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 Pt-II and Pd-II 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-CI 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 [Ir-III(acac)(PBiP-Cl)] and [Ir-III(acac)Cl(PBiP)] beside each other in solution, from which, however, only [Ir-III(acac)Cl(PBiP)] could be crystallized. DFT results showed that both products differ only slightly in energy. Reaction of PBiP-Cl with [Ir(acac-F-6)(cod)] led only to the iridium(III) product, underlining that electronic effects sensitively influence the course of reactivity and the position of the equilibrium.