Noble metals meet a heavyweight: A pincer ligand brings together bismuth with gold and platinum, so that metallophilic interactions are established. According to DFT calculations, these interactions contain dominant metal→bismuth contributions.

No abstract

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.

The compound BiCl(o-PPh 2 -C 6 H 4 ) 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(PPh 3 ) 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 [Ir I (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.

Reaction of [Cp(2)MoH(2)] with bismuth allyloxide, [Bi{OCH(CH(3))CH==CH(2)}(3)], gave rise to an extended octanuclear complex wherein two cyclic Mo(2)Bi(2) units composed of four Mo-Bi bonds are linked by a Bi-Bi bond. The fact that the construction of such an assembly could be accomplished only in the case of a monomethylation of the parent allyl residue demonstrates a subtle substituent effect.