Palladium Complexes of Methylene-Bridged P-Stereogenic, Unsymmetrical Diphosphines

Optically pure P-stereogenic methylphosphine-boranes P(BH3)PhArMe (Ar = 1-naphthyl (1-Np), 9-phenanthryl (1-Phen), 2-biphenylyl (1-Biph)) have been used to prepare six diphosphines of the type PPhAr-CH2-PR2 (R = Ph or i-Pr; 3-ArR) with a methylene bridge between the phosphorus atoms and a single P-stereogenic moiety. The ligands have been reacted with [PdCl2(COD)] to furnish the corresponding [PdCl2(P-P')] complexes. The reaction with [PdCl(eta(3)-2-methylallyl)](2) and NH4PF6 has produced the expected [Pd(eta(3)-2-methylallyl)(P-P')]PF6 complexes as stable species in solution only for the ligands containing the diisopropylphosphino group. The other ligands produced a mixture of species in solution, from which the dimeric complex [Pd-2(eta(3)-2-methylallyl)(2)(PNpPh-CH2-PPh2)(2)](PF6)(2), and the coordination compound [Pd(PBiphPh-CH2-PPh2)(2)](PF6)(2) could be crystallographically characterized.