X-ray and NOE studies on trinuclear iridium hydride phosphino oxazoline (PHOX) complexes

Two trinuclear iridium hydride clusters of the type [Ir-3(mu(3)-H)(H)(6)(PHOX)(3)]X1X2 (X-1 = PF6, X-2 = OTf; X-1 = X-2 = PF6; X-1 = X-2 = OTf; PHOX = (S)-4-tent-butyl-2-[2-(di-o-tolylphosphinyl)phenyl]-4,5-dihydrooxazole, (S)-2-[2-(diphenylphosphinyl)phenyl]-4-isopropyl-4,5-dihydrooxazole) have been prepared and characterized by X-ray diffraction and multidimensional NMR. They contain a single bridging hydride in pseudo-trans position to the P-donors. The complexed PHOX ligands reveal a chiral pocket involving one pseudoequatorial P-aryl substituent and one pseudoaxial (proximate to the oxazoline substituent) P-aryl group. These trinuclear complexes are shown to be inactive as hydrogenation catalysts.