Method for hydrogenating higher halogen-containing silane compounds

1. A continuous process for hydrogenating halogen-containing silane compounds having at least three silicon atoms, comprising:

(i) continuously converting

at least one halogen-containing silane compound having at least three silicon atoms and at least one hydrogenating agent

to form

at least one hydridosilane compound having at least 3 silicon atoms and an oxidized hydrogenating agent;

(ii) withdrawing and reducing the oxidized hydrogenating agent, and

(iii) feeding back the reduced oxidized hydrogenating agent to (i).

2. The process according to claim 1 , wherein the halogen-containing silane compound has the generic formula Si n X 2n+2 where 3≦n≦10 and X═F, Cl, Br, and/or I.

3. The process according to claim 2 , characterized in that wherein the halogen-containing silane compound is Si 5 Cl 12 .

4. The process according to claim 1 , wherein the proportion of the at least one halogen-containing silane compound ranges from 10-30% by weight based on the total mass of the components fed in.

5. The process according to claim 1 , wherein the hydrogenating agent is selected from the group of compounds consisting of LiAlH 4 , NaBH 4 and i-Bu 2 AlH.

6. The process according to claim 1 , wherein the hydrogenating agent in the reduced state is metered in H equivalent proportions of 1.0 to 1.5 based on the sum total of halogen atoms to be hydrogenated.

7. The process according to claim 1 , wherein at least two series-connected reactors are used for the conversion.

8. The process according to claim 7 , wherein the molar ratio in the first reactor of reduced to oxidized hydrogenating agent ranges from 0.4 to 0.75.

9. The process according to claim 7 , wherein the first of the two or more series-connected reactors is a stirred tank reactor.

10. The process according to claim 7 , wherein at least one of the reactors connected downstream of the first reactor is a flow reactor.

11. The process according to claim 1 characterized in that it that follows on from a process for synthesizing halogenated silane compounds in which

i) at least one halosilane of the generic formula Si n X 2n+2 where n≧2 and X═F, Cl, Br and/or I and

ii) at least one catalyst selected from the group of the tertiary phosphines PR 3 , the tertiary amines NR 3 and the group of compounds of the generic formula NRR′ a R″ b Y c

where a=0 or 1, b=0 or 1, and c=0 or 1, and

where

aa) R, R′ and/or R″ is —C 1 -C 12 -alkyl, —C 1 -C 12 -aryl, —C 1 -C 12 -aralkyl, —C 1 -C 12 -aminoalkyl, —C 1 -C 12 -aminoaryl, —C 1 -C 12 -aminoaralkyl,

and/or

two or three R, R′ and R″ radicals, in the case that c=0, together form a cyclic or bicyclic, heteroaliphatic or heteroaromatic system including N,

with the proviso that at least one R, R′ or R″ radical is not —CH 3

and/or

bb) R and R′ and/or R″ (in the case that c=1) are —C 1 -C 12 -alkylene, —C 1 -C 12 -arylene, —C 1 -C 12 -aralkylene, —C 1 -C 12 -heteroalkylene, —C 1 -C 12 -heteroarylene, —C 1 -C 12 -heteroaralkylene and/or —N═, or

cc) (in the case that a=b=c=0) R═≡C—R′″ (where R′″═—C 1 -C 10 -alkyl, —C 1 -C 10 -aryl and/or —C 1 -C 10 -aralkyl),

are converted to form a mixture comprising at least one halosilane of the generic formula Si m X 2m+2 (where m>n and X═F, Cl, Br and/or I) and Si m−n X 2(m−n)+2 (where X═F, Cl, Br and/or I).