Process for the manufacture of (iodoorganyl)alkoxysilanes

Process for the manufacture of an (iodoorganyl)alkoxysilane of the formula:

• ##STR9## in which R.sup.1 represents straight or branched chain alkylene having 1 to 20 carbon atoms, cycloalkylene having 5 to 8 carbon atoms or a unit of the type:
• ##STR10## wherein n is a number between 1 and 6 of methylene groups in the chain attached to the halogen and m is a number from 0 to 6, R.sup.2 represents alkoxy having 1 to 5 carbon atoms, methoxyethoxy or ethoxyethoxy, R.sup.3 and R.sup.4 may be the same or different and have the same meaning as R.sup.2 or represent branched or linear alkyl having 1 to 10 carbon atoms, phenyl or phenyl substituted with halogen, which process comprises reacting the corresponding chlorine or bromine silane compound with stoichiometric to double molar quantities of alkali, alkaline earth or ammonium iodide in the presence of 0.01 to 5 mol % of a quarternary ammonium, phosphonium, arsonium, antimonium or tertiary sulfonium salt with alkyl, aryl or aralkyl substitutents and an organic or inorganic anion or a crown ether, in an organic liquid or mixture of organic liquids which is substantially inert towards the silane and is able to dissolve at least partly the iodide or silane component.