Iridium Half-Sandwich Complexes with Di- and Tridentate Bis(pyridylimino)isoindolato Ligands: Stoichiometric and Catalytic Reactivity

Abstract

A series of κ 2 -(N,N)-coordinated bis(2-pyridylimino)isoindolato (BPI) complexes [Cp∗Ir(BPI)Cl], which possess "three-legged piano-stool" structures, with the iridium atom being coordinated by the Cp∗ ligand 2 × N and Cl, were prepared via deprotonation of the BPIH ligands with either potassium hydride or LDA and subsequent reaction with [Cp∗IrCl 2 ] 2 in THF. Cationic complexes [Cp∗Ir(BPI)] + containing κ 3 -(N,N,N)-coordinated BPI ligands were prepared as well as complexes with bidentate-coordinated BPI ligands, where the chloride ligand was substituted by either neutral or anionic ligands. Substitution in the ortho-position of the PBI ligands led to the formation of cycloiridated κ 3 -(N,N,C) species. Upon substitution of the anionic ligand by triphenylphosphine, a product was obtained with a hitherto unobserved κ 2 -(N,N) coordination of oMe-BPI to the metal center via the deprotonated nitrogen atom of the isoindole unit and one of the imine nitrogen atoms of the BPI ligand. A series of (para-cymene) osmium half-sandwich complexes with analogous structures and reactivities to their isoelectronic Cp∗Ir(BPI) congeners were also prepared. Finally, it has been demonstrated that both Ir and Os complexes are catalytically active in the transfer hydrogenation of various ketones and imines. (Chemical Equation Presented).