A REMARKABLE DIFFERENCE IN THE REACTIVITY BETWEEN CIS-SILYLPLATINUM AND TRANS-SILYLPLATINUM COMPLEXES TOWARD INSERTION OF ACETYLENE

Reaction of cis-PtMe(SiPh(3))(PMe(2)Ph)(2) (1) with phenylacetylene in benzene readily proceeds at room temperature to give the acetylene-in sertion product cis-PtMe{C(Ph)=CH(SiPh(3))}-(PMe(2)Ph)(2), while trans -PtMe(SiPh(3))(PMe(2)Ph)(2) (2), which is the geometrical isomer of 1, is inactive toward acetylene-insertion. A mechanism of insertion invo lving a five-coordinate intermediate is proposed to account for the ma rked difference in the reactivity between the cis and trans isomers.