An Osmium-Carbene Complex with Fischer−Schrock Ambivalent Behavior

Abstract

Complex Os(η5-C5H5)Cl(PiPr3)2 (1) reacts with N2CHPh to give the carbene derivative Os(η5-C5H5)(CHPh)Cl(PiPr3) (2). Complex 2 affords the carbene-plus-organic fragment coupling products Os(η5-C5H5)(η3-CHPhC6H5)(PiPr3) (3), OsH(η5-C5H5)(CH2CHPh)(PiPr3), (4) and OsH(η5-C5H5){η2-(E)-CHPh=CHCHCH2}(PiPr3) (5) by reaction with PhLi, MeLi, and CH2CHCH2MgCl, 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(η5-C5H5)(CHPh2)(CO)(PiPr3) (6) under CO atmosphere. In toluene at 60 °C, complex 5 evolves into its allyl isomer Os(η5-C5H5){η3-CH2CHCH(CH2Ph)}(PiPr3) (7). Complex 2 also reacts with HBF4 and NaOCH3. The reaction with HBF4 leads to [Os(η5-C5H5)(η3-CH2C6H5)Cl(PiPr3)]BF4 (8), which loses HCl to give the hydride-carbyne derivative [OsH(η5-C5H5)(⋮CPh)(PiPr3)]+ (9), while the reaction with NaOCH3 affords the carbyne compound Os(η5-C5H5)(⋮CPh) (PiPr3) (10). In methanol as solvent, complex 10 evolves into the hydride-alkoxycarbene species OsH(η5-C5H5){C(OMe)Ph}(PiPr3) (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.