Synthesis and structural characterisation of the lead–platinum sulfido aggregates [Pt2(μ-S)2(PPh3)4PbX2] (X = Br, I); promotion of rare tetrahedral geometry for lead(II)

The reactions of [Pt2(μ-S)2(PPh3)4] with excess PbBr2 or PbI2 in methanolic suspension result in the formation of the neutral lead(II) halide adducts [Pt2(μ-S)2(PPh3)4PbX2] (X = Br, I). The X-ray structure determination of the lead iodide adduct reveals an essentially tetrahedral lead(II) centre, which is a rare coordination geometry for lead(II), which almost invariably is hemidirected, with a stereochemically active lone pair. In contrast, the structure of the PbBr2 adduct, although suffering from some disorder, shows a more typical, distorted arrangement of ligands; these results are discussed in terms of the tendency for soft, bulky ligands to promote symmetric, holodirected geometries. The ESI mass spectra of the adducts are reported, and yield [M−halide]+ ions.

Graphical abstractThe reaction of [Pt2(μ-S)2(PPh3)4] with excess PbBr2 or PbI2 in methanolic suspension results in the formation of neutral lead(II) halide adducts [Pt2(μ-S)2(PPh3)4PbX2] (X = Br, I) which were characterised by X-ray crystallography and ESI mass spectrometry. The PbI2 adduct, with an essentially tetrahedral, four-coordinate lead, represents a rare example of a holodirected, low coordination lead(II) complex; the structure of the PbBr2 adduct shows the more typical distorted coordination geometry.Figure optionsDownload full-size imageDownload as PowerPoint slide