Reactions of alkynes with [Fe-2(CO)(6)(mu-PPh2){mu-eta(1):eta(2)(alpha,beta)-(H)C-alpha = C-beta = C gamma H-2}]: Formation of diphenylvinylphosphine-functionalized vinyl carbenes via carbon-carbon and carbon-phosphorus bondformation and hydrogen migration

Reaction of [Fe-2(CO)(6)(mu-PPh2){mu-eta(1):eta(alpha,beta-)(2)(H)C-alpha=C -beta=CgammaH2}] (1) with PhC=CPh results in allenyl-alkyne-phosphido coupl ing to give [Fe-2(CO)(6)(mu-PPh2){mu-eta(1)(P):eta(3)(C):eta(1)(C)-C(Ph)C(P h)C(H)C(=CH2)PPh2}] (2), bridged by a diphenylvinylphosphine-substituted vi nyl carbene. Under similar conditions 1 reacts with PhC=CMe to give an equa l mixture of the two possible regioisomers, [Fe-2(CO)(6)(mu-PPh2){mu-eta(1) (P):eta(3)(C):eta(1)(C)-C(Ph)C(Me)C(H)C(=CH2)PPH2}] (3a) and [Fe-2(CO)(6)(m u-PPh2){mu-eta(1)(P):eta(3)(C):eta(1)(C)-C(Me)C(Ph)C(H)C(=CH2)PPh2}] (3b). In contrast, 1 reacts with 2 equiv of PhC=CH to give the vinyl carbene brid ged [Fe-2(CO)(6)(mu-PPh2){mu-eta(1)(P):eta(3)(C):eta(1)(C)-(Ph)CCC(H)MeCH=C PhC(PPh2)}] (4), which results from a complex sequence of carbon-carbon and carbon-phosphorus bond formation and hydrogen migration steps.