Tuning the sulfur–heterometal interaction in organolead(IV) complexes of [Pt2(μ-S)2(PPh3)4]

Reactions of [Pt2(μ-S)2(PPh3)4] with Ph3PbCl, Ph2PbI2, Ph2PbBr2 and Me3PbOAc result in the formation of bright yellow to orange solutions containing the cations [Pt2(μ-S)2(PPh3)4PbR3]+ (R3 = Ph3, Ph2I, Ph2Br, Me3) isolated as PF6− or BPh4− salts. In the case of the Me3Pb and Et3Pb systems, a prolonged reaction time results in formation of the alkylated species [Pt2(μ-S)(μ-SR)(PPh3)4]+ (R = Me, Et). X-ray structure determinations on [Pt2(μ-S)2(PPh3)4PbMe3]PF6 and [Pt2(μ-S)2(PPh3)4PbPh2I]PF6 have been carried out, revealing different coordination modes. In the Me3Pb complex, the (four-coordinate) lead atom binds to a single sulfur atom, while in the Ph2PbI 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 {Pt2S2} metalloligand core can be tuned by variation of the heteroatom substituents. The species [Pt2(μ-S)2(PPh3)4PbR3]+ display differing fragmentation pathways in their ESI mass spectra, following initial loss of PPh3 in all cases; for R = Ph, loss of PbPh2 occurs, yielding [Pt2(μ-S)2(PPh3)3Ph]+, while for R = Me, reductive elimination of ethane gives [Pt2(μ-S)2(PPh3)3PbMe]+, which is followed by loss of CH4.

Reactions of [Pt2(μ-S)2(PPh3)4] with Me3PbOAc and Ph2PbI2 result in the formation of the cationic adducts [Pt2(μ-S)2(PPh3)4PbMe3]+ and [Pt2(μ-S)2(PPh3)4PbPh2I]+, which were found from X-ray structure determinations on their hexafluorophosphate salts to contain four- and five-coordinate lead atoms, respectively. Fragmentation pathways of these and other related adducts are reported.Figure optionsDownload as PowerPoint slide