Ruthenium Cluster Chemistry with Ph₂PC₆H₄-4-C = CH

The new phosphines Ph₂PC₆H₄-4-C = CR [R = SiMe₃ (1), H (2)] have been used to prepare Ru₃(CO)₉(Ph₂PC₆H₄-4-C = CSiMe₃)₃ (4) and Ru(C = CC₆H₄-4-PPh₂)(PPh₃) ₂(η-C₅H₅) (3), respectively, the latter with a pendent phosphine. Reaction of 4 with carbonate or fluoride affords Ru₃(CO)₉(Ph₂PC₆H₄-4-C = CH)₃ (5) with pendent terminal alkynyl groups, the identity of which was confirmed by a structural study. Reaction of 5 with [Ru(NCMe)(PPh₃)₂(η-C₅H₅)]PF ₆ or reaction of Ru₃(CO)₁₂ with 3 gives Ru₃(CO)₉{(Ph₂PC₆H₄-4-C = C)Ru(PPh₃)₂(η-C₅H₅)}₃ (6). Complexes 3-6 have been studied by cyclic voltammetry. Proceeding from Ru₃(CO)₁₂ to 4 or 5 shifts the cluster-centred reduction to more negative potential and affords facile cluster-centred oxidation. Proceeding from 4/5 and 3 to 6 results in similarly-located cluster-centred reduction and peripheral ruthenium-centred oxidation, but results in a lack of observable cluster-centred oxidation. Crystal data for 5·C₆H₁₄: space group P1, a = 12.760(1) Å, b = 17.077(1) Å, c = 17.924(2) Å, α = 108.656(5)°, β = 96.344(5)°, γ = 93.523(5)°, V = 3658.4(6) ų, Z = 2, R = 0.078, R_w = 0.105 for 5008 reflections [I > 2.00σ(I)].