Method for preparing di-organo-dialkoxysilanes

A method for preparing a di-organo-di-alkoxysilane compound comprising:

• a) reacting a tetraalkoxysilane compound having the general formula Si(OR1)4 with a first Grignard reagent of general formula R2—Mg—X, to form a mono-organo-tri-alkoxysilane compound of general formula R2—Si(−OR1)3, wherein the molar ratio of the first Grignard compound and the tetraalkoxysilane compound is from 1 to 1.5;
• b) reacting the mono-organo-tri-alkoxysilane compound of step a) with a chlorinating agent to form a chlorinated mono-organo-di-alkoxysilane compound of general formula,
• wherein the molar ratio between the mono-organo-tri-alkoxysilane compound to the chlorinating agent is from 1 to 1.5;
• c) reacting the chlorinated mono-organo-di-alkoxysilane compound of step b) with a second Grignard reagent of general formula R3—Mg—X to form the di-organo-di-alkoxysilane compound of general formula,
• wherein molar ratio of the second Grignard compound and the chlorinated mono-substituted dialkoxy silane compound is from 1 to 1.5;
• and
• wherein R1, R2 and R3 are independently selected from an alkyl group having 1 to 20 carbon atoms, and a cycloalkyl group having 3 to 20 carbon atoms, optionally containing a heteroatom;
• and wherein X is iodine, bromine or chlorine.