Rhodium and iridium complexes containing diphenyl-2-(3-methyl)indolylphosphine: synthesis, structure and application in the catalytic transfer hydrogenation of ketones

Abstract

The synthesis and characterisation of a number of group nine complexes containing the recently reported ligand, diphenyl-2-(3-methyl)indolylphosphine, is presented herein. The complexes [RhCl(COD){PPh₂(C₉H₈N)}] (1), [IrCl(COD){PPh₂(C₉H₈N)}] (2), [RhCl(NBD){PPh₂(C₉H₈N)}] (3) and [Rh(COD)(MeCN){PPh₂(C₉H₈N)}]BF₄ (4) (where COD = 1,5-cyclooctadiene, NBD = 2,5- norbornadiene) have been structurally characterised by X-ray crystallography. The complex [Rh₂(COD)₂{N(Me)C(H)Ph)}{PPh₂(C₉H₈N)}][BF₄]₂ (8) was also isolated and structurally characterised. Complex 8 contains a ‘[Rh(COD)]’ fragment coordinated to the aromatic ring of the indolyl group, providing the first example of a η⁶ coordination mode for this ligand. The synthesised complexes were investigated for their activity in the catalytic transfer hydrogenation of ketones and found to be moderately active catalysts.