HOMOLEPTIC CYCLOHEXANETHIOLATO COMPLEXES OF MERCURY(II)

The complexes Hg(SR)2 1 and [NR'4] (Hg(SR)3] (R' = Et 2 or Me 3) have been obtained from the reaction of HgCl2 with NaSR in acetonitrile, with [NR'4]Cl also present for complexes 2 and 3; SR is cyclohexanethiolate. Complex 1 has a polymeric structure consisting of rather bent Hg(SR)2 units [Hg-S 2.372(2) and 2.374(2) angstrom, S-Hg-S 160.4(1)-degrees] linked together by weaker Hg-S bonds [3.004(2) and 2.959(2) angstrom]; the Hg atoms have highly distorted tetrahedral co-ordination and each thiolate acts as a very asymmetric bridge between two Hg atoms. Complex 2 contains Hg atoms in a distorted trigonal-planar co-ordination environment, the monomeric anions being well separated from each other. The distortion is mostly in-plane, producing one angle considerably less than, and one considerably greater than, the ideal 120-degrees; the largest angle lies opposite the longest Hg-S bond, and the smallest angle opposite the shortest Hg-S bond. Proton and C-13 NMR, far-IR and Raman, and low-energy UV spectroscopic data are discussed. The UV data afford additional support for the proposal of a trigonal-planar [Hg(CysS)3]-co-ordination environment for the metal receptor site of the MerR metalloregulatory protein. A correlation of co-ordination geometry, Hg-S bond lengths, and Hg-S stretching frequencies is developed for these and other homoleptic thiolate complexes of mercury.