Combined Experimental/Computational Study of Iridium and Palladium Hydride PP(O)P Pincer Complexes

The diphosphine–phosphine oxide {[o-iPr2P­(C6H4)]2P­(O)­H} (1) has been prepared, and its coordination to Ir and Pd has been explored. Using [IrCl­(cyclooctene)2]2, the pincer hydride complex {(o-iPr2PC6H4)2P­(O)]­IrHCl} (2) is readily obtained by phosphine-assisted P­(O)–H bond activation. Coordination of CO to Ir affords the corresponding octahedral complex {(o-iPr2PC6H4)2P­(O)]­IrHCl­(CO)} (3) as a single stereoisomer. The electronic properties of the PP­(O)­P ligand have been compared with those of related PEP frameworks on the basis of νCO stretching frequencies. Treatment of 1 with [Pd­(PtBu3)2] gives the palladium hydride complex {(o-iPr2PC6H4)2P­(O)]­PdH} (4). The mechanism of P­(O)–H bond activation at Pd has been investigated computationally. Complex 4 reacts with methyl acrylate at room temperature, giving {(o-iPr2PC6H4)2P­(O)]­PdCH­(Me)­CO2Me} (7) as the result of regioselective insertion into the Pd–H bond.