Amido PNP complexes of iridium: Synthesis and catalytic olefin and alkyne hydrogenation

In situ lithiation of HN(o-C6H4PPh2)(2) (H[1a]) or HN(o-C(6)H(4)PiPr(2))(2) (H[1b]) with nBuLi in THF at -35 degrees C followed by addition of [Ir(mu-Cl)(COD)](2) (COD = 1,5-cyclooctadiene) in toluene at -35 degrees C generates 5-coordinate [1a]Ir(eta(4)-COD) (2a) or 4-coordinate [1b]Ir(eta(2)-COD) (2b), respectively. Oxidative addition of N-H in H[1b] to [Ir(mu-Cl)(COD)](2) affords square pyramidal [1b]Ir(H)(Cl) (3b). Metathetical reaction of 3b with LiBHEt3 in the presence of 1 atm of H-2 in toluene produces [1b]Ir(H)(2) (4b). Both 2a and 4b are active for catalytic hydrogenation of olefins and alkynes under extremely mild conditions.