Metallophilic interactions: observations of the shortest metallophilicinteractions between closed shell (d10⋯d10, d10⋯d8, d8⋯d8) metal ions [M⋯M′ M = Hg(ii) and Pd(ii) and M′ = Cu(i), Ag(i), Au(i), and Pd(ii)]

Abstract

The salt metathesis reaction of two equivalents of 8-lithioquinoline (C₆H₆NLi) with HgBr₂ afforded bis(quinoline-8-yl)mercury, [(C₆H₆N)₂Hg]. Bis(quinoline-8-yl)mercury has been used for the synthesis of a series of heteronuclear complexes of the type [(C₆H₆N)₂M·M′]·X⁻_n [M = Hg; {M′ = Cu, X⁻ = ClO₄; X = I; X⁻ = CF₃SO₃}, {M′ = Ag, X⁻ = ClO₄; X⁻ = CF₃SO₃; X⁻ = BF₄}, {M′ = Au, X⁻ = CF₃SO₃}; {M′ = Pd, X⁻ = CF₃CO₂}], [M = Pd; M′ = Pd, X⁻ = CF₃CO₂; n = 2]. All the complexes were well characterized by multinuclear NMR (¹H, ¹³C, ¹⁹F, ¹¹B, ¹⁹⁹Hg) spectroscopic analysis. Their structures were determined by single crystal X-ray diffraction studies, which displayed the shortest Hg⋯M′ (M′ = Cu, Ag, Au, Pd) metallophilic interactions. The electronic properties of the molecular structures were determined by DFT calculations. ELF (Electron Localization Function) analysis provided the information about the localization of electrons between metal⋯metal bonds and dispersion of electron density around the metal ions. The AIM (Atoms in Molecule) analysis revealed the presence of electron density at the bond critical points (bcp) and the strengths of M⋯M′ [M = Hg, M′ = Cu, Ag, Au, Pd; M, M′=Pd] interactions. The NBO (Natural Bond Orbital) analysis was used to identify the donor–acceptor character of the orbitals involved in the bonding.