in the solvent contained in the catalyst composition. The activator can be reacted with the complex in accordance with the invention in order to transform the complex into a catalytically active cationic species which offers a coordination site for the olefin to be oligomerized. Generally, the transformation proceeds via removal of one of the ligands X and X² as an anion from the complex of formula (I).

As an activator in accordance with the invention, an alumoxane can be used. An alumoxane component useful as an activator typically is a cyclic or linear oligomeric aluminum compound represented by the general formula -(AI(R')-0)_n- (cyclic) or R'-(AI(R')-0)n-AIR'₂ (linear), wherein R' is independently a C1 -C20 alky! radical, for exampie, methyl, ethyl, propyl, butyl, or pentyl, and "n" is an integer from 3-50. Most preferably, R' is methyl and "n" is at least 4. Preferred examples of alumoxanes are methyl alumoxane (MAO), modified methyl alumoxane (MMAO), ethyl alumoxane. iso-butyl or dry-alumoxane from which all volatiles are removed. The amount of the alumoxane to be reacted with the complex in accordance with the invention generally ranges from 20 mol aluminoxane/mol complex to 10000 mol aluminoxane/mol complex, and preferably from 100 mol aluminoxane/mol complex to 500 mol aluminoxane/mol complex.

Furthermore, ionic activators can be used such as those which contain an anion selected from tetrakis-perfluorophenylborate, tetrakis-perfluoronaphthylborate, tetrakis-perfluorophenyl- aluminate or tetrakis-perfluor-m-xyleneborate. In accordance with a preferred embodiment, the ionic activators combine the above anion with a non-coordinating cation.

Examples of suitable ionic activators are dialkyl ammonium salts of the above anions, such as: di-(i-propyl)ammonium tetrakis(pentafluorophenyl) borate, and dicyclohexylammonium tetrakls(pentafluorophenyl) borate; tri-substituted phosphonium salts of the above anions, such as: triphenyiphosphonium tetrakis(pentafluorophenyl) borate, tri(o-tolyl)phosphonium tetrakis(pentafiuorophenyl) borate, and tri(2,6-dimethylphenyl)phosphonium tetrakis- (pentafluorophenyl) borate; di-substituted oxonium salts of the above anions, such as: diphenyloxonium tetrakis(pentafluorophenyl) borate, di(o-folyl)oxonium tetrakis- (pentafluorophenyl) borate, and di(2,6-dimethylphenyl)oxonium tetrakis(pentafiuorophenyl) borate: di-substituted sulfonium salts of the above anions, such as: diphenylsulfonium tetrakis(pentafluorophenyi) borate, di(o-tolyl)sulfonium tetrakis(pentafiuorophenyl) borate, and bis(2,6-dimethy!phenyl)sulfonium tetrakis(pentafluorophenyi) borate; or imidazoiinlumsalts of the above anions. A further class of activators that can be used are Lewis acid activators, such as triphenyl boron, tris-perfluorophenyl boron, tris-perfluoronaphthylboron, tris-perfluor-m-xyleneboron or tris-perfluorophenyl aluminum.

The amount of the ionic activator or the Lewis acid activator to be reacted with the complex in accordance with the invention generally ranges from 1 mol activator/mol complex to 2 mol activator/mol complex, and preferably from 1 mol activator/mol complex to 1 , 1 mol activator/mol complex.

As a co-activator, a compound can be used which is capable of alkylating the transition metal complex, such that when used in combination with an activator such as a Lewis acid activator or an ionic activator, an active catalyst is formed. Co-activators include alumoxanes, such as methyl alumoxane, modified alumoxanes such as modified methyl alumoxane, aluminum alkyls such trimethyl aluminum, tri-isobutyl aluminum, triethyl aluminum, and tri-isopropyl aluminum and aluminium alkyl halides. The amount of the co-activator is generally in the range of 1 mole to 1000 moles per mole of the complex in accordance with the invention, preferably in the range of 5 mole to 50 moles per mole of the complex in accordance with the invention.

In the method for oiigomerizing an olefin in accordance with the invention, monomers selected from ethylene, propylene or an α-o!efin, or mixtures of these monomers, can be oligomerized Preferably, only ethylene is used as the monomer which is subjected to oligomer!zation.

The method comprises the step of contacting the monomer(s) to be oligomerized with the complex in accordance with the invention or with an activated complex obtainable by contacting the complex in accordance with the invention with an activator, and optionally a co- activator. For example, the monomers can be contacted first with an activator and optionally a co-activator, and subsequently with the complex of the invention, or the monomers are first contacted with the complex in accordance with the invention, and then with the activator and optionally a co-activator.

Frequently, it is advantageous to add a scavenger to the reaction mixture. Scavengers for oligomerization reactions are known in the a t, and generally the same compounds can be used as they are used in polymerization reactions. Examples are aluminium alkyls, such as triisobutylaluminium (TIBA), alumoxanes or combinations thereof. The reaction temperature during the oligomerization reaction is typically in the range of 0°C to 100°C, preferably 20°C to 80 °C and in particular 30 to 70°C. It is an advantage of the complexes in accordance with the invention that they are able to catalyze the oligomerization with a high activity favourably at reduced temperatures. The temperature can also be used to influence the composition of the oiigomerized product. At lower temperatures, the formation of products with a lower degree of oligomerization is favoured, at higher temperatures, a higher ratio of products with a higher degree of oligomerization can be obtained.

An exemplary concentration of the monomer to be oiigomerized, especially ethylene, in the reaction vessel (typically an autoclave) ranges from 0.1 to 5 MPa (1 - 50 bar), preferably from 0.2 to 1 .0 MPa (2 - 10 bar) for a concentration of the complex of the invention of 1 · 10^"5 bis 1^■ 10^"6 M (mol/l).

The complex of the invention is preferably used in a catalyst composition comprising a solvent, and the liquid phase of the catalyst composition can be contacted with the gaseous or liquid monomers. Since ethylene is a preferred monomer, the reaction usually proceeds by contact between the liquid catalyst composition and a gaseous monomer. In this case, the monomer can be conveniently oiigomerized at an absolute pressure in the reactor (usually provided by the monomer) of 0.10 to 5.0 MPa, preferably 0.15 to 1.0 MPa, and more preferably 0.15 to 0.3 MPa. Advantageously, a high activity is achieved at relatively low pressures. The monomer pressure in the reactor can also be used to influence the composition of the oiigomerized product. At lower pressures, the formation of products with a lower degree of oligomerization is favoured, at higher pressures, a higher ratio of products with a higher degree of oligomerization can be obtained.

The complexes and catalyst systems in accordance with the invention allow the production of oligomeric a-olefins with a high selectivity. In particular, the products show a narrow product distribution with respect to the number of monomers contained in the oligomers (i.e. the degree of oligomerization). For the oligomerization of ethylene, 1 -butene. 1 -hexene and 1 - octene, in particular 1 -butene and 1 -hexene can be obtained as main products with a ratio of preferably more than 50 wt% of all oligomers produced. No polymeric side products are obtained. If the distribution of oligomer chain lengths in the product (as determined e.g. via gas chromatography) is described as a Flory-Schulz-distribution (H.H. Nijs, P. A. Jacobs, Journal of Catalysis, 1980, 65, 328-334), the K-value is usually between 0.2 and 0.7, preferably between 0.2 and 0.6. The K-value, as used herein, can be determined as disclosed in "Oligomerization of Ethylene Using New Tridentate Iron Catalysts Bearing alpha-Diimine Ligands with Pendant S and P Donors^", Brooke L. Small, Ray Rios, Eric R. Fernandez, Deidra L. Gerlach, Jason A. Halfen, and Michael J. Carney; Organometallics 2010, 29, 6723-6731.

Also in terms of the structure of the obtained products, the complexes in accordance with the invention ensure a highly selective oligomerization. No incorporation of a-olefins already formed as products into the growing a-olefin chains has been observed. Thus, in the case of ethylene oligomerization, only linear (non-branched) oligomeric a-olefins are formed. Moreover, no isomerization of the products was observed, i.e. α-olefins having one double bond are provided with a high yield.

The complexes in accordance with the invention can be conveniently prepared according to synthetic methods known in the art.

The bidentate ligands containing two coordinating N-Atoms of the complexes in accordance with the invention, such as the aminopyridinato-ligands, are accessible via convenient routes of synthesis at high yields (z.B. Natalie M. Scott. Thomas Schareina, Oleg Tok, Rhett Kempe, Eur. J. Inorg. Chem. 2004, 3297 - 3304 and the literature cited therein). The sterical and electronic properties of such ligands can be easily varied. The preparation of the ligand-metal complexes, such as the aminopyridinato complexes, is well documented especially in the field of polymerization catalysts (e.g. R. Kempe, Eur. J. Inorg. Chem. 2003, 791 -803; W. P. Kretschmer, A. Meetsma. B. Hessen, T. Schmalz, S. Qayyum, R. Kempe. Chem. Eur. J. 2006, 12, 8969 - 8978: W. P. Kretschmer. B. Hessen, A. Noor, N. M. Scott, R. Kempe, J. Organomet. Chem. 2007, 692, 4569 - 4579.: H. Fuhrmann, S. Brenner, P. Arndt, R. Kempe, Inorg. Chem. 1996 35, 6742 - 6745; M. Hafeez, W. P. Kretschmer, R. Kempe. Eur. J. Inorg. Chem. 2011 . 5512 - 5522; Ch. Doring, W. P. Kretschmer. R. Kempe, Eur J. Inorg. Chem. 2010. 2853 - 2860; A. Noor, W. P. Kretschmer. G. Glatz, R. Kempe, Inorg. Chem. 2011. 50, 4598 - 4606; Natalie M. Scott, Thomas Schareina, Oleg Tok, Rhett Kempe, Eur. J. Inorg. Chem. 2004, 3297 - 3304). The preparation of amidinato complexes Is disclosed, e.g . in C. Visser. PhD Thesis, University of Groningen, 2003.

Also the monodentate ligand J can be prepared by methods known in the art. For example, the synthesis of the iminoimdazoiines is described in DE 2916140 A1 via reaction of the corresponding N. N'-diarylalky!-1 .2-diamine with cyanogene bromide in toluene. The 1 ,2- diamine can be prepared either from the corresponding arylamine and 1 ,2-dibromoethane, or via reduction of an a-diimine, the latter being prepared via condensation reaction between the corresponding arylamine and glyoxal. The synthesis of other ketimide ligands is described, e.g., in US 2004/0192541 and the literature cited therein. The coordination of the ligand to a metal center can be easily achieved (e.g. as described in US 2004/0192541 ). Regarding the synthesis and coordination of phosphinimide ligands J, reference can be made e.g. to W.P. Kretschmer, C. Dijkhuis, A. Meetsma, B. Hessen and J. Teuben, Chem. Commun., 2002, 608-609, and to WO 20 1/102989 and to D.W. Stephan, Organometallics 2005, 24, 2548- 2560 and the literature cited in these documents.

As a general route of synthesis for the complexes in accordance with the invention, a complex precursor of formula (V):

wherein Z¹ , L, Z², X¹ and X² are defined as above, including preferred embodiments, and X³ is selected from CI, Br, I, F, H, alkyl, -alkyl-O-alkyl, -a!ky!-O-ary!, a!koxy, aryloxy, aralkyl, -alkyl-SiR^aR^bR°, and NR R², wherein any alkyl group, alone or as part of another group such as -alkyl-O-alkyl, alkoxy or aralkyl, is optionally substituted by one or more substituents selected from OH, F, CI. Br. NH₂, NH(C1 -8 alkyl) and N(C1 -8 alkyl)₂, and any aryl group, alone or as part of another group such as -alkyl-O-aryl, aralkyl or aryloxy, is optionally substituted by one or more substituents selected from C1 -8 alkyl, phenyl, C1 -8 alkoxy, F. CI, Br and N(C1 -8 alkyl)₂, and R^a, R^b and R^c are independently selected from alkyl and aryl;

is reacted with a compound of the formula (Via) or (VI b):

Q Q²C=NH (Via)

Q³Q⁴Q⁵p=NH (VI b), wherein Q¹ to O⁵ are independently defined as above, including preferred embodiments, or with a salt containing an anion of a compound of the formula (Via) or (Vlb) obtained by abstracting the proton indicated these formulae. Typically, the molar ratio of the compounds of formula (V) and (Via) or (VIb) in the reaction is about 1 , such as 0.9 to 1 .1 , and is preferably 1.0. The reaction can be conveniently accomplished in a solvent, e.g. an aromatic solvent such as toluene, at moderate temperatures ranging e.g. from 25 to 70 °C, preferably from 40 to 60 °C. In the compounds of formula (V), X³ is preferably selected from CI, Br, alkyl, alkoxy, aryloxy, and aralkyl, wherein any alkyl group, alone or as part of alkoxy or aralkyl, is optionally substituted by one or more substituents selected from F, CI, Br N(C1 -8 alkyl)₂, and any aryl group, alone or as part of another group such as aralkyl or aryloxy, is optionally substituted by one or more substituents selected from CI -8 alkyl. phenyl, C1 -8 alkoxy, F. CI, Br and N(C1 -8 aikyl)₂. It is more preferred that X³ selected from CI, Br, alkyl, especially methyl, and aralkyl. especially benzyl. Most preferred is benzyl.

Alternatively, the complexes in accordance with the invention can be prepared by reacting a complex precursor of formula (VII):

wherein J, X¹ and X² are defined as above, including preferred embodiments, and X⁴ is selected from CI, Br, I, F, H, alkyl, -alkyi-O-alkyl, -alkyl-O-aryl, alkoxy, aryloxy, aralkyl, -alkyl-SiR^aR^bR^c, and NR¹R², wherein any alkyl group, alone or as part of another group such as -alkyl-O-alkyl, alkoxy or aralkyl, is optionally substituted by one or more substituents selected from OH, F, CI, Br. NH₂, NH(C1 -8 alkyl) and N(C1 -8 alkyl)₂, and any aryl group, alone or as part of another group such as -alkyl-O-aryl, aralkyl or aryloxy, is optionally substituted by one or more substituents selected from C1 -8 alkyl, phenyl, C1 -8 alkoxy, F, CI, Br and N(C1 -8 alkyl)₂, and R^a, R^b and R^c are independently selected from alkyl and aryl;

with a compound of the formula (Villa) or (Vlllb):

(Villa)

or with a salt containing an anion of a compound of the formula (Villa) or (VI I lb) obtained by abstracting the proton indicated these formulae.

A precursor of formula (V) can be conveniently prepared by reacting a compound of formula MX X²X^JX^'\ wherein X¹ to X⁴ are defined as above, including preferred embodiments, with a compound of formula (Villa) or (VI I lb) as defined above, or with a salt containing an anion of a compound of the formula (Villa) or (VI I lb) obtained by abstracting the proton indicated these formulae. M(CH₂SiMe₃). and M(CH₂SiMe₂Ph)₄ (M = Zr, Hf) (M. R. Collier, M. F. Lappert, R. Pearce, J. Chem. Soc, Dalton Trans. 1973, 445.) and tetrabenzylzirconium as exemplary compounds of formula MX X²X³X⁴ have been long known in literature.

A precursor of formula (VII) can be conveniently prepared by reacting a compound of formula MX ^'X²X^:X⁴, wherein X¹ to X^" are defined as above, including preferred embodiments, with a compound of formula (Via) or (VI b) as defined above, or with a salt containing an anion of a compound of the formula (Via) or (VI b) obtained by abstracting the proton indicated these formulae.

In this specification, a number of patent and non-patent documents is cited. The disclosure of these documents, while not considered relevant for the patentability of this invention, is herewith incorporated by reference in its entirety. More specifically, all referenced documents are incorporated by reference to the same extent as if each individual document was specifically and individually indicated to be incorporated by reference.

The invention will now be described by reference to the following examples, which are merely illustrative and are not to be construed as a limitation of the scope of the present invention. Examples

The following abbreviations are used:

Methyl (CH₃)

Ethyl (CH₃CH₂)

/so- Propyl (Me₂CH)

so-Butyl (Me₂CHCH₂)

Benzyl (CH₂Ph)

Methylaluminumoxane [(MeAIO).,^■ (Me₃AI)_{1/3 n}]

dry-Methylaluminoxane [(MeAIO)_n]

Tri-/so-butylaluminum (/-Bu₃AI)

Aminopyridine³

N-(2,6-Diisopropylphenyl)-6-(2,4,6-triisopropylphenyl)pyridin-2-amine

N-(2,6-Diisopropylphenyl)-6-(2,6-dimethylphenyl)pyridin-2-amine^a

N-Mesityl-6-(2,4.6-triisopropylphenyl)pyridin-2-amine^ft

N,6-Dimesitylpyridin-2-amine^a

1 ,3-Bis(2_!6-dimethylphenyl)imidazolidin-2-imine^a

[1 , 1 ':3', 1 "-Terphenyi]-2'-ol^a

Tri-tert- buty!phosphoranimlne⁸

In line with common practice in the art, the H in the abbreviation indicates the parent compound from which the corresponding anionic ligand (e.g. Ap - aminopyridinato ligand) is prepared via abstraction of a proton.

General: All manipulations of air- or moisture-sensitive compounds were carried out under N- using glove-box, standard Schlenk, or vacuum-line techniques. Solvents and reagents were purified by distillation from LiAIH₄, potassium, Na/K alloy, or sodium ketyl of benzophenone under nitrogen immediately before use. Toluene (Aldrich, anhydrous, 99.8%) was passed over columns of A!₂0₃ (Fisher Scientific), BASF R3-1 1 supported Cu oxygen scavenger, and molecular sieves (Aldrich, 4 A). Ethylene (AGA poiymer grade) was passed over BASF R3-1 1 supported Cu oxygen scavenger and molecular sieves (Aldrich, 4 A). NMR spectra were recorded on a Varian Inova 400 (¹H: 400 MHz, ¹³C: 100.5 MHz) or Varian Inova 300 (1 H: 300 MHz, 13C: 75.4 MHz) spectrometer. The ¹H and ¹³C NMR spectra, measured at 26°C, were referenced internally using the residual solvent resonances, and the chemical shifts (δ) reported in ppm. Gel permeation chromatography (GPC) analysis was carried out on a PL- GPC 220 (Agilent, Polymer Laboratories) high temperature chromatographic unit equipped with LS, DP and Rl detectors and two linear mixed bed columns (Olexis, 13-micron particle size) at 150°C using 1 ,2.4-trichlorobenzene as the mobile phase. The samples were prepared by dissolving the polymer (0.05 wt.-%, cone. = 1 mg/mL) in the mobile phase solvent in an external oven and were run without filtration. The molecular weight was referenced to polyethylene (Mw = 520 - 3.200,000 gmol^"1) and polystyrene (Mw = 580-2,800,000 gmoP) standards. The reported values are the average of at least two independent determinations. GC analysis was performed with an Agilent 6850 gas chromatograph equipped with an Agilent 19095J-323E capillary column (HP-5; 5 % phenyl methyl siloxane; 30 m; film 1 .5 pm, diameter 0.53 mm) and a flame ionization detector.

Ν,Ν-Dimethylanilinium (tetrapentafluoropheny!) borate ([PhNMe_?H][B(C₆F₅)₄], abcr GmbH & Co. KG). N.N.N-Trialkylammonium (tetrapentafluoropheny!) borate ([R₂NMeH][B(C₆F₅)4] , R = C₁₆H₃₃ - C_{1 S}H₃₇, 6.2 wt-% B(C₆F₅)₄ in Isopar. DOW Chemicals), Tri- sobutyl aluminum (TIBA, 25 wt-% in toluene, Aldrich), and EURECEN Al 5100-10-toluene (4.9 wt-% in Al, Chemtura Organometallics) were used as received, dry- AO was prepared by removal of volatiles from EURECEN Al 5100. Commercial benzylchloride. 2,6-diphenyl-phenol and zirconium(IV)chloride were used as received from Sigma-Aldrich. The ligand precursor 1 .3- bis-(2,6-dimethyl-phenyl)imidazolidin-2-ylideneamine (DE 2916140 A1 , US 2004/0192541 Al ) and Tri-tert-butylphosphoranimine (US 6239061 Bl). and the metal precursors tetrabenzylzirconium (Zucchini, U.; Albizzati, E.; Giannini, U. J. Organomet. Chem. 1971 , 26, 357), [N-(2,6-diisopropylphenyl)-6-(2,4,6-triisopropylphenyl)pyridin-2-amido]- tribenzylzirconium(IV) (Ap*ZrBz₃, A), [N-mesityl-6-(2,4,6-triisopropylphenyl)pyridin-2-amido]- dibenzylzirconium(IV) (Ap^9MeZrBz₃, B), [N-(2.6-diisopropylphenyl)-6-(2,6- dimethylphenyl)pyridin-2-amido]-tribenzylzirconium(IV) (Ap⁺ZrBz₃, C) [N,6-dimesitylpyndin-2- amido]-tribenzylzirkonium(IV) (Ap^6MeZrBz₃, D), and [N-(2,6-diisopropylphenyl)-6-(2,6- dimethylphenyl)pyridin-2-amido]-tribenzylhafnium(IV) (Ap^'HfBz₃, E) (Noor, A.; Kretschmer, W. P.; Glatz. G., Meetsma, A.; Kempe, R. Eur. J. tnorg. Chem. 2008, 5088) were prepared according to published procedures. Example 1

Synthesis of [1 ,3-bis(2,6-dimethyiphenyl)imida2oi!din-2-imido]-[N-(2,6-diisopropylphenyl)-6- (2,4,6-triisopropylphenyl)pyridin-2-amido]-dibenzylzirconiurn(IV): Ap*[1 ,3-(2',6^'-Me₂C₆H₃)2(CH₂ N)₂C=N]Zr(CH₂Ph)₂; (Precatalyst 1) (cf. Fig. 1)

Ap^*Zr(CH₂Ph)₃ (300 mg, 0.366 mmol) in toluene (5 mL) was added to 1 ,3-bis-(2,6-dimethyl- phenyl)imidazoiidin-2-ylideneamine (107 mg, 0.366 mmol) in toluene (5 mL) at room temperature. The reaction mixture was stirred at 50 °C for 12 h. Toluene was evaporated to dryness and the product was washed with hexane (2 mL) to give the yellow product 1. Suitable crystals for X-ray analysis can be obtained by overlaying a saturated toluene solution with hexane. The structure is shown in Fig. 1. Yield 280 mg (76 %). Elemental analysis for C_s5H,₉N₅Zr (1021.58): calcd. C 76.42. H 7.79, N 6.86: found C 75.29, H 7.68, N 6.67. H N R (300 MHz, C₆D₆, 298 K): δ = 0.80 - 1.28 (m, 30H, H), 1.98 (s. 12H, CH₃), 1.99 - 2.10 (m, 4H, C₆H₅CH₂), 2.59 - 2.72 (m, 3H, H), 2.86 (s, 4H, NCH₂). 328 (sept, 2H, H), 5.50 (dd, 1H, J_HH = 9.7 Hz, H), 6.04 (d 4H, J_HH = 8.7 Hz. o-C₅/~/₅CH₂), 6.38 (dd, 1H_: J_HH = 8.3 Hz. H), 6.76 - 7.15 (m, 18H, H. p-C₆H₅CH₂, m-C₆H₅CH₂, C_eH₃) ppm.¹³C NMR (75.4 MHz. C₆D₆, 298 K): δ = 18.1 (s, 4C, CH₃), 22.9 (s, 2C. CH₃), 23.7 (s, 2C, CH₃), 24.0 (s, 2C, CH₃), 25.5 (s, 2C, CH₃), 26.6 (s, 2C, CH₃), 28.4 (s, 2C, CH), 30.8 (s, 2C, CH), 34.7 (s, 1C, CH), 44.9 (s, 2C, CH₂), 64.3 (s, 2C, PhCH₂), 107.1 (s, 1C, CH), 115.2 (s, 1C, CH), 119.8 (s, 1C. Ph), 121.3 (s, 1C, Ph), 125.5 (s, 1C, C), 127.6 (s, 2C, CH), 1281 (s, 4C, Ph), 128.3 (s, 4C, Ph), 128.9 (s, 2C, CH), 129.2 (s, 2C, CH), 129.9 (s, 2C, C), 135.6 (s, 1C, C), 137.5 (s, 6C, C₆H₃), 138.3 (s, 2C, NC), 139.6 (s, 1C, C), 144.0 (s, 1C, C), 145.6 (s, 2C, C), 146.7 (s, 2C. C), 147.2 (s, 1C, C), 147.6 (s, 2C, C), 149.8 (s, 1C, C), 157.4 (s, 1C, C), 168.3 (s, 1C, CN) ppm. Example 2

Synthesis of [1 ,3-bis(2,6-dimethylphenyl)imidazolidine-2-imido]-[N-rnesityl-6-(2,4,6- triisopropylphenyl)pyridin-2-amido]-dibenzylzirconium(IV): Ap^9fl'e[1 ,3-(2\6^!-Me₂C₅H₃)₂(CH₂ N)₂C=N]Zr(CH₂Ph)₂ (Precatalyst 2).

Toluene (30 mL) was added to Ap^{9 e}Zr(CH₂Ph)₃ (300 mg, 0.39 mmol) and 1 ,3-bis-(2.6- dimethyl-phenyl)imidazolidine-2-ylideneamine (113 mg, 0.39 mmol) at room temperature. The resulting solution was stirred for 3 h at 80 °C with continous stirring. Toluene was evaporated to dryness and the resulting residue was washed with hexane (2 mL) affording 2 as a yellow solid. X-ray quality crystals can be obtained by adding a few drops of THF to a concentrated toluene solution at room temperature. Yield 310 mg (82 %). Elemental analysis for C62H_{73 5}Zr (979.50): calcd. C 76.02, H 7.51, N 7.15; found C 76.53, H 7.79, N 6.69.¹H NMR (300 MHz, C₆D₆.298 K): δ = 1.07 (d, 6H, J_HH = 7.4 Hz, H), 1.16 (d, J_HH = 7.7 Hz, H), 1.25 (d, 6H, J_HH = 7.4 Hz, H), 1.51 (d, 2H, J_HH = 10.2 Hz, C₆H₅CH₂), 1.60 (s, 5H, H), 1.67 (d, 2H, J_HH = 10.2 Hz, C₆H₅CH₂), 2.01 (s, 12H, CH₃), 2.20 (s, 3H, H), 2.75 (sept, 1H, H), 2.90 (s.4H, NCH₂), 3.15 (sept, 2H, H), 5.35 (d, 1H, J_HH = 9.3 Hz, H), 6.00 (d, 4H, J_HH = 8.3 Hz, o-C₆H₅CH₂), 6.27 (d, 1H, J_HH = 8.0 Hz, H), 6.70 - 7,16 (m, 17H, H, m-C₆H₅CH_2l p-C₆H₅CH₂) ppm. ¹³C NMR (75.4 MHz, C₆D₆, 298 K): δ = 18.3 (s, 4C, CH₃), 19.0 (s, 2C, CH₃), 21.2 (s, 1C, CH₃), 22.6 (s, 2C, CH₃), 24.5 (s, 2C, CH₃), 26.6 (s, 2C. CH₃), 31.0 (s, 2C, CH), 35.0 (s, 1C, CH), 45.2 (s, 2C, NCH₂), 63.1 (s, 2C, PhCH₂), 104.9 (s, 1C, CH), 115.1 (s, 1C, CH), 120.7 (s.1C, Ph), 121.4 (s, 1C, Ph), 125.7 (s, 1C, C), 127.7 (s, 2C, CH), 128.1 (s, 4C, Ph), 128.4 (s, 4C, Ph), 129.0 (s, 2C. CH), 129.3 (s, 2C, C), 129.4 (s, 1C, CH), 133.3 (s, 1C, C), 134.4 (s, 2C, C), 136.1 (s, 1C, C), 137.9 (s, 6C. C₆H₃), 138.0 (s, 2C, NC), 140.1 (s, 1C, C), 144.6 (s, 1C. C), 145.6 (s, 1C, C), 146.0 (s, 2C, C), 147.2 (s, 2C, C), 149.9 (s, 1C, C), 157.1 (s, 1C, C), 167.7 (s, 1C, CN) ppm. Example 3

Synthesis of [1 .3-bis(2,6-dimethylphenyl)imidazolidine-2-imido]-[N-(2,6-diisopropylphenyl)-6- (2.6-dimethylphenyl)pyridin-2-amido]-dibenzylzirconium(IV); Ap⁺[1 ,3-(2',6'-Me₂C₆H3)2(CH2 N)₂C=N]Zr(CH₂Ph)₂ (Precatalyst 3) .

To a toluene solution (7 mL) containing Ap⁺Zr(CH₂Ph)₃ (202 mg , 0.28 mmol) was added 1 ,3- bis-(2,6-dimethyi-phenyl)imidazolidine-2-ylideneamine (82 mg, 0.28 mmol) in toluene (7 mL) at room temperature. The reaction mixture was stirred at 50 °C for 12 h. Toluene was evaporated to dryness and the product was washed with hexane (2 mL) to give the yellow product 3. Suitable crystals for X-ray analysis can be obtained by overlaying a saturated toluene solution with hexane. Yield 241 mg (93 %). Elemental analysis for C₅eH₆₅N₅Zr (923.39): calcd. C 74.44, H 7.10, N 7.58; found C 75.35. H 6,83, N 7.57. ¹ H NMR (300 MHz, C₆D₆, 298 K): δ = 0.91 (d, 6H. J_HH = 7.4 Hz, H), 1 .00 (d, 6H, J_HH = 7.4 Hz, H), 2.05 (s, 12H, CH₃), 2.08 (d, 2H. J_HH = 10.6 Hz, C₆H₅CH₂), 2.21 (d, 2H, J_HH = 10.6 Hz, C₆H₅CH₂), 2.29 (s, 6H, H), 2.72 (sept, 2H, H) , 2.93 (s, 4H, NCH₂), 5.51 (d, 1 H, J_HH = 9.1 Hz, H) , 6.09 (d, 1 H, J_HH = 8.1 Hz, H), 6.19 (d, 4H, J_HH = 8.4 Hz, o-C₆H₅CH₂), 6.83 -- 7.20 (m, 19H, H, C₆H₃, p- C₆H₅CH₂, m-C₆H₅CH₂) ppm. ¹³C NMR (75.4 MHz, C₆D₆, 298 K) : δ = 18.3 (s, 4C . CH₃), 20.7 (s, 2C. CH₃), 24.8 (s, 2C, CH₃), 25 2 (s, 2C, CH₃), 28.3 (s, 2C, CH), 45.7 (s, 20, CH₂) , 65.9 (s, 2C, CH₂), 106.5 (s, 1 C, CH), 1 13.3 (s, 1 C, CH), 120.5 (s, 1 C, CH), 124.2 (s, 1 C, CH), 125.5 (s, 1 C, C), 1 27.4 (s, 2C, CH), 128. 1 (s, 3C. CH), 128.3 (s, 4C. CH), 1 28.5 (s, 4C, CH), 129.0 (s, 2C, CH), 129.5 (s, 2C, C), 1 34.8 (s, 1 C, C), 1 36.7 (s, 2C, C), 137.8 (s, 6C, C₆H₃), 1 38.2 (s, 2C, NC), 140.8 (s, 1 C, C), 143.0 (s. 1 C, C) , 145.0 (s, 2C, C), 146.7 (s, 2C, C), 149.8 (s, 1 C, C), 156.8 (s, 1 C. C), 172.9 (s, 1 C, CN) ppm.

Example 4

Synthesis of [Tri-tert-butylphosphoranimido]-[N.6-dimesitylpyridin-2-amido]-dibenzylzirkonium (IV); Ap^6Me[£-Bu₃P=N]Zr(CH₂Ph)₂ (Precatalyst 4)

Ap^6MeZr(CH₂Ph)₃ (35 mg. 0.05 mmol) was added to a charged NMR tube with Tri-tert- butylphosphoranimine (10.2 mg, 0.05 mmol) in C₆D₆ (0.7 mL) at room temperature. The reaction mixture was shaken for 5 days and measured. ¹ H NMR (300 MHz. CeDg, 298 K): δ = 0.71 - 0.93 (d, 27H, ³J_P-H = 1 3.0 Hz, f-Bu). 2.19 (s, 3H, Me), 2.23 (s, 6H, Me), 2.35 (s, 9H, Me), 2.42 (d, 2H , J = 2.1 Hz CH₂), 2.77 (d, 2H, J = 2 Hz CH₂), 5.64 (d, 1 H, J = 9.1 Hz CH), 6.18 (d, 1 H, J = 7.0 Hz CH). 6.41 (d, 1 H, J = 7.6 Hz CH), 6.76 - 7.12 (m, 14H, Ph) ppm. ¹³C NMR (75.4 MHz, C₆D₆, 298 K): δ = 18.9 (CH₃, 2C), 20.2 (CH₃, 2C), 20.6 (CH₃, 2C), 28.9 (CH₃. 3C),38.9 (C_q), 64.5 (CH₂). 102.1 (CH_arom), 1 13.0 (C_arom), 120.4 (C_arom), 128.9 (Carom, 6C), 129.5 (C_q, 1 C), 133.4 (C_ar0m), 133.9 (C_arom, 3C), 137,4 (C_arom), 140.5 (C_arom), 145.1 (C_arom), 157.8 (C_arom), 167.5 (NCN) ppm.

Example 5

Synthesis of [1 ,3-bis(2,6-dimethylphenyl)imidazolidin-2-imido]-[N-(2,6-diisopropylphenyl)-6- (2,6-dimethylphenyl)pyridin-2-amido]-dibenzylhafnium(IV); Ap⁺[1 ,3-(2',6'-Me₂C₆H₃)₂(CH₂ N)₂C=N]Hf(CH₂Ph)₂ (Precatalyst 5)

To a toluene solution (7 mL) containing Ap⁺Hf(CH₂Ph)₃ (226 mg, 0.28 mmol) was added 1 ,3- Bis-(2,6-dimethyl-phenyl)imidazolidin-2-ylideneamine (82 mg, 0.28 mmol) in toluene (7 mL) at room temperature. The reaction mixture was stirred at 50 °C for 12 h. Toluene was evaporated to dryness and the product was washed with hexane (2 mL) to give the yellow product 5 Suitable crystals for X-ray analysis can be obtained by overlaying a saturated toluene solution with hexane. Yield 200 mg (70 %). Elemental analysis for C5₈H₆₅N₆Hf (1010.66): calcd. C 68.93, H 6.48, N 6.93: found C 65.25. H 6.53, N 6.71 . ¹H NMR (300 MHz, C₆D_6i 298 K): δ = 0.93 (d, 6H, J_HH = 4.9 Hz, H^{22 23}), 1 .08 (d, 6H, J_HH = 4.9 Hz, H^1S'²⁰), 1 .60 (d, 2H, J_HH = 8.5 Hz, C₆H₅CH₂), 1 .69 (d, 2H, J_HH = 8.5 Hz, C₆H₅CH₂), 2.29 (s, 6H, H^24,25), 2.28 (s, 12H, CH₃), 2.94 (s, 4H, NCH₂), 3.15 (sept, 2H. H¹⁸'²¹), 5.54 (d, 1 H, J_HH = 6.5 Hz, H¹⁰), 5.96 (d, 1 H, J_HH = 5.5 Hz, H⁸), 6.49 (d, 4H. J_HH = 6.5 Hz, o-C₆W₅CH₂), 6.72 - 7.26 (m, 19H. 1^ 1 ,2,3,9,14,15,16^ _Q^ p.Q^QH^ _m_c₆/- ₅CH₂) ppm. ³C NMR (75.4 MHz, C₆D₆, 298 K): δ = 20.8 (s, 4C, CH₃), 21.4 (s, 2C, CH₃), 23.9 (s, 2C, CH₃), 25.4 (s, 2C, CH₃), 28.8 (s, 2C, CH), 44.8 (s, 2C, CH₂), 78.6 (s, 2C, CH₂), 100.2 (s, 1 C, CH), 105.7 (s, 1 C, CH), 1 1 1.6 (s, 1 C, CH), 120.7 (s, 1 C, CH), 122.8 (s, 1 C, CH), 124.1 (s, 1 C, C), 124.3 (s, 2C, CH), 127.2 (s, 3C, CH), 127.8 (s, 4C, CH), 128.1 (s, 4C, CH), 128.3 (s, 2C, CH), 129.1 (s, 2C, C), 129.3 (s, 1 C, C), 136.4 (s, 2C. C), 137.8 (s, 6C, C₆H₃), 139.2 (s, 2C, NC), 141.7 (s, 1 C, C), 142.5 (s, 1 C, C), 144.9 (s, 2C, C), 146.5 (s, 2C, C), 149.3 (s, 1 C, C), 157.8 (s, 1 C, C), 173.1 (s, 1 C, CN) ppm.

Comparative Example 1

Synthesis of [(1 ,1 ':3', 1 "-terphenyl)-2'-oxido]-[N-(2,6-diisopropylphenyl)-6-(2,6-dimethylphenyl)- pyridine-2-amido]-dibenzylzirconium(IV); Ap⁺(2.6-Ph₂C₆H₃0)Zr(CH₂Ph)₂ (Precatalyst F).

Toluene (10 mL) was added to Ap⁺Zr(CH₂Ph)₃ (100 mg, 0.138 mmol) and 2.6-diphenylphenol (34 mg, 0.138 mmol) at room temperature. The reaction mixture was stirred at 80 °C for 12 h. Toluene was evaporated to dryness and the product was washed with hexane (5 mL) affording F quantitatively as a light yellow spectroscopically pure compound. Suitable crystals for X-ray analysis can be obtained by refluxing a saturated toluene solution for 15 min. and subsequent cooling the solution to room temperature. Yield 1 14 mg (94 %). Elemental analysis for C₅₇H₅₆N₂OZr (876.29): calcd. C 78.13. H 6.44, N 3.20; found C 77.85, H 6.57. N 3.13. ¹H NMR (300 MHz, C₆D₆, 298 K): δ = 0.85 (d, 3H, J_HH = 7.5 Hz, H), 1.00 (d, 3H, J_HH = 7.6 Hz, H), 1 .14 (dd, J_HH = 7.5, 7.4 Hz, 6H, H), 1 .95 - 2.03 (m, 10H, H,C₆H₅CH₂), 3.22 (sept, 1 H, H), 3.55 (sept, 1 H, H), 5.63 (d, J_HH = 8.0 Hz, 1 H, H), 6.16 (d, J_HH = 8.7 Hz, 1 H, H), 6.34 (d, J_HH = 10.8 Hz. 4H. o-C₆H₅CH₂), 6.67 (t, J_HH = 7.3 Hz. 2 H. p-C₆H₅CH₂), 6.75 - 7.1 1 (m, 24H. H, m-C₆H₅CH₂, Ph₂C₆H₃) ppm. ¹³C NMR (75.4 MHz. C₆D₆, 298 K): δ = 19.9 (s, 2C, CH₃), 23 9 (s, 2C, CH₃), 25.4 (s, 2C. CH₃), 28.9 (s. 2C, CH), 80.1 (s, 2C, CH₂), 105.6 (s, 1 C, CH),

1 14.5 (s, 1 C, CH), 121 .6 (s, 1 C, CH), 122.2 (s, 1 C, CH), 124.1 (s, 1 C, CH), 124.4 (s, 2C, CH),

124.6 (s, 1 C. C), 127.3 (s, 1 C. C), 127.7 (s, 3C, CH), 128.1 (s, 4C, CH), 128.2 (s. 2C. CH), 128.4 (s, 4C, CH). 128.8 (s, 2C, CH). 128.9 (s, 4C, CH), 129.8 (s, 4C, CH), 130.2 (s, 2C, CH),

132.7 (s, 2C. C), 135.8 (s, 1 C, C), 137.7 (s. 1 C, C), 139 8 (s, 2C, C), 142.9 (s, 1 C, C), 143.1 (s, 1 C, C), 144.7 (s, 1 C, C), 147.9 (s, 1 C, C), 156.1 (s, 1 C. C), 160.4 (s, 1 C, C), 172.7 (s, 1 C, C) ppm.

Comparative Example 2

Ethylene polymerization experiments for Runs 1 to 7 (comparative)

The catalytic ethylene oligomerization reactions were performed in a 250 mL glass autoclave (Buechi) in semi-batch mode (ethylene was added by replenishing flow to keep the pressure constant). The reactor was ethylene flow controlled and equipped with separated toluene, precatalyst and activator injection systems. During a oligomerization run the pressure and the reactor temperature were kept constant while the ethylene flow was monitored continuously. In a typical semi-batch experiment, the autoclave was evacuated and heated for 1 h at 80 °C prior to use. The reactor was then brought to desired temperature, stirred at 1000 rpm and charged with 150 mL of toluene. After pressurizing with ethylene to reach 0.2 MPa (2 bar) total pressure the autoclave was equilibrated for 10 min. Successive co-catalyst solution, activator, and 1 mL of a 0.002 M precatalyst stock solution in toluene was injected, to start the reaction. After 15 min reaction time the reactor was vented and the residual aluminum alkyls were destroyed by addition of 50 mL of ethanol. Polymeric product was collected, stirred for 30 min in acidified ethanol and rinsed with ethanol and acetone on a glass frit. The polymer was initially dried on air and subsequently in vacuum at 80°C.

The results are listed in the following table 1 :

Table 1. Ethylene polymerization experiments with precatalysts A - C and E - F (comparative).

Entry Precat. T nri^poi. Activity M_n M_w/M_n

[°C] [g] [kg_PEmol_cat ^"V¹ ar^"1] [kgmor¹]

1 A 50 1.67 1670 8.4 2.5

2 B 50 4.20 4200 6.5 2.5

3 C 50 4.50 4500 6.2 3.0

4 E 50 0.07 70 2.4 1 .4

5 F 30 traces n.d. n.d. n.d.

6 F 50 0.10 98 156525 21.2

7 F 70 0.13 128 1 17274 40.1

Conditions for all runs: precatalyst: 2.0 μιηοΙ; activator 2.2 ymol ([R₂NMeH][B(C₆F5)4], Zr/B = 1/1 .1 ); toluene: 150 mL; p(ethylene) = 0.2 Pa ; t = 15 min.

Example 6

General description of the ethylene oligomerization experiments for Runs 8 - 22 according to the invention

The catalytic ethylene oligomerization reactions were performed in a 250 mL glass autoclave (Buechi) in semi-batch mode (ethylene was added by replenishing flow to keep the pressure constant). The reactor was ethylene flow controlled and equipped with separated toluene, precatalyst and activator injection systems. During an oligomerization run the pressure and the reactor temperature were kept constant while the ethylene flow was monitored continuously. In a typical semibatch experiment, the autoclave was evacuated and heated for 1 h at 80 °C prior to use. The reactor was then brought to the desired temperature, stirred at 1000 rpm and charged with 150 ml_ of toluene together with the activator Ν,Ν,Ν- trialkylammonium(tetrapentafluoro-phenyl)borate (220 nmol, 2.45 mg 1 1 % stock solution in Isopar), the required amount of TIB A (0.1 ml_ of a 1 .0 M solution of TIBA (tri- isobutylaluminium, Zr/AI = 1/500) and 1 g cumene was added as an internal standard, unless mentioned different in the text. After pressurizing with ethylene to reach the desired total pressure, the autoclave was equilibrated for 5 min. Subsequently, 1 mL of a 0.0002 M catalyst stock solution in toluene was injected to start the reaction. During the run, the ethylene pressure was kept constant to within 0.01 MPa of the initial pressure by replenishing the gas flow. After a 15 min reaction time, the reactor was vented and the solution was then analyzed by GC to determinate the activity and the product distribution.

Example 7

General description of ethylene oligomerization experiments for Run 23

The catalytic ethylene oligomerization reactions were performed in a 250 mL glass autoclave (Buechi) in semi-batch mode (ethylene was added by replenishing flow to keep the pressure constant). The reactor was ethylene flow controlled and equipped with separated toiuene, precatalyst and activator injection systems. During an oligomerization run the pressure and the reactor temperature were kept constant while the ethylene flow was monitored continuously. In a typical semibatch experiment, the autoclave was evacuated and heated for 1 h at 80 °C prior to use. The reactor was then brought to the desired temperature, stirred at 1000 rpm and charged with 150 mL of toluene together with the activator d-MAO (1 1 .6 mg, 0.2 mmol Zr/AI = 1000). Cumene (1 g) was added as an internal standard. After pressurizing with ethylene to reach a total pressure of 0.2 MPa (2 bar), the autoclave was equilibrated for 5 min. Subsequently, 1 mL of a 0.0002 M catalyst stock solution in toluene was injected to start the reaction. During the run, the ethylene pressure was kept constant to within 0.01 MPa of the initial pressure by replenishing the gas flow. After a 15 min reaction time, the reactor was vented and the solution was then analyzed by GC to determinate the activity and the product distribution. Table 2. Ethylene oligomerization experiments with precatalysts 1 to 5, according to the invention.

Conditions for all runs, deviations are specifically indicated (cf. footnotes ^b, ^c, ^d and ^e): precatalyst: 0.2 pmol; activator 0.22 pmol ([R₂NMeH][B(C₆F₅)₄], Zr/B = 1/1 .1 ); scavenger: 100 pmol (TIBA): toluene: 150 mL; p(ethylene) = 0,2 MPa ; t = 15 min; yield by ethylen-flow; wt% and purity by GC- and GC-MS-analysis. p(ethylene) = 0.1 MPa. ^cp(ethylene) = 0.4 MPa. ^d precatalyst: 2.0 pmol; activator 2.2 pmol ([R₂NMeH][B(C₆F₅)4], Zr/B = 1/1.1 ); scavenger: 200 pmol (TIBA). ^eactivator d-MAO (Zr/AI = 1/1000).

Claims

Claims

1 . A complex of formula (I):

wherein

M is a metal selected from Zr and Hf;

X¹ and X² are independently selected from CI, Br, I, F, H, alkyl, -alkyl-O-alkyl, -alkyl-O- aryl, alkoxy, aryloxy, aralkyi, -alkyl-SiR^aR^bR^c, and NR¹R², wherein any alkyl group is optionally substituted by one or more substituents selected from OH, F, CI, Br, NH₂, NH(C1 -8 alkyl) and N(C1 -8 alkyl)₂, and any aryl group is optionally substituted by one or more substituents selected from C1 -8 alkyl, phenyl, C1 -8 alkoxy, OH, F, CI, Br, NH₂, NH(C1-8 alkyl) and N(C1-8 alkyl)₂;

L is selected from CZ³, N, and PR³R⁴;

Z¹ and Z² are independently selected from alkyl, cycloalkyl, heterocycloalkyl, alkenyl, aryl, heteroaryl, aralkyi, -alkyl-O-alkyl, -alkyl-O-aryl, wherein any alkyl group, alone or as part of another group, and any alkenyl group is optionally substituted by one or more substituents selected from F, CI, Br and N(C1 -8 alkyl)₂ and any aryl group, alone or as part of another group, and any heteroaryl group is optionally substituted by one or more substituents selected from C1-8 alkyl, phenyl, C1 -8 alkoxy, F, CI, Br and N(C1 -8 alkyl )₂;

Z³ is selected from H, alkyl, cycloalkyl, heterocycloalkyl, alkenyl, alkoxy, aryl, aryloxy, heteroaryl, aralkyi, -alkyl-O-alkyl, -alkyl-O-aryl, F, CI, Br, NR' R², and PR³R⁴, wherein any alkyl group, alone or as part of another group, and any alkenyl group is optionally substituted by one or more substituents selected from F, CI, Br and N(C1 -8 alkyl)₂ and wherein any aryl group, alone or as part of another group, and any heteroaryl group is optionally substituted by one or more substituents selected from C1 -8 alkyl, phenyl, C1-8 alkoxy, F, CI, Br and N(C1 -8 alky!)₂;

or any suitable groups Z¹ and Z³ or Z² and Z³ as defined above may be linked to form an optionally substituted five- to seven-membered heterocyclic ring incorporating the nitrogen atom to which Z is attached or the nitrogen atom to which Z² is attached; J is selected from a ligand of the formula (II) or (III):

wherein

Q¹ to Q⁵ are independently selected from alkyl, cycloalkyl, heterocycloalkyl, alkenyl, alkoxy, aryl, aryloxy, heteroaryl, aralkyl, -alkyl-O-alkyl, -alkyl-O-aryl and NR⁵R⁶. wherein any alkyl group, alone or as part of another group, and any alkenyl group is optionally substituted by one or more substituents selected from F, CI, Br and N(C1-8 alkyl)₂ and wherein any aryl group , alone or as part of another group, is optionally substituted by one or more substituents selected from CI -8 alkyl, phenyl, C1-8 alkoxy, F, CI, Br and N(C1-8 alky!)₂;

or any suitable groups Q and Q² as defined above may be linked to form a five- to seven-membered, carbocyclic or heterocyclic, saturated or unsaturated ring together with the carbon atom to which they are attached, or any suitable groups Q³ and Q⁴ as defined above or Q⁴ and Q⁵ as defined above may be linked to form a five- to seven-membered, heterocyclic, saturated or unsaturated ring together with the P-atom to which they are attached;

R.^a, R^b and R^c are independently selected from alkyl and aryl; and

R¹ , R², R³, R⁴, R⁵ and R⁶ are independently selected from H, alkyl, cycloalkyl, alkenyl, aryl, and aralkyl, wherein any alkyl group, alone or as part of aralkyl, is optionally substituted by one or more substituents selected from F, CI, Br and N(C1 -8 alkyl)₂ and wherein any aryl group, alone or as part of aralkyl, is optionally substituted by one or more substituents selected from C1 -8 alkyl, phenyl, C1 -8 alkoxy, F, CI, Br and N(C1 -8 alkyl)₂;

or any suitable groups R¹ and R² as defined above, R³ and R⁴ as defined above or R⁵ and R⁶ as defined above may be linked to form an optionally substituted five- or six- membered heterocyclic ring including the N or P atom to which they are attached; or, where Q¹ and Q², Q³ and Q⁴ or Q⁴ and Q⁵ are NR⁵R°, two groups R⁵ or two groups R⁶ as defined above may be linked to form an optionally substituted saturated or unsaturated heterocycle including the two N atoms of the groups NR⁵R⁶;

or one of Q¹ to Cf as defined above may be linked with one of Z¹ or Z² as defined above to form a metallacycle including M.

2. The complex of formula (I) in accordance with claim 1 , wherein L is CZ³.

3. The complex of formula (I) in accordance with claim 1 , wherein the ligand containing Z¹ , L and Z² is a ligand is selected from the following formulae (IVa) to (IVc)

wherein R⁷, R⁸, and R⁹ are independently selected from alkyl, cycloalkyl, aryl, and aralkyl, wherein any aryl group, alone or as part of aralkyl, is optionally substituted by one or more substituents selected from C1 -8 alkyl, phenyl, C1 -8 alkoxy, F, CI, Br and N(C1 -8 alkyl )₂;

R ⁰ is selected from H, alkyl, cycloalkyl, aryl, and aralkyl, wherein any aryl group, alone or as part of aralkyl, is optionally substituted by one or more substituents selected from C1 -8 alkyl, phenyl, C1 -8 alkoxy, F, CI, Br and N(C1 -8 alkyl)₂. Preferably, the aryl group is not substituted or substituted by one or more C1 -8 alkyl groups; and

R¹¹ and R¹² are independently selected from H, alkyl, cycloalkyl, aryl, and aralkyl, wherein any alkyl group, alone or as part of aralkyl, is optionally substituted by one or more substituents selected from F, CI, Br and N(C1 -8 alkyl)₂ and wherein any aryl group, alone or as part of aralkyl, is optionally substituted by one or more substituents selected from C1 -8 alkyl, phenyl, C1 -8 alkoxy, F, CI, Br and N(C1-8 alky!)₂: or R¹¹ and R ² as defined above may be linked to form an optionally substituted five- or six-membered heterocyclic ring including the N atom to which they are attached.

4. The complex of formula (I) in accordance with claim 3, wherein the ligand containing Z¹ , L and Z² is a ligand of formula (IVa)

The complex of formula (I) in accordance with any of claims 1 to 4, wherein J is a ligand of formula (II).

The complex of claim 5, wherein J is a ligand of formula (lla) or (lib):

wherein R¹³ and R¹⁴ are independently selected from H, alkyl, cycloalkyl, aryl, and aralkyi, wherein any alkyl group, alone or as part of aralkyi, is optionally substituted by one or more substituents selected from F, CI, Br and N(C1-8 alkyl)₂ and wherein any aryl group, alone or as part of aralkyi, is optionally substituted by one or more substituents selected from C1-8 alkyl, phenyl, C1 -8 alkoxy, F, CI, Br and N(C1-8 alkyl)₂.

7. The complex of formula (!) in accordance with any of claims 1 to 4, wherein J is a ligand of formula (III).

8. The complex of formula (I) in accordance with any of claims 1 to 7, wherein X¹ and X² are independently selected from CI, Br, alkyl, -alkyl-SiR^aR^bR°, and aralkyi.

9. A method for the oligomerization of an olefin, which comprises a step of contacting the complex of formula (I) as defined in any of claims 1 to 8, with an olefin.

10. The method of claim 9, wherein the complex of formula (I) is contacted with the olefin in the presence of an activator.

1 1. The method of claim 9 or 10, wherein the olefin is ethylene.