1536051 Ketoximino silanes; organopolysiloxane compositions GENERAL ELECTRIC CO 11 March 1976 09826/76 Headings C3S and C3T A silane having the general formula wherein R is a hydrocarbyl, halohydrocarbyl, nitrohydrocarbyl, alkoxyhydrocarbyl polyalkoxyhydrocarbyl, diphenoxyphenyl or cyanoalkyl radical having not more than 8 carbon atoms excluding any substituents, R<SP>1</SP> and R<SP>2</SP> are C 1 -C 8 alkyl or haloalkyl radicals, R<SP>3</SP> is a divalent radical having from 2-8 carbon atoms selected from saturated hydrocarbon, halohydrocarbon, nitro-substituted hydrocarbon and alkoxy-substituted hydrocarbon radicals, R<SP>6</SP> is the same as R, a is 1-3, d is 1-3, f is 0-2 and the sum of a, d and f is 4, are prepared by first reacting a silane of the formula (H) d (X) a Si(R<SP>6</SP>) f with an ester of the formula RCOOR<SP>7</SP>, where R<SP>7</SP> is a C 2 -C 7 olefinically unsaturated hydrocarbon radical optionally substituted by halo, nitro, or alkoxy groups, and X is halogen, in the presence of a Pt compound or complex, via a SiH-olefin addition reaction, and reacting the product with a ketoxime of the formula R<SP>1</SP>R<SP>2</SP>C=NOH in the presence of a tertiary amine and optionally a solvent. The silanes can be used as crosslinking agents, chain-extending agents and chain-terminating agents depending on whether a in the formula of the silane is 3, 2 or 1, respectively, in the preparation of RTV fluid compositions stable under anhydrous conditions and curable to an elastic solid in the presence of moisture, comprising a silanol-terminated polydiorganosiloxane of the formula wherein R<SP>4</SP> and R<SP>6</SP> are hydrocarbyl, halohydrocarbyl or cyanoalkyl radicals having not more than 8 carbon atoms and n is 10 to 15,000, the polydiorganosiloxane preferably having a viscosity of from 100 to 120,000 cP at 25‹ C. Preferably at least 50% of the R<SP>4</SP> and R<SP>6</SP> radicals are methyl, the remainder, if any, being phenyl. The polydiorganosiloxane can contain some t-alkoxy groups, e.g. t-butoxy groups. The RTV compositions optionally comprise an inert organic solvent; a catalyst which is a carboxylic acid salt and/or a carboxylic acid chelate of a metal ranging from Pb to Mn, in the electromotive series of metals, e.g. dibutyltin dilaurate or basic dimethyltin oleate; fillers, e.g. titanium dioxide, lithopone, zinc oxide, zirconium silicate, silica aerogel, iron oxide, calcium carbonate, diatomaceous earth, fumed silica, silazane treated silica, precipitated silica, glass fibres, MgO, chromic oxide, zirconium oxide, aluminium oxide, crushed quartz, clay, asbestos, carbon, graphite, cork, cotton and synthetic fibres; flame retardants, e.g. antimony oxide, polychlorinated hydrocarbons and organic sulphonates; stabilizers and plasticizers, e.g. siloxane fluids; and adhesion promoters, e.g. 1,3,5-gamma tris-trimethoxysilylpropylisocyanurate. In Example 1 tris-(methylethylketoximino)silylethyl acetate is prepared by reacting methylethylketoxime with acetoxyethyltrichlorosilane in the presence of anhydrous diethyl ether and triethyl amine. In Examples 2-4 RTV compositions are prepared from the following formulations: the silane of Example 1, basic dimethyltin oleate or dibutyltin dilaurate, a silanol-terminated polydimethylsiloxane fluid (3000-7000 cP), and either (1) octamethylcyclotetrasiloxanetreated fumed silica of surface area 200 m.<SP>2</SP>/g., TiO 2 , an OH-containing polysiloxane process aid consisting of monomethylsiloxy, dimethylsiloxy and trimethylsiloxy units and optionally a thixotrope consisting of a trimethylsilyl terminated oil composed of diphenylsiloxy and dimethylsiloxy units; or (2) a hexamethyldisilazane treated fumed silica. Uses.-Caulking and sealing.