New Hg(II)–N-heterocyclic carbene complexes of compartmental ligands with a suitable topology for a η1-arene–Hg(II) close interaction

Abstract

A new Hg(II)–N-heterocyclic carbene (NHC) complex (1) of the form [(NHC)2-μ-Hg]·2PF6 was synthesized from the reaction of Hg(II) acetate with a meta-xylyl-linked bis-imidazolium salt (η1-areneC–H model). The complex was characterized using elemental analysis, nuclear magnetic resonance (1H, 13C and HMQC), and single-crystal X-ray diffraction techniques. X-ray structural studies on complex 1 revealed a linear coordination of the Hg ion with both carbene centers of the ligand. In addition, a strong interaction between the Hg ion and a carbon atom of the aryl ring of the ligand was also observed. This interesting interaction is further supported by a downfield chemical shift of the 1H NMR signal for the arene-H that interacts with mercury (δ 0.88 compared to the free ligand). In a related meta-arylene-bis(imidazol-2-yliden-1-ylmethyl) Hg(II) complex (2) with a methyl group between the bridges, synthesized in analogy to complex 1, no such interaction between the Hg ion and the aryl ring was observed.