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 dz2 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.