Photoinduced Carbonylation of the Carbyne Ligand in (η-C₅H₅)(CO)₂W≡CTol

UV irradiation of solutions of Cp(CO)₂W≡CTol (1) (Tol = p-C₆H₄CH₃; Cp = η-C5H5) in the presence of CO induces carbonylation of the carbyne ligand and formation of the binuclear complex [Cp-(CO)₂W]₂(η-Tolcc{O}Ctol)(2). Complex 2 has been crystallographically characterized: triclinic, P1, a = 8.773 (2) Å, b = 12.042 (3) Å, c = 14.866 (5) Å,α = 91.81 (2)°, β = 94.12 (2)°, γ = 110.32 (2)°, R_F = 4.63%, R_wF = 5.62% for 3075 reflections with F_o≥ 3σ(F_o). The bridging ligand of 2 consists of two carbyne units linked by a CO with the latter not bonded to either metal. Irradiation of 1 in the presence of PPh₃ leads to rapid formation of the known ketenyl complex Cp(CO)(PPh₃)W(η²-TolCCO) (5). Complex 5 reacts further with CO to form the η¹-ketenyl species Cp(CO)₂(PPh₃)W(η¹-TolCCO). Photolysis of 1 in the presence of dppe (dppe = 1,2-bis(diphenylphosphino)ethane) yields the η¹-ketenyl species Cp(CO)(dppe)W(η¹-TolCCO), which readily loses dppe to give the novel binuclear η²-ketenyl derivative [Cp(CO)W(η²-TolCCO)]₂(μ-dppe).