Crystal structure and spectroscopic properties of mercury(II) halide complexes. Part II. The dimethyl sulphoxide–mercury(II) chloride (2/3) adduct

Abstract

The structure of the title compound was solved from diffractometer data by Patterson and Fourier methods and refined by least-squares techniques to R 8·5% for 1986 observed reflections. Crystals are triclinic, space group P, with unit-cell dimensions: a= 6·672(7), b= 9·286(8), c= 8·764(8)Å, α= 60·0(1), β= 95·5(1), γ= 90·1(2)°, Z= 1. In the asymmetric unit there are two crystallographically independent mercury atoms. One of them bonds covalently to two chlorine atoms at 2·306 Å, and four other chlorine atoms with long contacts (3·004 and 3·081 Å). The co-ordination around the other mercury involves two dimethyl sulphoxide molecules via the oxygen atom at 2·52 and 2·56 Å, two close chlorine atoms at 2·309 and 2·320 Å, and two chlorine atoms of neighbouring molecules at 3·302 and 3·372 Å. The sulphoxide groups are bonded to two mercury atoms so that a bridging centrosymmetric structure is reached. I.r. spectroscopic data are consistent with the presence of two types of nearly linear HgCl₂ moieties. The large frequency shift between ν(S–O) of the free sulphoxide and that of the adducts is ascribed to the bonding of the oxygen atom to two mercury atoms.