Deprotonation and Oxidation of the W⋮CCH2−W Bridge To Form a C2-Biscarbyne W⋮C−C⋮W Bridge

Reaction of the anionic vinylidene complex K[Tp‘(CO) 2 M C CH 2 ] (M = Mo, W; Tp‘ = hydridotris(3,5-dimethylpyrazolyl)borate) with Tp(CO)(PhC⋮CPh)W−I (Tp = hydridotris(pyrazolyl)borate) yields Tp‘(CO) 2 MCCH 2 −W(CO)(PhC⋮CPh)Tp (M = Mo, 4; W, 5 ) and potassium iodide. Removal of a methylene proton from the (⋮CCH 2 −) bridge with KOBu t 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 π ⊥ orbital.