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

Rhodium(I) complexes of the hybrid ylide-phosphine ligands, Ph2P(CH2)nPPh2(CHC(O)C6H5) (n = 1: dppm-yl, or 2: dppe-yl) have been synthesized from [Rh(m-Cl)(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 and 3 have been confirmed by X-ray crystallography.