Synthesis and Structures of Palladium and Platinum A-Frame Complexes Bridged by a Novel Binucleating Ligand, N,N‘-Bis[(2-diphenylphosphino)phenyl]- formamidine

A novel binucleating ligand, N,N‘-bis[(2-diphenylphosphino)phenyl]formamidine (Hdpfam), has been prepared and utilized for the synthesis of homo- and heterobimetallic palladium/platinum complexes M₂R₂(μ-X)(μ-dpfam) (M = Pd, Pt; R = Me, p-Tol, Cl; X = Cl, Br, I; dpfam = N,N‘-bis[(2-diphenylphosphino)phenyl]formamidinate). Treatment of Hdpfam with 2 equiv of MRX(tmeda) or MRX(cod) in the presence of tmeda produced the homobimetallic complexes. The heterobimetallic complex PdPtMe₂(μ-Cl)(μ-dpfam) was obtained by the reaction of PdMeCl(cod) with PtMe(dpfam), which was produced from PtMe₂(cod) and Hdpfam. The crystal structures of Pd₂Cl₂(μ-Cl)(μ-dpfam) and Pt₂Me₂(μ-Cl)(μ-dpfam) have been determined by X-ray analysis. The results indicate that both complexes have P−M−Cl−M−P A-frame structures, in which each metal center has a slightly distorted square-planar geometry and the nonbridging σ-donor ligands (Cl or Me) and μ-Cl are in a cis orientation. Treatment of Pt₂Me₂(μ-Cl)(μ-dpfam) with NaBH₄ gave the hydride-bridged complex Pt₂Me₂(μ-H)(μ-dpfam).