Comparative Study of the Structures and Reactivities of Cationic Nickel and Palladium Complexes with a Bismuth-Bisphosphine (PBiP) Ligand

We report the synthesis, structural characterization, and reactivity of a new series of cationic nickel and palladium complexes featuring a bismuth-bisphosphine (PBiP) ligand. By converting neutral R₂Bi–transition metal precursors into cationic species, we enhanced Bi–transition metal bond polarization, thereby enabling unique interactions between bismuth and the transition metal centers. Cationic BiPd^AcN was synthesized via chloride abstraction from BiPd^Cl, yielding a species in which the Bi–Pd bond is best described as a Pd(0) → Bi(III) donor–acceptor interaction based on natural bond orbital (NBO) analyses. This interaction exerts a trans influence, as evidenced by the elongation of the Pd–acetonitrile bond. In contrast, the corresponding BiNi complexes, prepared in a single-step synthesis of BiNi^Cl followed by transformation into BiNi^AcN and BiNi^2AcN, exhibit a more covalent Bi–Ni bond with minimal trans influence from bismuth. Structural analyses, including X-ray diffraction and NMR spectroscopy, reveal differences in coordination geometries and bond metrics between the Ni and Pd systems. Orbital analysis further substantiates that while the Bi–Pd interaction in the cationic species is highly polarized toward Pd, the Bi–Ni bond is more evenly distributed.