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Abstract:
The reaction of the Pd(0) complexes (R-2'PC2H4PR2')Pd(C2H4) (R' = Pr-1, Bu-t) and ((Pr3P)-Pr-1)(2)Pd with SnR2 (R e.g. CH(SiMe3)(2)), Sn2Me6, and R3SnH (R = Me, Bu-n) has been studied, the latter representing tin in its oxidation states II-IV. Thereby, information was obtained on the mechanisms of four Pd-catalyzed reactions of organotin compounds, i.e., (a) the (2+2+1) cycloaddition of 2 ethyne and 1 stannylene to form a stannole, (b) the hydrogen elimination from trialkylstannanes to give hexaalkyldistannanes, (c) the hydrostannation of alkynes to afford vinylstannanes, and (d) the jive of alkynes to yield distannylalkenes. All reactions are likely to involve intermediates having Pd-Sn bonds, although for (d) the occurrence of a previously suggested L2Pd(SnMe3)(2) intermediate in the catalytic cycle has en ruled out.
