Nature of M–Bi bonds in dihalobismuth complexes of nickel, palladium and platinum trans-[X(PMe3)2M(BiX2] (M = Ni, Pd, Pt; X = Cl, Br, I): A theoretical study

Geometry, electronic structure and bonding energy analysis of the terminal neutral dihalobismuth complexes of nickel, palladium and platinum trans-[X(PMe3)2M(BiX2)] (M = Ni, Pd, Pt; X = Cl, Br, I) were investigated at the BP86/TZ2P/ZORA level of theory. The calculated geometrical parameters of platinum complex trans-[Cl(PMe3)2Pt(BiCl2)] are in excellent agreement with structurally characterized platinum complex trans-[Cl(PCy3)2Pt(BiCl2)]. The variations in the M–Bi bond distances show that the trans effect of halides is relatively greater than the effects of halides bonded to the Bi atom. Hence, the strength of the M–Bi bond decreases on going from X = Cl to X = I in the complexes trans-[X(PMe3)2M(BiX2)]. From the perspective of covalent bonding, however π-symmetry contributions are, in all complexes, significantly smaller than the corresponding σ bonding contribution. Thus, in these complexes, the [BiX2] behaves predominantly as a σ donor. The natural population analysis (NPA) charge distributions indicate the bismuth atom carries a significant positive charge in all cases. The contributions of the electrostatic interactions ΔEelstat are significantly larger in all bismuth complexes (I–IX) than the covalent bonding ΔEorb. The interaction energy increases in the order Ni < Pd < Pt, and the absolute values of the ΔEPauli, ΔEint and ΔEelstat contributions to the M–Bi bonds decrease according to X = Cl > Br > I.