PBiP Pincer Complexes of Platinum, Palladium, and Iridium Featuring Metal–Metal Bonds Synthesized by Oxidative Addition of Bismuth–Halide Bonds

The compound BiCl­(o-PPh2-C6H4)2, PBiP-Cl,
which in previous work had been
shown to form complexes with pronounced M→Bi character,
when metal­(I) ions of group 11 or PtII and PdII ions were coordinated, behave differently in contact with late metal
atoms in low oxidation states, known to easily undergo oxidative additions:
Treatment of PBiP-Cl with M­(PPh3)4, with M =
Pt, Pd, led to the formal insertion of M into the Bi–Cl bond
to yield complexes [MCl­(PBiP)]. Analogues PBiP-X with X = Br, I that
could be accessed behaved similarly, producing [MX­(PBiP)]. Both types
of complexation reactionscoordination of PBiP-Cl as an ambiphilic
ligand and oxidative additionwere observed to occur when [Ir­(acac)­(cod)]
was chosen as the precursor compound. NMR investigations clearly indicated
the presence of [IrI(acac)­(PBiP-Cl)] and [IrIII(acac)­Cl­(PBiP)] beside each other in solution, from which, however,
only [IrIII(acac)­Cl­(PBiP)] could be crystallized. DFT results
showed that both products differ only slightly in energy. Reaction
of PBiP-Cl with [Ir­(acac-F6)­(cod)] led only to the iridium­(III)
product, underlining that electronic effects sensitively influence
the course of reactivity and the position of the equilibrium.