The Effect of Substituents at Lewis Acidic Bismuth(III) Centers on Its Propensity to Bind a Noble Metal Donor.

To investigate the effect of X in ambiphilic compounds BiX(o-PPh2-C6H4)2, PBiP-X, on metallophilic Pt-Bi interactions in its PtCl2 complexes two new derivatives PBiP-Me and PBiP-C6F5 were synthesized. Reaction with dichloro(1,5-cyclooctadiene)platinum(II) led to the platinum(II) complexes [PtCl2(PBiP-Me)], 3, and [PtCl2(PBiP-C6F5)], 4, which together with the halide [PtCl2(PBiP-Cl)], 2, reported previously, establish a series of related PBiP-X complexes differing only in X. This could be complemented by accessing [PtCl2(PBiP-OTf)], 5, through the reaction of 2 with AgOTf. Analysis of the geometrical and electronic structures of these complexes revealed that in all cases the platinum(II) centers act as donors (through their filled d(z(2)) orbitals) to the bismuth(III) centers (possessing σ*(Bi-X)/6p acceptor orbitals). The strength of these interactions increases with increasing electron-withdrawing character of X, which supports the conceptual approach in constructing this new class of compounds.