New Access to Vinylidenes from Ruthenium Polyhydrides

Reaction of the terminal acetylenes RC⋮CH (R = Ph and SiMe 3 ) with RuH 3 XL 2 (X = Cl, I; L = P t Bu 2 Me) occurs (in the time of mixing) in a 2:1 stoichiometry to release RHC CH 2 and form the vinylidene complexes RuHX(CCHR)L 2 . Ab initio DFT (B3LYP) calculations show that the vinylidene complex has a Y structure with a Cl at the foot of the Y. No intermediate is seen for this reaction, even at low temperature, or for the analogous reaction of OsH 3 Cl(P i Pr 3 ) 2 . Since PhC⋮CD forms only the isotopomer RuDI(CCHPh)L 2 and PhHC CHD, a mechanism is proposed where an early event is addition of Ru−H across the C⋮C bond. Preliminary computational studies of the reaction path for the formation of the vinylidene complex support this step of insertion of the acetylene into the Ru−H bond.