Coordination chemistry of mercury(ii) with 2-pyridylnitrones: monomers to polymers

Abstract

The coordination chemistry of mercury(II) halides, HgX₂, X = Cl, Br, I, with N-methyl-α-(2-pyridyl)nitrone, L1, and N-t-butyl-α-(2-pyridyl)nitrone, L2, is reported. The structures of 1 : 1 complexes [HgX₂L], X = Cl, L = L1; X = Br, L = L2, 2 : 1 complexes [(HgX₂)₂L], X = Br or I, L = L1; X = Cl or I, L = L2, and a unique compound [(HgBr₂)₅(L2)₃] have been determined. In the 1 : 1 and 1 : 2 complexes, the ligand L1 adopts the anti conformation, and is either monodentate or bridging, while the ligand L2 adopts the syn conformation and acts as a chelate ligand. In the compound [(HgBr₂)₅(L2)₃] the ligand L2 is present in both syn-chelate and anti-bridging bonding modes. Secondary intermolecular bonding, involving O⋯Hg or X⋯Hg interactions, can lead to association of the molecular compounds to form polymers of several kinds. In solution, the complexes are labile and the crystalline products do not necessarily reflect the reaction stoichiometry.