Mono- and di-carbonyl complexes of molybdenum(II) with mixed bidentate ligands. X-Ray crystal structure of [MoBr2(CO)(bipy)(Ph2PCH2PPh2)](bipy = 2,2′-bipyridine): a novel type of [M(bidentate)2(unidentate)3] structure

Abstract

The diphosphine Ph₂PCH₂PPh₂(dppm) reacts with [MoBr₂(CO)₃(bipy)](bipy = 2,2′-bipyridine) or [MoBr₂(CO)₃(phen)](phen = 1,10-phenanthroline) to give the seven-co-ordinate complexes [MoBr₂(CO)₂(bipy)(dppm)](1a) and [MoBr₂(CO)₂(phen)(dppm)](1b) respectively. Sunlight irradiation of (1a) in dichloromethane solution leads to the mixed bidentate monocarbonyl complex [MoBr₂(CO)(bipy)(dppm)](2) which has been characterized by X-ray crystallography. Crystals are orthorhombic, space group Pbca, with a =18.440(7), b= 19.997(6), c= 17.900(9)Å, and Z= 8. The structure has been refined to R= 0.072 and R′= 0.059 from 2 078 reflections with F > 3σ(F). The Mo co-ordination sphere is a distorted pentagonal bipyramid with carbonyl and one bipyridine nitrogen atom in the axial positions. Compound (2) reacts with ligands L, giving cationic species [MoBr(CO)(bipy)(dppm)L]⁺[L = CO, PH₃ P(OMe)₃, P(OPrⁱ)₃, or P(OPh)₃] and [Mo(CO)(bipy)(dppm)L₂]²⁺ when L = P(OCH₂)₃CCH₃.