MECHANISM OF ALKYNE REDUCTION BY THE HETEROBIMETALLIC DIHYDRIDE CP(CO)2RE(MU-H)PT(H)(PPH3)2

An account is presented of mechanistic studies of the reaction of the heterobimetallic dihydride CP(CO)2Re(mu-H)Pt(H)(PPh3)2 (9) With alkyne s which produces rhenium alkene complexes, CP(CO)2Re(alkene), and plat inum alkyne complexes, (alkyne)Pt(PPh3)2. Since the starting heterobim etallic dihydride is in equilibrium with trans-Cp(CO)2ReH2 (trans-7) a nd (alkyne)Pt(PPh3)2, the reaction constitutes an overall Pt(0) cataly zed reduction of alkynes by trans-7 to produce high yields of rhenium alkene complexes. The kinetics of the reaction help to establish the m echanistic steps leading to the rate determining formation of a reacti ve intermediate by dissociation of PPh3 from CP(CO)2Re(mu-H)Pt(H)(PPh3 )2 (9). Studies of reactions of vinyl platinum(II) compounds with CP(C O)2ReH- (17) are consistent with a proposed mechanism for steps follow ing the rate determining step.