Reaction of the anionic vinylidene complex K[Tp'(CO)(2)M=C=CH2] (M = Mo, W; Tp' = hydridotris(3,5-dimethylpyrazolyl)borate) with Tp(CO)(PhC=CPh)W-I (Tp = hydridotris(pyrazolyl)borate) yields Tp'(Co)(2)MCCH2-W(Co)(PhC=CPh)Tp (M = Mo, 4; W, 5) and potassium iodide. Removal of a methylene proton from the (=CCH2-) bridge with KOBut forms a monoanion containing a putative carbene moiety. Oxidation of the anion with iodine leads to net hydride removal and yields the unusual C-2-bridged dimers Tp'(Co)(2)M=CC=W(CO)(PhC=CPh)Tp (M = Mo, 7; W, 8). Conversion of the tungsten-carbon single bond in the precursor complex to a triple bond in the product is accompanied by a significant reduction in donation to the metal from the alkyne pi(perpendicular to) orbital.