MERCURY POLYSULFIDE COMPLEXES, [HG(SX)(SY)]2- - SYNTHESES, HG-199 NMR-STUDIES IN SOLUTION, AND CRYSTAL-STRUCTURE OF (PH4P)4[HG(S4)2]BR2

Mercury polysulfide complexes [Hg(S(x))(S(y))]2- have been prepared in DMF solution by the reaction HgS + Na2S + S8. The nominal compositions [Hg(S(m))n] of these solutions can be varied widely, with the average polysulfide chain length m ranging from 3 to 8 and the nominal ligand to metal ratio n ranging from 2 to 4. Hg-119 NMR spectroscopy reveals the existence of at least three distinct [Hg(S(x))(S(y))]2- complexes that are in equilibrium and undergo chemical exchange which is slow on the NMR time scale at room temperature. The three principal species are [Hg(S4)2]2-, [Hg(S4)(S5)]2-, and [Hg(S5)2]2-, and there is evidence for [Hg(S5)(S6)]2-. Addition of Ph4Br to the [Hg(S4)2]2- solution causes crystallization of the new complex (Ph4P)4[Hg(S4)2]Br2 (1), which contains well-separated tetrahedral [Hg(S4)2]2-, Ph4P+, and Br- ions, with no secondary bonding. Crystal data for 1: space group I4BAR, a = 19.563 (4) angstrom, c = 11.531 (2) angstrom, V = 4413 (1) angstrom-3, Z = 2 ([Hg(S4)2](PPh4)4Br2), 1661 independent observed reflections (Mo K-alpha, I/sigma(I) > 3), R = 0.024.