Coordination Chemistry and Catalytic Application of Bidentate Phosphaferrocene−Pyrazole and −Imidazole Based P,N-Ligands

The synthesis of new planar chiral P,N-ligands based on 3,4-dimethylphosphaferrocene and either pyrazole or 1-methylimidazole is described. The coordination chemistry of the hemilabile pyrazole derivatives 3a and 3b (a features a methylene bridge between the heterocycles, b an ethylene bridge) was investigated and afforded complexes [Mo(3)(CO)5], cis-[Mo(3)2(CO)4], [Cp*RuCl(3)], [Cp*Ru(3)2]OTf, [Cp*RuCl(3)(PPh3)], and [Pd(η3-allyl)(3)]PF6. Reaction of the imidazole derivatives 4a and 4b with [Pd(η3-allyl)Cl]2 and TlPF6 yielded [Pd(η3-allyl)(4)]PF6. The Pd complexes of 3 and 4 were tested in the catalytic asymmetric allylic alkylation reaction of 1,3-diphenylallyl acetate with sodium dimethylmalonate. X-ray structures of one Ru complex and one Pd complex of 3a were determined.