Activation of 2-Propyn-1-ol Derivatives by Indenylruthenium(II) and -osmium(II) Complexes:  X-ray Crystal Structures of the Allenylidene Complexes [M(CCCPh₂)(η⁵-C₉H₇)(PPh₃)₂][PF₆]·CH₂Cl₂ (M = Ru, Os) and EHMO Calculations

Abstract

The allenylidene complexes [M( C C CR 2 )(η 5 -C 9 H 7 )L 2 ][PF 6 ] (M = Ru, L = PPh 3, L 2 = 1,2-bis(diphenylphosphino)ethane (dppe), bis(diphenylphosphino)methane (dppm), R 2 = 2 Ph ( 1a−c ), C 12 H 8 (2,2‘-biphenyldiyl) ( 2a−c ); M = Os, L = PPh 3, R 2 = 2Ph ( 3 ), C 12 H 8 ( 4 )) have been prepared by reaction of the complexes [MCl(η 5 -C 9 H 7 )L 2 ] with HC⋮CC(OH)R 2 and NaPF 6 in refluxing methanol. The crystal structures of [M( C C CPh 2 )(η 5 -C 9 H 7 )(PPh 3 ) 2 ][PF 6 ]·CH 2 Cl 2 (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 η 5 -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(η 5 -C 9 H 7 )L 2 ] (L = PPh 3, L 2 = dppe, dppm) with HC⋮CCMe(OH)Ph and NaPF 6 in refluxing methanol leads to the formation of the allenylidene complexes [Ru{ C C C(Me)Ph}(η 5 -C 9 H 7 )L 2 ][PF 6 ] ( 6a−c ) along with the vinylvinylidene isomers [Ru{ C C(H)C(Ph) CH 2 }(η 5 -C 9 H 7 )L 2 ][PF 6 ] (L = PPh 3 ( 5a ), L 2 = dppe ( 5b ), dppm ( 5c )). Only complex 6a could be isolated by chromatography (SiO 2 ) 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) CH 2 }(η 5 -C 9 H 7 )L 2 ] ( 7a−c ). The monosubstituted allenylidene complex [Ru{ C C C(H)Ph}(η 5 -C 9 H 7 )(PPh 3 ) 2 ][PF 6 ] ( 9 ) has been prepared by the reaction of [RuCl(η 5 -C 9 H 7 )(PPh 3 ) 2 ] with HC⋮CCH(OH)Ph and NaPF 6 in methanol. Under similar reaction conditions [RuCl(η 5 -C 9 H 7 )L 2 ] reacts with HC⋮CCH(OH)R and NaPF 6 to afford the alkenylmethoxycarbene derivatives [Ru{ C(OMe)C(H) CH(R)}(η 5 -C 9 H 7 )L 2 ][PF 6 ] (L 2 = dppe, R = Ph ( 11b ); L 2 = dppm, R = Ph ( 11c ), H ( 13 )). [RuCl(η 5 -C 9 H 7 )(PPh 3 ) 2 ] also reacts with HC⋮CC(OH)H 2 to give the hydroxyvinylidene complex [Ru{ C CH(CH 2 OH)}(η 5 -C 9 H 7 )(PPh 3 ) 2 ][PF 6 ] ( 12 ), which is stable toward the dehydration process.