New hydridoirida-β-diketones derived from 8-quinoline-carbaldehyde and o-(diphenylphosphino)benzaldehyde

Abstract

8-Quinoline-carbaldehyde (C₉H₆NCHO) reacts in methanol with [IrCl(Cod)]₂ (Cod = 1,5-cyclooctadiene) to give the acylhydrido complex [IrHCl(C₉H₆NCO)(Cod)] (1) or with [IrHCl{PPh₂(o-C₆H₄CO)}(Cod)] to afford the hydridoirida-β-diketone complex [IrHCl({PPh₂(o-C₆H₄CO)}(C₉H₆NCO)H)] (2). Complex 2 reacts with silver perchlorate in the presence of pyridine to afford the cationic [IrH({PPh₂(o-C₆H₄CO)}(C₉H₆NCO)H)(py)]ClO₄ (3), which in solution transforms slowly into the cationic dinuclear complex [Ir{μ-PPh₂(o-C₆H₄CO)}(C₉H₆NCO)(py)]₂(ClO₄)₂ (4) with two acylphosphine chelate-bridging ligands. The reaction of 2 with AgClO₄ in the presence of carbon monoxide affords [IrH({PPh₂(o-C₆H₄CO)}(C₉H₆NCO)H)(CO)]ClO₄ (5), which in solution is in equilibrium with the deprotonated diacylhydrido complex [IrH{PPh₂(o-C₆H₄CO)}(C₉H₆NCO)(CO)] (6). The reaction of 2 with Et₃OPF₆ results in the formation of [[IrH({PPh₂(o-C₆H₄CO)}(C₉H₆NCO)H)]₂(μ-Cl)]PF₆ (7), containing a cationic dinuclear species with a single chlorine atom bridging two hydridoirida-β-diketone fragments. The reaction of 2 with [Rh(OMe)(Cod)]₂ affords the hydridoirida-β-diketonaterhodium(I) complex [IrHCl{μ-PPh₂(o-C₆H₄CO)}(μ-C₉H₆NCO)Rh(Cod)] (8), which isomerizes to the thermodynamically stable isomer [IrCl{PPh₂(o-C₆H₄CO)}(μ-H)(μ-C₉H₆NCO)Rh(Cod)] (9). The catalytic activity of these complexes in the hydrogen transfer from isopropanol to cyclohexanone has been tested. The X-ray diffraction structures of complexes 2, 4 and 9 are reported.