WO2019060479A1

WO2019060479A1 - Cleavage of methyldisilanes to methylmonosilanes

Info

Publication number: WO2019060479A1
Application number: PCT/US2018/051851
Authority: WO
Inventors: Norbert Auner; Tobias SANTOWSKI; Alexander G. STURM
Original assignee: Momentive Performance Materials Inc.
Priority date: 2017-09-20
Filing date: 2018-09-20
Publication date: 2019-03-28

Abstract

The invention relates to a process for the manufacture of methylmonosilanes comprising the step of subjecting one or more methyldisilanes to the cleavage reaction of the silicon-silicon bond, and optionally a step of separating the resulting methylmonosilanes.

Description

Cleavage of Methyldisilanes to Methylmonosilanes TECHNICAL FIELD

The present invention relates to the technical field of the production of methylmonosilanes, in particular to the production of mono-, di- and trimethylmonosilanes, more specifically to a process for the production of mono-, di- and trimethylmonosilanes starting from methyldisilanes by a cleavage reaction of the silicon-silicon bond. BACKGROUND OF THE INVENTION

Methylchlorosilanes and methylhydridosilanes are highly useful starting materials in synthetic organosilicon chemistry, and therefore constitute an industrially valuable class of compounds. I n particular, methylsilanes bearing both chloro- and hydrido substituents constitute attractive starting materials in synthesis due to their bifunctional nature, which means they have functional groups of different reactivities. The chloride ligand is a better leaving group than the hydride group and allows, for instance, the controlled addition of further monomeric or oligomeric siloxane units with retention of the Si-H bond under mild conditions, thereby rendering said chlorohydridosilanes useful as blocking and coupling agents in the synthesis of defined oligo- and polysiloxanes.

Such compounds generally find a wide range of applications, for instance for the manufacture of adhesives, sealants, mouldings, composites and resins for example in the fields of electronics, automotive, construction and many more.

The Si-H moieties present in chlorosilanes can be utilized for post-synthesis modifications and functionalisations, for instance for the introduction of organic residues to polyorganosiloxanes or for cross-linking by hydrosilylation reactions, which is desirable in various kinds of compositions containing polyorganosiloxanes.

Synthesis of functionalized polysiloxanes starting with transformations via the Si-H bond(s) followed by hydrolysis or alcoholysis of the Si-CI bond(s) and optionally condensation for the formation of polysiloxanes is also viable.

Although there is a high demand for such bifunctional silanes having both Si-H and Si-CI bonds, there is no practical, economically reasonable and sustainable industrial process for the synthesis of such building blocks disclosed yet. The production of methylsilanes by Si-Si-bond cleavage of disilanes has been reported by Lewis and Neely in WO 2013/101618 A1 (US 8,697,901 B2) and WO 2013/101619 A1 (US 8,637,695 B2) . In these publications, the hydrochlorinative cleavage of the disilanes of the Direct Process Residue (DPR) requires the presence of heterocyclic amines or group 15 quarternary onium compounds serving as catalysts. The scope of starting materials in above- cited publications is restricted to perchlorinated methyl disilanes.

In EP 0574912 B1 (B. Pachaly, A. Schinabeck; 1993) a process for the preparation of methylchlorosilanes from the high-boiling residue from the Direct Process by Si-Si-bond cleavage with hydrogen chloride and a catalyst which remains in the reaction mixture, usually a tertiary amine, is described.

In US 4,291 , 167, Allain and Maniscalco disclose a process for the reduction of tetramethyldichlorodisilane (CIMe₂Si-SiMe₂CI) to tetramethyldisilane (HMe₂Si-SiMe₂H) with mixtures of NaH and NaBH₄ in tetraethylene glycol diethyl ether.

US 5 288 892 describes a process for separating methylchlorosilanes from high boiling residues from the methylchlorosilane synthesis.

DD 274 227 concerns a process for the production of chlor-methyl-silanes from chlor-methyl- disilanes.

PROBLEM TO BE SOLVED

The problem to be solved by the present invention is the provision of a process for the production of, in particular, methylchloro- and methylhydridomonosilanes from methyldisilanes by Si-Si-bond cleavage, wherein the methylhydridodisilanes can be preferably obtained by hydrogenation of methylchlorodisilanes from the Rochow Mtiller disilane residue. Further, it is the object of present invention to provide a process with improved product yields, product purity, product selectivity of the conversion, convenience of the work-up procedure, ease of handling of the reagents and cost efficiency of the process. The invention in particular addresses the provision of such an improved process in which high proportions of methylhydridomonosilanes can be obtained. According to the present invention this problem is solved as described in the following .

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a process for the production of methylmonosilanes starting from the corresponding methyldisilanes by cleavage of the silicon-silicon bond. Subject of the invention is a process for the manufacture of methylmonosilanes of the general formula (I):

MexSiHyClz (I), wherein

x = 1 to 3,

y = O to 3,

z = O to 2 and

x + y + z = 4,

comprising:

A) the step of subjecting one or more methylhydndodisilanes of the general formula (II) Me_nSi₂H₆-n (II)

wherein n = 1 to 6, preferably n = 1 to 5,

to the cleavage reaction of the silicon-silicon bond, and

B) optionally a step of separating the resulting methylmonosilanes of the formula (I), wherein step A) is carried out by subjecting the methylhydndodisilanes of the general formula (II) to the reaction with hydrogen chloride (HCI) in the presence of one or more aprotic organic solvents.

(Aprotic organic solvents are usually solvents that do not have a functional group from which hydrogen atoms can be split off as protons (dissociation) under the process conditions as opposed to the protic solvents). Formula (II) MenSi₂H6-n can be depicted e.g. by a structural formula:

R' R'

\ /

R'— Si— Si— R'

/ \

R' R' wherein the R' substituents can be independently selected from methyl (Me) and hydrogen (H), with the proviso that there are 1 to 5 methyl substituents. Therein, "cleavage" is the term used to describe the process whereby disilanes are reacted to produce monomeric silanes. The term "cleavage reaction of the silicon-silicon bond" further indicates that according to the invention, the cleavage of the disilanes of the general formula (II) is effected by breaking the bond connecting the silicon atoms of the disilanes. Such cleavage processes include in particular hydrochlorination and hydrogenolysis.

It will be understood that any numerical range recited herein includes all sub-ranges within that range and any combination of the various endpoints of such ranges or sub-ranges, be it described in the examples or anywhere else in the specification.

It will also be understood herein that any of the components of the invention herein as they are described by any specific genus or species detailed in the examples section of the specification, can be used in one embodiment to define an alternative respective definition of any endpoint of a range elsewhere described in the specification with regard to that component, and can thus, in one non-limiting embodiment, be used to supplant such a range endpoint, elsewhere described. It will be further understood that any compound, material or substance which is expressly or implicitly disclosed in the specification and/or recited in a claim as belonging to a group of structurally, compositionally and/or functionally related compounds, materials or substances includes individual representatives of the group and all combinations thereof.

In the process of the present invention one compound of general formula (I) or a mixture of more than one compound of general formula (I) is formed. More preferably, mixtures of more than one compound of the formula (I) are formed.

Preferably, the methylmonosilanes of the general formula (I) formed in the process of the present invention include compounds selected from the group of: MeSihbCI, Me2SiH2, Me₂SiHCI, Me₃SiH, Me₃SiCI, MeSiHC , Me₂SiCI₂ and MeSiH₃.

Even more preferably, the methylmonosilanes of the general formula (I) formed in the process according to the invention include compounds selected from the group of Me2SiH2, Me₂SiHCI and MeSiH₂CI.

The one or more methyldisilanes subjected to the cleavage reaction of the silicon-silicon bond are represented by the general formula (II), wherein n = 1 to 5, preferably n = 2 to 5. Preferred starting materials of the general formula (II) include one or more of the compounds selected from MehbSi-SihbMe, Me₂HSi-SiH2Me, Me₂HSi-SiHMe2, Me₃Si-SiHMe2, Me₃Si- SiH₂Me, MeH₂Si-SiH₃, Me₂HSi-SiH₃ and mixtures thereof.

Particularly preferred starting materials of the general formula (II) comprise one or more of the compounds selected from MehbSi-SihbMe, Me2HSi-SiH2Me, Me2HSi-SiHMe2 and mixtures thereof. The present invention includes also the process wherein a substrate is reacted which comprises one or more methyldisilanes of the general formula (II), optionally in a mixture with other silanes not covered by general formula (I I) . The optional step of separating the resulting methylmonosilanes of the general formula (I) refers to any technical means applied to raise the content of one or several methylmonosilanes according to the general formula (I) in a product mixture, or which results in the separation of single compounds of the formula (I) from a product mixture obtained in step A) of the process according to the invention.

In a preferred embodiment of the process according to the invention, step A), i.e. subjecting one or more methyldisilanes of the general formula (I I) to the cleavage reaction of the silicon- silicon bond, is carried out by subjecting the methyldisilanes of the general formula (I I) to the reaction with hydrogen chloride (HCI) in the presence of an organic solvent, which is able to absorb or dissolve HCI and is able to cleave the Si-Si bond in the methyldisilanes in the presence of HCI.

In the sense of present invention, aprotic organic solvents are usually solvents that do not have a functional group from which hydrogen atoms can be split off as protons (dissociation) under the process conditions as opposed to the protic solvents. An aprotic organic solvent is any organic compound which is in liquid state at room temperature (about 23°C), and which is suitable as a medium for conducting the cleavage reactions therein. Accordingly, the aprotic organic solvent is preferably inert to hydrogen chloride under reaction conditions. Furthermore, the starting materials of the general formula (I I) and the products of the general formula (I) are preferably soluble in the organic solvent or fully miscible, respectively.

Furthermore, the term of "absorbing" or "absorption", each respectively, refers to the process of one material (absorbate), in this case hydrogen chloride, being retained by another (absorbent) , in this case the ether compound. The term of dissolving or dissolution, respectively, refers to the mixing of two phases with the formation of one new homogeneous phase, which in this case is a solution of hydrogen chloride in the ether compound.

In a further preferred embodiment of the process according to the invention, the aprotic organic solvent, which is present when step A) is carried out, is selected from one or more ether solvents.

In the present invention, the term "ether solvent" shall mean any organic compound containing an ether group -0-, in particular, of formula R₁-O-R₂, wherein Ri and R₂ are independently selected from a monovalent organyl group, which is bonded to oxygen via a carbon atom. Preferably, Ri and R₂ are substituted or unsubstituted linear or branched alkyl groups or aryl groups, which may have further heteroatoms such as oxygen, nitrogen, or sulfur. In the case of cyclic ether compounds, Ri and R2 can constitute together an optionally substituted alkylene or arylene group, which may have further heteroatoms such as oxygen, nitrogen, or sulfur.

The ether compounds can be symmetrical or asymmetrical with respect to the substituents at the ether group -0-. In a further preferred embodiment, the ether solvents according to the invention are selected from the group consisting of linear and cyclic ether compounds.

Herein, a linear ether compound is a compound containing an ether group R₁OR₂ as defined above, in which there is no connection between the Ri and R₂ group except the oxygen atom of the ether group, as for example in the symmetrical ethers Et20, n-Bu20, Ph20 or diisoamyl ether (/-Penty O), in which Ri = R₂, or in unsymmetrical ethers as t-BuOMe (methyl f-butyl ether, MTBE) or PhOMe (methyl phenyl ether, anisol).

A cyclic ether compound according to the invention is a compound in which one or more ether groups are included in a ring formed by a series of atoms, such as for instance 1 ,4- dioxane, which can be substituted e.g. by alkyl groups.

In a preferred embodiment, the ether compound is selected from the group consisting of diethyl ether, di-n-butyl ether, dioxane, preferably diethyl ether and di-n-butyl ether.

In a further preferred embodiment, the ether compound is selected from 1 ,4-dioxane, diethyl ether or di-n-butyl ether.

In another preferred embodiment of the process according to the invention, step A) is carried out with an ether solvent containing HCI in saturated and diluted solutions.

In the sense of the present invention, the term "saturated" refers to a saturated solution of hydrogen chloride in the ether compound applied, and is defined as a solution which has the same concentration of a solute as one that is in equilibrium with undissolved solute at specified values of the temperature and pressure. In the sense of present invention, a solution being close to the state of saturation is also comprised by the term "saturated". Such saturated solution can be prepared by passing gaseous hydrogen chloride into the corresponding ether compound (e.g. diethyl ether, di-n-butyl ether) at about 5 to about 10°C. The ether is saturated when excess HCI gas is evaporated over the overpressure valve as fast as it is introduced into the solvent. Diluted solutions are prepared stopping HCI- introduction into ethers before saturation or by dilution of saturated ether/HCI solutions with the corresponding pure ether solvent. Preferably, the HCI content of the ether solvent in the reaction step A) is > about 0.1 mol/l, more preferred > about 1.0 mol/l, even more preferred > about 3 mol/l, and most preferably the ether solvent is saturated with HCI as defined above.

Further preferably the HCI content of the ether solvent is > about 1 mol/l, even more preferred about 2 mol/l, and most preferably < about 3 mol/l, that is, in a preferred embodiment, the HCI content of the ether solvent is not "saturated".

In the context of this invention, it is also referred to Et₂0 used as solvent containing HCI as HCI/diethyl ether reagent, it is referred to di-n-butyl ether used as solvent containing HCI as HCI/di-n-butyl ether reagent, and it is referred to 1 ,4-dioxane used as solvent containing HCI as HCI/1 ,4-dioxane reagent.

Generally, increasing the HCI concentrations in ethers facilitates disilane chlorination SiH - SiCI which competes with disilane cleavage, while decreasing of the HCI concentrations facilitates disilane cleavage into SiH/SiCI substituted monosilanes, although longer reaction times are required. Furthermore, decreasing the reaction temperature facilitates disilane chlorination, while disilane cleavage reactions are preferred at elevated temperatures. The higher the degree of methylation at the backbone, the more disilane cleavage is favored, the higher the degree of hydrogenation, the higher the rate of chlorination, e.g. Me₂Si₂H4 is chlorinated to a greater extent than Me₄Si₂H2 under comparable conditions. As soon as a hydrogen substituent is replaced by chloride, subsequent disilane cleavage is inhibited. In case of the HCI/1 ,4-dioxane reagent chlorinated disilanes that are formed competitively to monosilanes from disilane cleavage, do not form siloxanes upon heating the samples. Reason for that is obviously the high stability of the cyclic ether against cleavage with HCI under moderate conditions.

In another preferred embodiment of the invention, step A) is carried out with diethyl ether saturated with HCI serving as the ether solvent saturated with HCI. Preferably, the saturation of the diethyl ether with hydrogen chloride is performed as described above, by passing gaseous hydrogen chloride into diethyl ether. In a preferred embodiment of the process according to the invention, during or after the cleavage reaction also a chlorination of methylhydridomonosilanes takes place.

Herein, the term "chlorination" refers to the replacement of one, two or three, preferably one or two Si-H bonds by Si-CI bonds. The methylhydridomonosilanes which are chlorinated during or after the cleavage reaction are methylmonosilanes of the general formula (I), wherein y is at least 1 , preferably 2 or 3.

By the chlorination as described above, methylmonochlorohydridomonosilanes which are methylmonosilanes of the general formula (I), wherein z is 1 or 2, are formed.

Preferably, MeSiH₃ is chlorinated to MeSiH₂CI, MeSiH₃ is dichlorinated to MeSiHC , Me₂SiH₂ is chlorinated to Me₂SiHCI and Me₃SiH is chlorinated to Me₃SiCI. In a further preferred embodiment according to the invention, step A) is conducted at a temperature of about 0 °C to about 140 °C, preferably about 20 to about 120 °C, more preferably about 60 °C to about 100 °C.

Herein, the reaction temperature in step A) according to the invention is the temperature of the reaction mixture, i.e. the temperature measured inside the reaction vessel in which the reaction is conducted.

Preferably, the reaction vessel can be an ampoule, a sealed tube, a flask or any kind of chemical reactor, without being limited thereto.

The cleavage of methylhydridodisilanes of the general formula (II) into methylchlorohydridomonosilanes and methylhydridomonosilanes, each of the general formula (I), already occurs at room temperature in Et₂0 in the presence of HCI. The chlorination reaction involving Si-H to Si-CI exchange in methylhydridomonosilanes to give methylmonochlorohydridomonosilanes and hydrogen gas formation also takes place. Increasing the reaction temperatures to about 50 - about 80 °C accelerates both reactions.

In another preferred embodiment of the process according to the invention, the step A) is conducted at a pressure of about 1 bar to about 30 bar, preferably about 1 bar to about 20 bar, most preferably about 1 bar to about 10 bar. The indicated pressure ranges refer to the pressure measured inside the reaction vessel used when conducting reaction step A).

In a preferred embodiment of the process according to the invention, in the step A) the molar ratio of the hydrogen chloride to the methylhydridodisilanes of the general formula (II) is at least about 1 :1 , more preferably in the range of about 1 : 1 to about 4:1.

Herein, the molar ratio is defined as n (HCI added to the mixture of reaction step A) / n (methylhydridodisilanes of the general formula (II) ).

For the determination of this ratio, all compounds being methylhydridodisilanes of the general formula (II) submitted to the reaction step (A) are considered, regardless if they are submitted in an isolated or pure form, or if they are part of a mixture comprising other compounds, in particular disilanes and carbodisilanes, which do not fall under the general formula (II).

In a further preferred embodiment of the process according to the invention, in the step A) the weight ratio of the methylhydridodisilanes of the general formula (II) to the organic solvent is less than about 1 :2, preferably in the range of about 1 :2 to about 1 :20.

Herein, the weight ratio is defined as m (methylhydridodisilanes of the general formula (II) ) / m (organic solvent).

For the determination of this ratio, all compounds being methyldisilanes of the general formula (II) submitted to the reaction step (A) are considered, regardless if they are submitted as a part of a mixture comprising other compounds, in particular disilanes and carbodisilanes, which do not fall under the general formula (II). Furthermore, the mass of any organic solvent according to above definition of the term "organic solvent" present in the reaction mixture submitted to reaction step (A) is considered in the determination of the weight ratio.

In another preferred embodiment of the process according to the invention, in the step A) the weight ratio of the hydrogen chloride to the organic solvent is less than about 1 :5, preferably in the range of about 1 :5 to about 1 :30. Herein, the weight ratio is defined as m (hydrogen chloride) / m (organic solvent). For the determination of this ratio, the mass of any organic solvent according to above definition of the term "organic solvent" present in the reaction mixture submitted to reaction step (A) is considered.

In a further preferred embodiment of the process according to the invention, the methylmonosilanes of the formula (I) are selected from the group consisting of Me2SiHCI, MeSihbCI, MeSiHC , Me₃SiCI, Me₃SiH, MeSih , Me₂SiCI₂ and Me₂SiH₂ and mixtures thereof.

In a particularly preferred embodiment of the process according to the invention, the methylmonosilanes of the formula (I) are selected from the group consisting of Me₂SiHCI, MeSiH₂CI, MeSiHCb, Me₂SiH₂ and MeSiH3 and mixtures thereof.

In a preferred embodiment of the process according to the invention, dimethylmonosilane Me₂SiH₂ is formed by submitting a substrate selected from the group consisting of Me₂HSi-SiHMe₂, Me₂HSi-SiH₂Me, Me₂HSi-SiH₃ or Me₂HSi-SiMe₃ to the cleavage reaction of the Si-Si bond.

Therein, each of the above-stated substrates may be submitted to the reaction conditions as single substrate, in a mixture with other compounds of the above-stated compounds, or in a mixture with other substrates of the general formula (II). In a further preferred embodiment of the process according to the invention, methylmonosilane MeSiH3 is formed by submitting a substrate selected from the group consisting of MeH₂Si-SiH₂Me, MeH₂Si-SiHMe₂, MeH₂Si-SiMe₃ or MeH₂Si-SiH₃ to the cleavage reaction of the Si-Si bond.

Therein, each of the above-stated substrates may be submitted to the reaction conditions as single substrate, in a mixture with other compounds of the above-stated compounds, or in a mixture with other substrates of the general formula (II).

In another preferred embodiment of the process according to the invention, dimethylchloromonosilane Me₂SiHCI is formed by submitting a substrate selected from the group consisting of Me₂HSi-SiHMe₂, Me₂HSi-SiH₂Me, Me₂HSi-SiH₃ or Me₂HSi-SiMe₃ to the cleavage reaction of the Si-Si bond. Therein, each of the above-stated substrates may be submitted to the reaction conditions as single substrate, in a mixture with other compounds of the above-stated compounds, or in a mixture with other substrates of the general formula (II). In a further preferred embodiment of the process according to the invention, methylchloromonosilane MeSiH₂CI is formed by submitting a substrate selected from the group consisting of MehbSi-SihbMe, MeH₂Si-SiHMe2, MehbSi-Sih or MeH₂Si-SiMe3 to the cleavage reaction of the Si-Si bond.

In another preferred embodiment of the process according to the invention, the step of separating the resulting methylmonosilanes of the formula (I) is carried out by distillation. The term "distillation" in the sense of the present invention relates to any process for separating components or substances from a liquid mixture by selective evaporation and condensation. Therein, distillation may result in practically complete separation, leading to the isolation of nearly pure components, or it may be a partial separation that increases the concentration of selected components of the mixture.

The distillation processes, which may constitute separation step B), can be simple distillation, fractional distillation, vacuum distillation, short path distillation or any other kind of distillation known to the skilled person. The step B) of separating the chlorosilanes of the formula (I) according to the invention can comprise one or more batch distillation steps, or can comprise a continuous distillation process.

In a further preferred embodiment of the process according to the invention, the methylhydridodisilanes of the general formula (II) are obtained by hydrogenation of the corresponding methylchlorodisilanes of the general formula (III)

MenSi₂CI₆-n (IN), wherein n is as defined above. Such methylchlorodisilanes are preferably residues from the Rochow-Muller Direct Process, and preferably contain mixtures of methylchlorodisilanes of formula (III).

In the present invention, the term "hydrogenation" is understood as substitution of one or more chloro substituents on the silicon atoms of the methylchlorodisilanes of the general formula (III) by one or more hydrogen atoms. Thus, the term "hydrogenation" refers to the transformation of one or more Si-CI bonds to one or more Si-H bonds.

Preferably, the starting material of the hydrogenation step of the general formula (I II) comprises one or more of the compounds selected from MeCI₂Si-SiCI₂Me, Me₂CISi- SiC Me, Me₂CISi-SiCIMe₂, Me₃Si-SiCIMe₂, Me₃Si-SiCI₂Me, MeC Si-SiC , Me₂CISi-SiCI₃ and mixtures thereof.

Particularly preferred starting materials of the general formula (III) comprise one or more of the compounds selected from MeCI₂Si-SiCI₂Me, Me₂CISi-SiCI₂Me, Me₂CISi-SiCIMe₂ and mixtures thereof.

The present invention includes also the case where substrates are subjected to hydrogenation which comprise one or more methylchlorodisilanes of the general formula (III) in admixture with other silanes not covered by general formula (I II).

In a further preferred embodiment of the invention, hydrogenation is carried out with a hydride donor, selected from the group of metal hydrides, preferably complex metal hydrides such as LiAIH₄, n-Bu₃SnH, NaBH₄, (;^'-Bu₂AIH)₂ or sodium bis(2- methoxyethoxy)aluminumhydride, which is commercially available under the trademarks Vitride® or Red-AI®, for instance.

In the sense of present invention, a hydride donor is any compound being capable of providing hydride anions for the transformation of methylchlorodisilanes of the formula (III) to methylhydridodisilanes of the formula (II).

In the sense of present invention, the term metal hydride refers to any hydride donor containing at least one metal atom or metal ion.

The term "complex metal hydrides" according to the invention refers to metal salts wherein the anions contain hydrides. Typically, complex metal hydrides contain more than one type of metal or metalloid. As there is neither a standard definition of a metalloid nor complete agreement on the elements appropriately classified as such, in the sense of present invention the term "metalloid" comprises the elements boron, silicon, germanium, arsenic, antimony, tellurium, carbon, aluminum, selenium, polonium, and astatine.

In another preferred embodiment, the methylchlorodisilanes of the general formula (III) which are subjected to hydrogenation are residues of the Rochow-Muller Direct Process (DPR). The primary commercial method to prepare alkylhalosilanes and arylhalosilanes is through the Rochow-Muller Direct Process (also called Direct Synthesis or Direct Reaction), in which copper-activated silicon is reacted with the corresponding organohalide, in particular methyl chloride, in a gas-solid or slurry-phase reactor. Gaseous products and unreacted organohalide, along with fine particulates, are continuously removed from the reactor. Hot effluent exiting from the reactor comprises a mixture of copper, metal halides, silicon, silicides, carbon, gaseous organohalide, organohalosilanes, organohalodisilanes, carbosilanes and hydrocarbons. Typically, this mixture is first subjected to gas-solid separation in cyclones and filters. Then the gaseous mixture and ultrafine solids are condensed in a settler or slurry tank from which the organohalide, organohalosilanes, hydrocarbons and a portion of organohalodisilanes and carbosilanes are evaporated and sent to fractional distillation to recover the organohalosilane monomers. The solids accumulated in the settler along with the less volatile silicon-containing compounds are purged periodically and sent to waste disposal or to secondary treatment. Organohalodisilanes and carbosilanes left in the post-distillation residues are also fed to hydrochlorination. Organohalodisilanes, organohalopolysilanes and carbosilanes, related siloxanes and hydrocarbons, either in the post-distillation residues or in the slurry purged from the reactor, boil above orgaohalosilane monomers. Collectively they are referred to as Direct Process Residue (DPR). The terms higher boilers, high-boiling residue and disilane fraction are also used interchangeably with DPR.

By the process according to the invention, methylchlorodisilanes of the general formula (I II) which are obtained as a constituent of the side-products of the Rochow-Muller Direct Process (DPR) can be transformed in particular to methylhydridosilanes of the general formula (I) via hydrogenation to methylhydridodisilanes of the general formula (II) and subsequent cleavage of the silicon-silicon bond as described.

According to the invention, the Direct Process Residue (DPR) utilized as starting material may comprise further silicon-based compounds which do not fall under general formula (III). In a further preferred embodiment, the process according to the invention is performed under inert conditions.

In the sense of present invention, the term "performed under inert conditions" means that the process is partially or completely carried out under the exclusion of surrounding air, in particular of moisture and oxygen. In order to exclude ambient air from the reaction mixture and the reaction products, closed reaction vessels, reduced pressure and/or inert gases, in particular nitrogen or argon, or combinations of such means may be used. Preferred embodiments of the invention:

In the following the preferred embodiments of the invention are shown:

1 . Process for the manufacture of methylmonosilanes of the general formula (I):

MexSiHyClz (I),

wherein

x = 1 to 3,

y = 0 to 3,

z = 0 to 2 and

x + y + z = 4,

comprising :

A) the step of subjecting one or more methyldisilanes of the general formula (I I)

Me_nSi₂H6i.-n (II)

wherein n = 1 to 6, preferably 1 to 5,

to the cleavage reaction of the silicon-silicon bond, and

B) optionally a step of separating the resulting methylmonosilanes of the formula (I) , wherein step A) is carried out by subjecting the methylhydndodisilanes of the general formula (II) to the reaction with hydrogen chloride (HCI) in the presence of one or more aprotic organic solvents.

(Aprotic organic solvents are usually solvents that do not have a functional group from which hydrogen atoms can be split off as protons (dissociation) under the process conditions as opposed to the protic solvents).

2. The process according to embodiment 1 , wherein said aprotic organic solvent(s) is/are able to absorb or dissolve HCI and is/are able to cleave Si-Si bonds in the presence of HCI.

3. The process according to embodiments 1 or 2, wherein said aprotic organic solvent is selected from one or more ether solvents.

4. The process according to embodiment 3, wherein said ether solvents are selected from the group consisting of linear and cyclic ether compounds.

5. The process according to embodiment 4, wherein the ether compound is selected from the group consisting of diethyl ether, di-n-butyl ether, dioxane, preferably diethyl ether and din-butyl ether.

6. The process according to any of the previous embodiments, wherein the ether compound is selected from 1 ,4-dioxane, diethyl ether or di-n-butyl ether. 7. The process according to any of the previous embodiments, wherein step A) is carried out with an ether solvent unsaturated or saturated with HCI, preferably an ether solvent saturated with HCI, preferably the ether solvent is diethylether.

8. The process according to the previous embodiments, wherein step A) is carried out with diethyl ether/HCI solutions of molarities in the range of about 0.5 to about 10 mol/L, preferably 1 to 6 mol/L (the solutions may have a temperature in the range of 0 to 25 °C).

9. The process according to any of the previous embodiments, wherein during or after the cleavage reaction also a chlorination of methylhydridomonosilanes takes place.

10. The process according to any of the previous embodiments, wherein the step A) is conducted at a temperature of about 0 °C to about 140 °C, preferably about 20 to about 120

°C, more preferably about 60 °C to about 100 °C.

1 1 . The process according to any of the previous embodiments, wherein the step A) is conducted at a pressure of about 1 bar to about 30 bar, preferably about 1 bar to about 20 bar, most preferably about 1 bar to about 10 bar.

12. The process according to any of the previous embodiments, wherein in the step A) the molar ratio of the hydrogen chloride to the methylhydridodisilanes of the general formula (II) is at least about 1 : 1 , more preferably in the range of about 1 : 1 to about 4: 1 .

13. The process according to any of the previous embodiments, wherein in the step A) the weight ratio of the methylhydridodisilanes of the general formula (II) to the organic solvent is less than about 1 :2, preferably in the range of about 1 :2 to about 1 :20.

14. The process according to any of the previous embodiments, wherein in the step A) the weight ratio of the hydrogen chloride to the aprotic organic solvent is less than about 1 :5, preferably in the range of about 1 :5 to about 1 :30.

15. The process according to any of the previous embodiments, wherein the methylmonosilanes of the formula (I) are selected from the group consisting of Me₂SiHCI,

MeSiH₂CI, MeSiHC , Me₃SiCI, Me₃SiH, MeSiH₃, Me₂SiCb and Me₂SiH₂.

16. The process according to any of the previous embodiments, wherein the methylmonosilanes of the formula (I) are selected from the group consisting of Me₂SiHCI, MeSiH₂CI, MeSiHCb, Me₂SiH₂ and MeSiH₃.

17. The process according to any of the previous embodiments, wherein dimethylmonosilane Me₂SiH₂ is formed by submitting a substrate selected from the group consisting of Me₂HSi-SiHMe₂, Me₂HSi-SiH₂Me, Me₂HSi-SiH₃ or Me₂HSi-SiMe₃ to the cleavage reaction of the Si-Si bond.

18. The process according to any of the embodiments 1 to 16, wherein methylmonosilane MeSiH₃ is formed by submitting a substrate selected from the group consisting of MeH₂Si-SiH₂Me, MeH₂Si-SiHMe2, MeH₂Si-SiMe₃ or MeH₂Si-SiH₃ to the cleavage reaction of the Si-Si bond.

19. The process according to any of the embodiments 1 to 16, wherein dimethylchloromonosilane Me₂SiHCI is formed by submitting a substrate selected from the group consisting of Me₂HSi-SiHMe₂, Me₂HSi-SiH₂Me, Me₂HSi-SiH₃ or Me₂HSi-SiMe₃ to the cleavage reaction of the Si-Si bond.

20. The process according to any of the embodiments 1 to 16, wherein methylchloromonosilane MeSiH₂CI is formed by submitting a substrate selected from the group consisting of MeH₂Si-SiH₂Me, MeH₂Si-SiHMe₂, MeH₂Si-SiH₃ or MeH₂Si-SiMe₃ to the cleavage reaction of the Si-Si bond.

21 . The process according to any of the previous embodiments, wherein the step of separating the resulting methylmonosilanes of the formula (I) is carried out by distillation.

22. The process according to any of the previous embodiments, wherein the methylhydridodisilanes of the general formula (I I) are obtained by hydrogenation of the corresponding methylchlorodisilanes of the general formula (II I)

Me_nSi₂CI₆-n (IN) ,

wherein n is as defined above.

23. The process according to the previous embodiments, wherein the hydrogenation is carried out with one or more hydride donors, selected from the group of metal hydrides, preferably complex metal hydrides such as LiAIH₄, n-Bu₃SnH, NaBH₄, (/^'-Bu₂AIH)₂ or sodium bis(2-methoxyethoxy)aluminumhydride.

24. The process according to any of the previous embodiments, wherein the methylchlorodisilanes of the general formula (I I I) are residues of the Rochow-Muller Direct Process (DPR) .

25. The process according to any of the previous embodiments, wherein the process is performed under inert conditions.

26. Methylmonosilanes of the general formula (I) as defined above, as obtainable by the process according to any of the previous embodiments.

27. Compositions comprising at least one methylmonosilane of the general formula (I) as defined above, as obtainable by the process according to any of the previous embodiments. EXAMPLES

The present invention is further illustrated by the following examples, without being limited thereto. General

To obtain the starting materials of the general formula (II), the methylchlorodisilanes of the general formula (III) MenSi₂Cl6-n (n=1 -5) were converted into their corresponding methylhydridodisilanes Me_nSi2H6-_n (n=1 -5) by hydrogenation with conventional hydrogenating reagents, such as complex metal hydrides (LiAIH₄, NaBH₄, ((/-Bu₂AIH)2 etc.) or mixtures thereof in ethers as solvents (e.g. diethyl ether, di-n-butyl ether, diglyme, 1 ,4-dioxane or mixtures thereof).

The methylhydridodisilanes of the general formula (II) were cleaved into the corresponding monosilanes of the general formula (I) by reaction with a HCI/ether solution (2-5 molar (= mol/l) in Et20, 1 -6 molar in n-Bu20). The complex reaction mixtures were analyzed by NMR- spectroscopy. The molar ratios of products formed were determined by integration of relevant NMR signals, which are assigned to specific products within the mixture.

The amount of products formed can be estimated by the molar ratios as measured by NMR spectroscopy and the amount of starting material applied (0.1 ml), assuming a density of 1 g/cm³ of the starting materials.

Preparation of HCI/ether solutions

Gaseous hydrogen chloride was slowly passed into the corresponding ether (diethyl ether, di-n-butyl ether, 1 ,4-dioxane) at about 5 to about 10°C. The ether was saturated when excess HCI gas was evaporating over the overpressure valve as fast as it was introduced into the solvent. Diluted solutions were prepared stopping HCI introduction into the ethers before saturation or by dilution of saturated ether/HCI solutions with the corresponding pure ether solvent. The molarity was 2-5 molar in Et20, and 1 -6 molar for HCI in in n-Bu20. The molarity of the HCI/ether reagent was determined by weighing the solutions: The obtained concentrations for saturated solutions were about 6 mol/l for HCI in di-n-butyl ether and about 5 mol/l for HCI in diethyl ether, and about 8-14 mol/l in 1 ,4-dioxane, depending on the amount of HCI introduced. The molarities of the HCI/ether solutions weighed were additionally confirmed by titration of HCI against sodium hydroxide (NaOH). General observations

The cleavage of methylhydridodisilanes into methylchlorohydridomonosilanes and methylhydridomonosilanes already starts at room temperature, and is accelerated at elevated temperatures and with increasing HCI concentrations in the ether solvents. In addition Si-H - Si-CI exchange in methylhydridomonosilanes to give methylmonochlorohydridomonosilanes and hydrogen gas was detected. Increasing the reaction temperatures from about 50 to about 80 °C accelerates both reactions. This is convincingly documented in the following tables. It should be noted that most cleavage and Si-CI - Si-H reduction experiments of disilane mixtures were performed with the HCI/diethyl ether reagent under optimum conditions for disilane cleavage (e.g. concentration of HCI ca. 2-3.5 mol/l; disilane chlorination (< 1 %) is omitted in the Tables), while pure disilanes were exemplarily reacted with the HCI/n-Bu₂0 reagent under concentration and temperature dependent reaction conditions. These experiments clearly demonstrate the strong influence of HCI concentrations in ethers and on reaction temperatures on the competitive formation of monosilanes and chlorinated disilanes. Generally, di-n-butyl ether decelerates cleavage and chlorination reaction compared to diethyl ether (~ 5 mol/l HCI each): For a comparison of product formation in different ethers as solvents for HCI it should be noted that cleavage/chlorination reactions have to be performed under strictly comparable conditions (HCI concentration and reaction temperature control)! Reaction times are given in the tables for complete consumption of disilanes and/or hydrogen chloride.

Identification of compounds

Products were analyzed by ¹H, ²⁹Si, ¹H-²⁹Si-HSQC and ¹H-²⁹Si-HMBC NMR spectroscopy. The spectra were recorded on a Bruker AV-500 spectrometer equipped with a Prodigy BBO 500 S1 probe. ¹H NMR spectra were calibrated to the residual solvent proton resonance ([D6]benzene 5H = 7.16 ppm). Product identification was additionally supported by GC-MS analyses and verified identification of the main products. GC-MS analyses were measured with a Thermo Scientific Trace GC Ultra coupled with an ITQ 900MS mass spectrometer. The stationary phase (Machery-Nagel PERMABOND Silane) had a length of 50 m with an inner diameter of 0.32 mm. 1 μΙ of analyte solution was injected, 1/25 thereof was transferred onto the column with a flow rate of 1 .7 mL/min carried by Helium gas. The temperature of the column was first kept at 50 °C for 10 minutes. Temperature was then elevated at a rate of 20 °C/min up to 250 °C and held at that temperature for another 40 minutes. After exiting the column, substances were ionized with 70 eV and cationic fragments were measured within a range of 34 - 600 m/z (mass per charge). Product mixtures were diluted with benzene prior to the measurement. The characteristic ²⁹Si-NMR chemical shifts and coupling constants J{²⁹Si-¹H} for compounds I to XXII are listed in Table 1.

Table 1

Example 1 :

(General procedure) Synthesis of methylhydridodisilanes from methylchlorodisilanes by the use of LiAlhU as hydroqenatinq reagent

LiAIH₄ (10% molar excess) was placed in a three neck flask and ether was added as solvent. Diethyl ether was used for high boiling methylhydridodisilanes of the general formula (II) and di-n-butyl ether, 1 ,4-dioxane or diglyme for low boiling disilanes of the general formula (II) to facilitate product separation by distillation at normal or reduced pressure. After cooling the ether/LiAIH₄ suspension to temperatures between -40 and 0 °C the methylchlorodisilane of the general formula (III) or a mixture comprising more than one methylchlorodisilane of the general formula (III) were added dropwise and slowly by a dropping funnel. After completion the resulting mixture was stirred for an additional hour at low temperature and then slowly warmed to r.t. and stirred for additional 12 hours to complete hydrogenation. The resulting methylhydridodisilanes of the general formula (II) were separated by condensation/distillation in vacuo and characterized NMR spectroscopically.

HCI/ether-cleavaqe of methylhydridodisilanes into the corresponding methylchlorohvdrido- and methylhydridomonosilanes

0.1 ml of a methylhydridodisilane of the general formula (II) or a mixture comprising more than one methylhydridodisilanes of the general formula (II) were dissolved in 0.1 ml C₆D₆ and placed in an NMR tube. After cooling to -196 °C (liquid nitrogen), 0.4 ml to 0.6 ml HCI/ether reagent were added, cooled (-196 °C), evacuated in vacuo and sealed. The cleavage reactions were performed in sealed NMR tubes to prevent evaporation of low boiling products and to control the cleavage reaction proceeding at different temperatures. After warming the sample to r.t. it was measured by NMR-spectroscopy and then reacted at different temperatures to control and quantify product formation (e.g. by integration of the intensity of relevant ²⁹Si-NMR signals within the product mixture).

Example 2:

A sample of methylhydridodisilanes I to III (0.1 ml) and V was reacted with the HCI/diethyl ether reagent (<5 molar, 0.4 ml) for 130 hours at 50 °C. As detected by NMR-spectroscopy 89% of the disilane MeH₂Si-SiH₂Me were already cleaved after 18 hours. About 50% of the resulting methylsilane (MeSiH₃) were already converted into monochlorinated MeSiH₂CI. After 130 hours nearly all disilanes were cleaved and methylsilane was transferred into methylchlorosilane in high yield (84%). In the same way Me2SiH2 (VIII) was slowly converted into Me₂Si(H)CI. Table 2 shows molar educt/product ratios at 50 °C with increasing reaction times. With increasing reaction times MeSiH₃ was slightly dichlorinated to give methyldichlorosilane XIV in small amounts.

Table 2

Example 3:

A mixture of the disilanes I to III (0.1 ml) was reacted with the HCI/di-n-butyl ether reagent (4.8 molar, 0.6 ml). As can be seen from Table 3 the resulting monosilanes are comparable to those formed with the HCI/diethyl ether reagent, but the reaction temperatures are higher, obviously the HCI/di-n-butyl ether reagent is less reactive than HCI/diethyl ether:

The molar ratio of products formed at 80 °C (17.5 h) and at 100 °C (97 h) is listed in Table 3 and demonstrates that the disilanes were converted into methylmonochlorohydrido- VII and methylhydridomonosilanes VI and VIII, that subsequently reacted to methylchlorohydridomonosilanes by chlorination with hydrogen chloride. Prolonged reaction times at higher temperatures finally lead to double chlorination of methylsilane VI to increasingly give MeSiHC XIV.

Table 3

Example 4:

A sample of methylhydridodisilanes II to V (0.1 ml), mainly consisting of disilane III (81 %), was reacted with the HCI/diethyl ether reagent (<5 molar, 0.4 ml) for 17 hours and then 105 hours at 50 °C. As detected by NMR spectroscopy all disilanes were completely cleaved into the corresponding monosilanes already after 17 hours. Comparing the molar product ratios demonstrates that after 105 hours reaction time dimethylsilane (Me₂SiH₂) was in part chlorinated into Me₂Si(H)CI (50% vs. 62%). The HCI/ether reagent is both a Si-Si-bond cleavage and a Si-H - Si-CI chlorinating reagent. The products formed and their molar ratio in the product mixture are listed in Table 4. Table 4

Example 5:

The cleavage reaction of the same disilane mixture of disilanes II to V (0.1 ml) as in example 4 with HCI/ether was performed in di-n-butyl ether (4.8 molar, 0.6 ml). As can be seen from Table 5 the resulting monosilanes are comparable to those formed with the HCI/diethyl ether reagent, but the reaction temperatures are higher (17 ½ hours at 80 °C and additional 97 hours at 100 °C). Prolonged reaction times at higher temperatures lead to mono and double chlorination of Me₂SiH₂ (VIII) to give preferably monochlorinated Me₂SiHCI (IX) and in small amounts Me2SiC (XV). The products formed and their molar ratios in the product mixture are listed in Table 5.

Table 5

Example 6:

A mixture consisting of methylhydridodisilanes I, II, IV and V and of monosilane VIII (5%) (0.1 ml) was reacted with the HCI/Et₂0 reagent (<5 molar, 0.4 ml) at 50 °C for 88 hours. Table 6 shows that all disilanes were cleaved into methylmonochlorohydridosilanes and methylhydridomonosilanes, whereby chlorination of methylhydridomonosilanes VI and VIII into the monochlorosilanes VII and IX becomes more and more significant with prolonged reaction times (Table 6). Table 6

Example 7:

A mixture of the methylhydndodisilanes I to I I I and V and the monosilanes VI and VI I I (0.1 ml) was reacted with the HCI/Et20 reagent (<5 molar, 0.4 ml) at 50 °C for 105 hours. Table 7 shows that all disilanes were already reacted into monosilanes after 17 hours giving mainly the chlorosilanes VI I and IX. The methylsilanes VI and VI I I were increasingly chlorinated by HCI/Et20 with increasing reaction time, finally giving compounds VI I in 38% and IX in 39% yield. With longer reaction times, the latter will be formed nearly quantitatively while VI I was already quantitatively formed from VI after 105 hours at 50 °C.

Table 7

Example 8:

A mixture of the methylhydndodisilanes I , I I I and V and the monosilane VI I I (0.1 ml) was reacted with the HCI/Et₂0 reagent (<5 molar, 0.4 ml) at 50 °C for 89 h. Table 8 shows that disilane cleavage is nearly quantitative giving mainly dimethylchlorosilane (IX, 64%). With prolonged reaction times, the yield of this compound is further increased by chlorination of dimethylsilane (VI I I) . Table 8

Example 9:

A complex sample of methylhydridodisilanes and the monosilanes listed in Tables 6, 7 and 8, consisting of a 1 :1 :1-mixture (0.05 ml each) of the mixtures from Examples 6, 7 and 8 was reacted with the HCI/Et₂0 reagent (<5 molar, 0.6 ml) at 50 °C for 41 hours. Then the reaction temperature was increased to 80 °C for additional 15 hours and then raised to 100 °C for 97 hours. In Table 9 products formed upon increased reaction temperatures and times are listed. All the disilanes, except highly methylated disilane V, were already transferred into monosilanes after 41 hours at 50 °C. At 100 °C even disilane V was completely transformed. Finally, the complete mixture gives the methylchlorosilanes VII and IX nearly quantitatively (44% vs. 46%). Together with the formation of trimethylsilanes X and XI the complete disilane mixture is transferred into valuable monosilanes quantitatively.

Notably, with prolonged reaction time the methylsilanes VI and VIII are increasingly chlorinated into VII and IX at 80 °C. At 100 °C this transfer is quantitative with simultaneous formation of disiloxane Me2HSi-0-SiHMe₂ (XIII) and chlorosilane XI. Example 10:

From examples 1 to 9 it is evident that HCI/Et₂0-cleavage of methylhydridodisilanes becomes more and more difficult with increasing degree of methylation at the disilane backbone using comparable HCI concentrations and reaction temperatures. For demonstration, pentamethyldisilane, Me₃Si-SiMe₂H (V) (0.1 ml) was reacted with the cleavage reagent (<5 molar, 0.4 ml) at different temperatures (50 and 80 °C). The products formed are listed in Table 10.

Table 10

Disilane V is nearly completely cleaved at 80 °C forming monosilanes IX and X. Obviously the cleavage product Me₂SiH₂ (VIII) is mostly chlorinated to give chlorosilane IX.

Example 11

Methylhydridodisilane III (0.08 ml, containing 3 μΙ diglyme) was separately reacted with the HCI/Et20 reagent (<5 molar, 0.5 ml) and the HCI/1 ,4-dioxane reagent (12 molar, 0.4 ml) for 18 h at 60 °C.

Table 11

Tetramethyldisilane III was completely cleaved with HCI/Et₂0 in the presence of a small amount of diglyme in the solution. HCI/1 ,4-dioxane both cleaves and substitutes the SiH- SiH-moiety.

Example 12

Cleavage reactions of dimethyldisilane I with the HCI//J-BU2O reagent with different molar HCI-concentrations and at different reaction temperatures. HO/nBuZO

Reactions: MeHrSi-SiHrMe— ♦ MeSiHs + MeSiH₂CI

BQ/nBuZO BO/nBu20

MeSiHs— * MeSiH₂CI— » MeSiHCb

The experimental results obtained are listed in Table 12.

Table 12

Comparing entries a) to d), e) to h) and i) to I) clearly proves that disilane cleavage is favored with comparable HCI concentrations with increasing reaction temperatures.

In the same way chlorination of hydridomonosilanes to give chlorinated products is supported, MeSiHs reacting faster do yield MeSiH₂CI, double chlorination to give MeSiHCh requires high HCI concentrations as well as high reaction temperatures. Noteworthy, the highest rate of disilane cleavage was obtained at 100 °C/5 d with a 2.5M HCI/n-Bu₂0 solution to give 54% of MeSiH₂CI and MeSiHCb (16.7%), while MeSiHs was detected in 7%. This is obviously due to the competitive Si-H - Si-CI chlorination of the monosilanes formed by predominant disilane cleavage.

Example 13:

Cleavage reactions of tetramethyldisilane III with the HCI/n-Bu₂0 reagent with different molar HCI-concentrations and at different reaction temperatures.

BO/nBu20

Reactions: Me₂HSi-SiHMe₂ » Me₂SiHCI + Me₂SiH₂

lCI niu20

Me₂SiH₂— » Me₂SiHCI

The experimental results obtained are listed in Table 13 and show comparable trends as obtained for disilane I (Table 12).

Table 13

Increasing reaction temperatures with low HCI-concentrations (entries a-d) yield the monosilanes Me₂SiHCI and Me₂SiH₂ quantitatively (d) with an increasing rate of monosilane chlorination of Me₂SiH₂ to give Me₂SiHCI. Chlorination of the disilane I I I occurs with high HCI concentrations at low temperatures (e.g. 41 % , entry i), increasing the temperature to 100 °C gives Me2SiHCI in 94% within one day, including nearly quantitative chlorination of Me₂SiH2 first formed by disilane cleavage.

Example 14:

Cleavage reactions of pentamethyldisilane V with the HCI/n-Bu₂0 reagent with different molar HCI-concentrations and at different reaction temperatures.

BCl/aBuZD

Reactions: Me₃Si-SiHMe2 Me₂SiHCI + Me₃SiH + Me₂SiH₂ + Me₃SiCI

lCI/niu20

Me₂SiH₂ Me₂SiHCI

BO/nBuZO

Me₃SiH MesSiCI

The cleavage of pentamethyldisilane V with the HCI/n-Bu₂0 reagent was exemplarily performed with a 2.5M HCI-concentration. The experimental findings are listed in Table 14.

Table 14

At lower reaction temperatures (r.t.) only chlorination to give disilane XI I was detected.

Disilane cleavage started at 40 ' C, the chloride of HCI binding to the Me₂SiH-moiety, while the hydrogen atom binds to the Me₃Si-unit. At 100 C the molar ratio Me₂SiHCI/Me₃SiH is nearly 1/1 (~ 42% each), cleavage was completed to give monosilanes quantitatively.

Example 15:

Cleavage reaction of hexamethyldisilane with the HCI/n-Bu₂0 reagent.

ΗΏ/nBuZO

Reactions: Me₃Si-SiMe3 > Me₃SiH + Me₃SiCI

BO/ni ZO

Me₃SiH » Me₃SiCI

As can be concluded from Table 15, disilane cleavage with 2.5M HCI//7-BU2O is quantitative within 4 days at 100 C to give the expected monosilanes. While the molar ratio is about 1/1 after 1 and 2 days, longer reaction times initiate chlorination of Me₃SiH - Me₃SiCI with excess HCI in the sample.

Table 15

Example 16:

Cleavage reactions of different disilanes with the HCI/1 ,4-dioxane reagent with different HCI-concentrations at different reaction temperatures.

The disilanes listed in Table 16 were reacted with 2.5M and 5.5M solutions of HCI in 1 ,4- dioxane at 80-140 C. The products obtained from disilane cleavage and competitive chlorination reactions are listed in Table 16. Table 16

As can be seen from entries a) and b) , increasing reaction temperatures supported disilane chlorination, the molar amount of monosilanes decreased from 74% to 36.5% with increasing T from 80 °C to 140 °C having the same HCI concentrations. Comparison of entries a) and c) show that an increase of the HCI concentration from 2.5M to 5.5M in 1 ,4-dioxane diminishes the amount of monosilanes from 74% to 61 %, formed at 80 °C. Reacting tetramethyldisilane I I I with a 2.5M HCI/1 ,4-dioxane solution at 80 °C and 140 °C gives excellent yields of Me2SiHCI by simultaneous cleavage of I I I and chlorination of Me2SiH2 with excess HCI. Notably, higher reaction temperatures shorten the reaction times. Higher HCI concentrations favor disilane chlorination (entry g). Pentamethyldisilane (V) is nearly quantitatively cleaved at 100 °C within 1 day to give the expected products. Example 17:

A sample of methyldisilanes I, I I , I I I , IV and V (0.1 ml) (molar composition see Table 17) was reacted with the HCI/n-Bu20 reagent (2.5M) at increasing reaction temperatures and with different reaction times. Products formed upon disilane cleavage/chlorination with subsequent monosilane chlorination are depicted in Table 18.

Table 17

Table 18

Optimum conditions for the formation of monosilanes were identified at T=80 °C for 10 days: Me₂SiHCI (31 %) , Me₂SiH₂ (13%), MeSiHCI₂ (8%), MeSiH₂CI (39%) formed predominantly, while chlorinated disilanes formed in about 5% . Interestingly, the molar amount of Me₂SiHCI (>39%) increased while that of MeSiH₂CI was decreased increasing the reaction temperature to 100 °C, but the competitive disilane chlorination was increased giving 10% of chlorinated derivatives.

While the above description contains many specifics, these specifics should not be construed as limitations on the scope of the invention, but merely as exemplifications of preferred embodiments thereof. Those skilled in the art may envision many other possible variations that are within the scope and spirit of the invention as defined by the claims appended hereto.

Example 18: A mixture of the highly methylated disilanes CIMe₂Si-SiMe₂CI (50%) , Me₃Si-SiMe₂CI (25%) and Me3Si-SiMe3 (25%) were mixed and reacted in n-Bu₂0 with LiH to give per hydrogenated methyldisilanes listed in Table 19.

Table 19

The per hydrogenated disilanes were then reacted with a 2.5M n-Bu₂0/HCI solution at 100°C for 3 days to give quantitative cleavage of the highly methylated disilanes to form the most valuable monosilanes Me₂SiHCI, Me₃SiH, and Me₃SiCI. Molar amounts of products formed are listed in Table 20. No oligomeric structures were detected ²⁹Si-NMR spectroscopically.

Table 20

Claims

1 Process for the manufacture of methylmonosilanes of the general formula (I): MexSiHyClz (I),

wherein

x = 1 to 3,

y = 0 to 3,

z = 0 to 2 and

x + y + z = 4,

comprising:

A) the step of subjecting one or more methyldisilanes of the general formula (II) Me_nSi₂H₆-n (II) wherein n = 1 to 6, preferably 1 to 5,

to the cleavage reaction of the silicon-silicon bond, and

2. The process according to claim 1 , wherein said aprotic organic solvent(s) is/are able to absorb or dissolve HCI and is/are able to cleave Si-Si bonds in the presence of HCI.

3. The process according to claims 1 or 2, wherein said aprotic organic solvent is selected from one or more ether solvents.

4. The process according to claim 3, wherein the ether compound is selected from the group consisting of diethyl ether, di-n-butyl ether, dioxane, preferably diethyl ether and di-n- butyl ether.

5. The process according to any of the previous claims, wherein step A) is carried out with an ether solvent unsaturated or saturated with HCI, preferably saturated with HCI.

6. The process according to any of the previous claims, wherein during or after the cleavage reaction also a chlorination of methylhydridomonosilanes takes place.

7. The process according to any of the previous claims, wherein the step A) is conducted at a temperature of about 0 °C to about 140 °C, preferably about 20 to about 120 °C, more preferably about 60 °C to about 100 °C.

8. The process according to any of the previous claims, wherein the step A) is conducted at a pressure of about 1 bar to about 30 bar, preferably about 1 bar to about 20 bar, most preferably about 1 bar to about 10 bar.

9. The process according to any of the previous claims, wherein in the step A) the molar ratio of the hydrogen chloride to the methylhydridodisilanes of the general formula (II) is at least about 1 : 1 , more preferably in the range of about 1 : 1 to about 4: 1 .

10. The process according to any of the previous claims, wherein in the step A) the weight ratio of the hydrogen chloride to the aprotic organic solvent is less than about 1 :5, preferably in the range of about 1 :5 to about 1 :30.

1 1 . The process according to any of the previous claims, wherein the methylmonosilanes of the formula (I) are selected from the group consisting of Me₂SiHCI, MeSiH₂CI, MeSiHC , MesSiCI, Me₃SiH, MeSihh, Me2SiCl2 and Me2SiH2, preferably the methylmonosilanes of the formula (I) are selected from the group consisting of Me₂SiHCI, MeSiH₂CI, MeSiHC , Me₂SiH₂ and MeSiH₃.

12. The process according to any of the previous claims, wherein dimethylmonosilane Me₂SiH₂ is formed by submitting a substrate selected from the group consisting of Me₂HSi-SiHMe₂, Me₂HSi-SiH₂Me, Me₂HSi-SiH₃ or Me₂HSi-SiMe₃ to the cleavage reaction of the Si-Si bond, or wherein methylmonosilane MeSiH₃ is formed by submitting a substrate selected from the group consisting of MehbSi-SihbMe, MeH₂Si-SiHMe₂, MeH₂Si-SiMe₃ or Meh Si-Sihh to the cleavage reaction of the Si-Si bond, or wherein dimethylchloromonosilane Me₂SiHCI is formed by submitting a substrate selected from the group consisting of Me₂HSi-SiHMe₂, Me₂HSi-SiH₂Me, Me₂HSi-SiH₃ or Me₂HSi-SiMe₃ to the cleavage reaction of the Si-Si bond, or wherein methylchloromonosilane MeSihbCI is formed by submitting a substrate selected from the group consisting of MehbSi-SihbMe, MeH₂Si- SiHMe₂, MeH₂Si-SiH₃ or MeH₂Si-SiMe₃ to the cleavage reaction of the Si-Si bond.

13. The process according to any of the previous claims, wherein the methylhydridodisilanes of the general formula (II) are obtained by hydrogenation of the corresponding methylchlorodisilanes of the general formula (II I)

MenSi₂CI₆-n (IN),

wherein n is as defined above.

14. The process according to the previous claim, wherein the hydrogenation is carried out with one or more hydride donors, selected from the group of metal hydrides, preferably complex metal hydrides such as LiAIH₄, n-Bu₃SnH, NaBH₄, (^'-Bu2AIH)2 or sodium bis(2- methoxyethoxy)aluminum hydride.

15. The process according to any of the previous claims, wherein the methylchlorodisilanes of the general formula (III) are residues of the Rochow-Muller Direct Process (DPR).