Metallophilic Contacts in 2-C₆F₄PPh₂ Bridged Heterobinuclear Complexes: A Crystallographic and Computational Study

(Figure Presented) Treatment of the bis(chelate) complex trans-[Pd(κ²-2-C₆F₄PPh₂)₂] (7) with PMe₃ gave trans-[Pd(κC-2-C₆F₄PPh₂)₂(PMe₃)₂] (13) as a mixture of syn- and anti-isomers. Reaction of 13 with CuCl, AgCl, or [AuCl(tht)] (tht = tetrahydrothiophene) gave the heterobinuclear complexes [(Me₃P)₂Pd(μ-2-C₆F₄PPh₂)₂MCl] [M = Cu (14), Ag (15), Au (16)], from which the corresponding salts [(Me₃P)₂Pd(μ-2-C₆F₄PPh₂)₂M]PF₆ [M = Cu (17), Ag (18), Au (19)] could be prepared by abstraction of the chloro ligand with TlPF₆; 18, as well as its triflato (20) and trifluoroacetato (21) analogues, were also prepared directly from 13 and the appropriate silver salt. Reaction of 13 with [AuCl(PMe₃)] gave the zwitterionic complex [(Me₃P)PdCl(μ-2-C₆F₄PPh₂)₂Au] (24) in which the 2-C₆F₄PPh₂ ligands are in a head-to-head arrangement. In contrast, the analogous reaction with [AuCl(PPh₃)] gave [(Ph₃P)PdCl(μ-2-C₆F₄PPh₂)₂Au] (25) with a head-to-tail ligand arrangement. Single crystal X-ray diffraction studies of complexes 14-21 show short metal-metal separations [2.7707(11)-2.9423(3) Å] suggestive of attractive noncovalent (dispersion) interactions, a conclusion that is supported by theoretical calculations of the electron localization function and the noncovalent interactions descriptor.