Dehydrogenative Addition of Aldehydes to a Mixed NHC-Osmium-Phosphine Hydroxide Complex: Formation of Carboxylate Derivatives

The addition of the O–H bond of [OsH­(OH)­(CPh)­(IPr)­(PiPr3)]­OTf (1; IPr = 1,3-bis­(2,6-diisopropylphenyl)­imidazolylidene, OTf = CF3SO3) to the C–Hα bond of aldehydes is reported. Complex 1 reacts with n-propanal, acrolein, cinnamaldehyde, and benzaldehyde to give the carboxylate-hydride-alkylidyne derivatives [OsH­(κ2-O2CR)­(CPh)­(IPr)­(PiPr3)]­OTf (R = Et (2), CHCH2 (3), CHCHPh (4), Ph (5)) and H2. Complexes 2, 4, and 5 afford the alkylidenes [Os­(κ2-O2CR)­(CO)­(CHPh)­(IPr)­(PiPr3)]­OTf (R = Et (6), CHCHPh (7), Ph (8)) under a CO atmosphere.