Activation of 2-Propyn-1-ol Derivatives by Indenylruthenium(II) and -osmium(II) Complexes:  X-ray Crystal Structures of the Allenylidene Complexes [M(CCCPh₂)(η⁵-C₉H₇)(PPh₃)₂][PF₆]·CH₂Cl₂ (M = Ru, Os) and EHMO Calculations

The allenylidene complexes [M(CCCR₂)(η⁵-C₉H₇)L₂][PF₆] (M = Ru, L = PPh₃, L₂ = 1,2-bis(diphenylphosphino)ethane (dppe), bis(diphenylphosphino)methane (dppm), R₂ = 2 Ph (1a−c), C₁₂H₈ (2,2‘-biphenyldiyl) (2a−c); M = Os, L = PPh₃, R₂ = 2Ph (3), C₁₂H₈ (4)) have been prepared by reaction of the complexes [MCl(η⁵-C₉H₇)L₂] with HC⋮CC(OH)R₂ and NaPF₆ in refluxing methanol. The crystal structures of [M(CCCPh₂)(η⁵-C₉H₇)(PPh₃)₂][PF₆]·CH₂Cl₂ (M = Ru (1a), Os (3)) were determined by X-ray diffraction methods. In the structures the MCCC chains are nearly linear (M−C(1)−C(2) = 168.5(5)° (1a) and 169.3(4)° (3); C(1)−C(2)−C(3) = 168.2(7)° (1a) and 168.0(5)° (3)) with MC(1) distances of 1.878(5) Å (1a) and 1.895(4) Å (3). The indenyl ligand is η⁵-bonded to the metal with the benzo ring orientated “cis” with respect to the allenylidene group. Extended Hückel molecular orbital calculations have been used to rationalize the preferred “cis” orientation. The reaction of [RuCl(η⁵-C₉H₇)L₂] (L = PPh₃, L₂ = dppe, dppm) with HC⋮CCMe(OH)Ph and NaPF₆ in refluxing methanol leads to the formation of the allenylidene complexes [Ru{CCC(Me)Ph}(η⁵-C₉H₇)L₂][PF₆] (6a−c) along with the vinylvinylidene isomers [Ru{CC(H)C(Ph)CH₂}(η⁵-C₉H₇)L₂][PF₆] (L = PPh₃ (5a), L₂ = dppe (5b), dppm (5c)). Only complex 6a could be isolated by chromatography (SiO₂) from these mixtures along with complex 7a obtained from the deprotonation of the vinylvinylidene complex 5a. The treatment of these reaction mixtures with potassium carbonate yields the neutral σ-enynyl derivatives [Ru{C⋮CC(Ph)CH₂}(η⁵-C₉H₇)L₂] (7a−c). The monosubstituted allenylidene complex [Ru{CCC(H)Ph}(η⁵-C₉H₇)(PPh₃)₂][PF₆] (9) has been prepared by the reaction of [RuCl(η⁵-C₉H₇)(PPh₃)₂] with HC⋮CCH(OH)Ph and NaPF₆ in methanol. Under similar reaction conditions [RuCl(η⁵-C₉H₇)L₂] reacts with HC⋮CCH(OH)R and NaPF₆ to afford the alkenylmethoxycarbene derivatives [Ru{C(OMe)C(H)CH(R)}(η⁵-C₉H₇)L₂][PF₆] (L₂ = dppe, R = Ph (11b); L₂ = dppm, R = Ph (11c), H (13)). [RuCl(η⁵-C₉H₇)(PPh₃)₂] also reacts with HC⋮CC(OH)H₂ to give the hydroxyvinylidene complex [Ru{CCH(CH₂OH)}(η⁵-C₉H₇)(PPh₃)₂][PF₆] (12), which is stable toward the dehydration process.