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)­(P^<i>i</i>Pr₃)]­OTf (<b>1</b>; IPr = 1,3-bis­(2,6-diisopropylphenyl)­imidazolylidene, OTf = CF₃SO₃) to the C–H_α bond of aldehydes is reported. Complex <b>1</b> reacts with <i>n</i>-propanal, acrolein, cinnamaldehyde, and benzaldehyde to give the carboxylate-hydride-alkylidyne derivatives [OsH­(κ²-O₂CR)­(CPh)­(IPr)­(P^<i>i</i>Pr₃)]­OTf (R = Et (<b>2</b>), CHCH₂ (<b>3</b>), CHCHPh (<b>4</b>), Ph (<b>5</b>)) and H₂. Complexes <b>2</b>, <b>4</b>, and <b>5</b> afford the alkylidenes [Os­(κ²-O₂CR)­(CO)­(CHPh)­(IPr)­(P^<i>i</i>Pr₃)]­OTf (R = Et (<b>6</b>), CHCHPh (<b>7</b>), Ph (<b>8</b>)) under a CO atmosphere