Tuning the sulfur–heterometal interaction in organolead(IV) complexes of [Pt 2(μ-S) 2(PPh 3) 4

Abstract

Reactions of [Pt 2(μ-S) 2(PPh 3) 4] with Ph 3PbCl, Ph 2PbI 2, Ph 2PbBr 2 and Me 3PbOAc result in the formation of bright yellow to orange solutions containing the cations [Pt 2(μ-S) 2(PPh 3) 4PbR 3] + (R 3 = Ph 3, Ph 2I, Ph 2Br, Me 3) isolated as PF 6 − or BPh 4 − salts. In the case of the Me 3Pb and Et 3Pb systems, a prolonged reaction time results in formation of the alkylated species [Pt 2(μ-S)(μ-SR)(PPh 3) 4] + (R = Me, Et). X-ray structure determinations on [Pt 2(μ-S) 2(PPh 3) 4PbMe 3]PF 6 and [Pt 2(μ-S) 2(PPh 3) 4PbPh 2I]PF 6 have been carried out, revealing different coordination modes. In the Me 3Pb complex, the (four-coordinate) lead atom binds to a single sulfur atom, while in the Ph 2PbI adduct coordination of both sulfurs results in a five-coordinate lead centre. These differences are related to the electron density on the lead centre, and indicate that the interaction of the heterometal centre with the {Pt 2S 2} metalloligand core can be tuned by variation of the heteroatom substituents. The species [Pt 2(μ-S) 2(PPh 3) 4PbR 3] + display differing fragmentation pathways in their ESI mass spectra, following initial loss of PPh 3 in all cases; for R = Ph, loss of PbPh 2 occurs, yielding [Pt 2(μ-S) 2(PPh 3) 3Ph] +, while for R = Me, reductive elimination of ethane gives [Pt 2(μ-S) 2(PPh 3) 3PbMe] +, which is followed by loss of CH 4.