An Osmium-Carbene Complex with Fischer−Schrock Ambivalent Behavior

Complex Os(η 5 -C 5 H 5 )Cl(P i Pr 3 ) 2 ( 1 ) reacts with N 2 CHPh to give the carbene derivative Os(η 5 -C 5 H 5 )( CHPh)Cl(P i Pr 3 ) ( 2 ). Complex 2 affords the carbene-plus-organic fragment coupling products Os(η 5 -C 5 H 5 )(η 3 -CHPhC 6 H 5 )(P i Pr 3 ) ( 3 ), OsH(η 5 -C 5 H 5 )(CH 2 CHPh)(P i Pr 3 ), ( 4 ) and OsH(η 5 -C 5 H 5 ){η 2 -( E )-CHPh=CHCH CH 2 }(P i Pr 3 ) ( 5 ) by reaction with PhLi, MeLi, and CH 2 CHCH 2 MgCl, respectively. In solution, the phenyl groups of 3 exchange their positions. The fluxional process takes place via an alkyl intermediate, which can be trapped as Os(η 5 -C 5 H 5 )(CHPh 2 )(CO)(P i Pr 3 ) ( 6 ) under CO atmosphere. In toluene at 60 °C, complex 5 evolves into its allyl isomer Os(η 5 -C 5 H 5 ){η 3 -CH 2 CHCH(CH 2 Ph)}(P i Pr 3 ) ( 7 ). Complex 2 also reacts with HBF 4 and NaOCH 3 . The reaction with HBF 4 leads to [Os(η 5 -C 5 H 5 )(η 3 -CH 2 C 6 H 5 )Cl(P i Pr 3 )]BF 4 ( 8 ), which loses HCl to give the hydride-carbyne derivative [OsH(η 5 -C 5 H 5 )(⋮CPh)(P i Pr 3 )] + ( 9 ), while the reaction with NaOCH 3 affords the carbyne compound Os(η 5 -C 5 H 5 )(⋮CPh) (P i Pr 3 ) ( 10 ). In methanol as solvent, complex 10 evolves into the hydride-alkoxycarbene species OsH(η 5 -C 5 H 5 ){ C(OMe)Ph}(P i Pr 3 ) ( 11 ). The reaction of 10 with phenol in pentane leads to ( 12 ). The X-ray structures of 3, 5, 7, 9, and 12 are also reported.