Rhodium(I) complexes of α-keto-stabilised 1,2-bis(diphenylphosphino)alkane mono ylides

Abstract

Rhodium(I) complexes of the hybrid ylide-phosphine ligands, Ph₂P(CH₂) _n PPh₂(CHC(O)C₆H₅) (n = 1: dppm-yl, or 2: dppe-yl) have been synthesised from [Rh(μ-C1)(COD)]₂ (COD = 1,5-cyclooctadiene) and characterized by NMR spectroscopic and X-ray structural methods. The dppe-yl behaves as an ambidentate ligand; it functions as a monodentate P-donor ligand with a dangling ylidic carbon in the neutral chloro complex, [(COD)Rh(Cl)(dppe-yl)] (1), whereas replacement of the chloride by a non-coordinating counter anion results in the formation of the complexes, [(COD)Rh(L-L')]+ (L-L' = dppe-yl (2) or dppm-yl (3)) respectively in which the ligands are bonded to the metal via the phosphorus and the ylidic carbon atoms. The 1,5-cyclooctadiene (COD), present in the Rh(I) precursor, remains intact in the products. The structures of 1,2 and3 have been confirmed by X-ray crystallography.