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The kinetics of substrate conversions in the commercially important hydrosilylation of allyl chloride with trichlorosilane, catalyzed by active carbon-supported platinum, as well as the yields of the main product (3-chloropropyltrichlorosilane) and by-products (tetrachlorosilane, propyltrichlorosilane) have been studied. On the basis of the measurements performed, the pseudo first-order rate constants (k obs , k 1 and k 2 from the model of competitive reactions) and activation energy (E a = 11 kcal mol À1 (46.2 kJ mol À1 )) were determined. The data obtained point to a non-linear dependence of k obs on the catalyst amount. From the kinetic relationships, the kinetic equation was deduced. All the results of kinetic, IR spectroscopic and thermogravimetric measurements, as well as the derived kinetic equation, have confirmed the general model of consecutive±competitive reaction involving the formation of a surface complex C 1 which can decompose in two directions according to the Chalk±Harrod mechanism.

Trisubstituted silanes, HSiR 3_.X n (R = Me, Et, Pr or Bu; X --C1, OEt or Ph; and n = 0-3) readily undergo oxidative addition to complex [RhCl(cod)PPh3] (where cod = cycloocta-1,5-diene).The quantitative correlation between rate constants, kl, of the reaction, followed spectrophotometrically at 20~ in benzene solutions, and the structure of trisubstituted silanes represented by stereoelectronic parameters Z, 0 and E" of the substituents, was established: log kl = a + b)~ + cO + dE". The reaction rate is accelerated by electron-withdrawing substituents at silicon and retarded by the bulk and p~d~ donation of nonalkyl substituents.

Trisubstituted silanes, HSiR 3 _,X, (R = Me or Et, X = C1, OEt, or Ph; n =0-3) oxidatively add to the complex [RhCl(cod)(1-hexene)](cod =cycloocta-l,5-diene) to yield [RhCl(cod)(1-hexene)(H)(SiR3)] [-(I )]. Subsequent steps of hydrosilylation follow, i.e. cis-insertion of the alkene (u-a rearrangement) and then reductive elimination of the product, according to the general Chalk and Harrod scheme. A quantitative correlation between the second order rate constant, kl, of the oxidative addition (followed spectrophotometrically) at 20 ~ in benzene solution and the structure of the trisubstituted silane represented by stereoelectronic parameters Z, 0 and E" for the SiR3_,X . groups was established. The maximal hydrosilylation rate followed by g.l.c., is strongly retarded by highly electronegative substituents X on silicon and results from the elimination rate of the hydrosilylation product from (1) and the maximal concentration of (1) in solution.

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