Three series of substituted 1,3,4-oxadiazoles were studied by (17)O NMR spectroscopy. Chemical shifts values were correlated with empirical Hammett parameters as well as calculated bond lengths and chemical shielding values.

The ruthenium hydride complex-catalyzed N-silylation of primary and secondary amines with substituted vinylsilanes, with the general formula R(1)CH=CHSiR (where R(1) = H, Ph, n-Bu, Si(OEt)3), leading to the formation of a Si-N bond with the evolution of olefin is described. Vinylsilane acts as a silylative reagent and hydrogen acceptor. Under optimum conditions, the reaction offers an attractive route for the synthesis of silylamines. The preliminary mechanistic view of this novel general silylation reaction based on catalytic and deuterium labeling experiments, using NMR and GC-MS methods, confirm the synthetic observations.

The regioselectivity of metathesis reactions of trisubstituted vinylsilanes H 2 CCHSiR 3 (SiR 3 = SiCl 3 , SiCl 2 Me, SiClMe 2 , SiMe 3 , Si(OEt) 3 ) with the second-generation ruthenium alkylidene complex has been studied theoretically, by density functional theory (DFT), and experimentally. The DFT results indicate that cycloreversion is the rate-determining step and the formation of a thermodynamically stable ruthenium methylidene complex and PhCHCHSiR 3 is generally preferred. However, the regioselectivity of the process can be also governed by the relative stabilities of the ruthenacyclobutane intermediates, which depend on the electronic and steric properties of the SiR 3 substituent. Higher stability of α,β-disubstituted ruthenacyclobutanes in comparison to α,α-disubstituted ruthenacyclobutanes is predicted, in contrast to the corresponding intermediates formed during metathesis of common α-olefins. The stabilizing Ru−C β interaction in the ring is strengthened by the electron-donor SiR 3 substituent at C β . The experiments performed have shown selectivity toward styrene formation for SiR 3 = SiClMe 2 , SiMe 3 , whereas a preference for the formation of ruthenium methylidene and PhCHCHSiR 3 has been observed for SiR 3 = SiCl 3 , SiCl 2 Me, Si(OEt) 3 , in accordance with the theoretical predictions.

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