Notes. X-Ray crystal and molecular structures of [(diphenylphosphinomethyl)diphenylphosphine sulphide]di-iodomercury(II) and [1,2-bis(diphenylphosphinothioyl)ethane]dichloromercury(II)

Abstract

Reaction of mercury(II) iodide with the unsymmetrical diphosphine ligand Ph₂P(S)CH₂PPh₂ resulted in the formation of a solid compound [HgI₂{Ph₂P(S)CH₂PPh₂}] (1), which has been shown by X-ray crystallography to be monomeric with a flattened tetrahedral geometry about the mercury atom. The diphosphine co-ordinates via the sulphur and trivalent phosphorus atoms [Hg–S(1) 2.760(4), Hg–P(2) 2.503(5) Å] forming a five-membered ring; the two remaining tetrahedral sites are occupied by the iodide atoms [Hg–I 2.727(2) and 2.693(2) Å]. Crystals of (1) are monoclinic, space group P2₁/c, with unit-cell dimensions a = 11.426(2), b = 15.491(4), c = 16.324(3) Å, β = 109.79(1), and Z = 4. The structure was refined to final R = 0.059 for 2 632 reflections with I 3.0σ(I). The reaction of mercury(II) chloride with the symmetrical diphosphine Ph₂P(S)CH₂CH₂(S)PPh₂ led to the isolation of the adduct [HgCl₂{Ph₂P(S)CH₂CH₂(S)PPh₂}] (2). Crystallographic studies revealed a distorted tetrahedral mercury centre defined by two chloride atoms [Hg–Cl 2.447(3) and 2.442(3) Å] and a chelating diphosphine ligand which co-ordinates via the sulphur atoms [Hg–S(1) 2.559(3) and Hg–S(2) 2.546(3) Å]. The mode of co-ordination of the diphosphine ligand results in the formation of a seven-membered ring, a result which is unprecedented in phosphine/arsine chalcogenide chemistry. Crystals of (2) are monoclinic, space group P2₁/n, with unit-cell dimensions a = 8.404(4), b = 16.829(3), c = 19.354(3) Å, β = 91.02(3), and Z = 4. The structure was refined to final R = 0.056 for 3 406 reflections with I 2.5σ(I).