BIPHOSPHOLE - A C-2 SYMMETRY CHIRAL BIDENTATE LIGAND - SYNTHESIS AND CHARACTERIZATION OF NICKEL, PALLADIUM, PLATINUM, AND RHODIUM COMPLEXES

Owing to the C-2 symmetry structure of '-diphenyl-3,3',4,4'-tetramethy l-2,2'-biphosphole, 1 (BIPHOS), we investigated the coordination of th is chiral bidentate ligand to transition metals in order to explore th e potential of these complexes in asymmetric catalysis. Nickel, pallad ium, and platinum complexes [M(BIPHOS)X(2)] (2 (M = Ni, X = Br), 3 (M = Pd, X = Cl), 4 (M = Pt, X = Cl) were synthesized and fully character ized. Their structures were determined by X-ray crystallography. The c ationic palladium complexes [Pd(BIPHOS)(CH3-CN)(2)](BF4)(2), 6, and [P d(BIPHOS)(eta(3)-C3H5)]Cl, 7, were also synthesized. The pi-allylpalla dium complex 7 reveals a potential interest for catalytic allylic subs titution. The reaction of 1 with [Pd(CH3CN)(4)](BF4)(2) leads to the f ormation of the meso diastereoisomer [Pd(BIPHOS)(2)] (BF4)(2), 5, whic h was fully characterized. Its structure was determined by X-ray cryst allography. A bis(BIPHOS) complex of Rh(I), 8, was also obtained by re action of 1 with [Rh(COD)Cl](2) or [Rh(COD)(2)]BF4.