Further studies on the chemistry of tetramethylthiourea–platinum complexes: Evolution of cis-[PtCl{SC(NMe2)2}(PPh3)2]+ to the dinuclear monothiocarbamato–sulfido complex [Pt2(μ-S){μ-SC(O)NMe2}(PPh3)4]+

• [Pt2(μ-S){μ-SC(O)NMe2}(PPh3)4]+ obtained from cis-[PtCl2(PPh3)2] with Me2NC(S)NMe2 (tmtu) and Me3N.
• Structural characterisation and ESI MS confirm dinuclear complex.
• Complex acts as metalloligand towards organomercury species, studied by ESI MS and DFT calculations.
• Intermediate complex cis-[PtCl(tmtu)(PPh3)2]+ structurally characterised as PF6− salt.

Reaction of cis-[PtCl2(PPh3)2] with tetramethylthiourea (tmtu) in methanol under various conditions has been re-investigated. In the absence of base, the simple ligand substitution product [PtCl(tmtu)(PPh3)2]PF6 can be isolated by addition of excess NH4PF6. The complex was characterised by positive-ion ESI mass spectrometry, NMR spectroscopy and an X-ray structure determination. In refluxing methanol with excess Me3N, cis-[PtCl2(PPh3)2] reacts with tmtu to give a yellow solution containing the dinuclear monothiocarbamato complex [Pt2(μ-S){μ-SC(O)NMe2}(PPh3)4]+; the complex was isolated as BPh4− or PF6− salts. The X-ray structure of [Pt2(μ-S){μ-SC(O)NMe2}(PPh3)4]BPh4·CHCl3 is described. ESI mass spectrometry has been used to identify various reaction intermediates and by-products in the synthesis of [Pt2(μ-S){μ-SC(O)NMe2}(PPh3)4]+. [Pt2(μ-S){μ-SC(O)NMe2}(PPh3)4]+ acts as a metalloligand, e.g. towards PhHg+, but a pure product was unable to be isolated. DFT calculations suggest the presence of a Hg⋯OC interaction.

A novel dinuclear product [Pt2(μ-S){μ-SC(O)NMe2}(PPh3)4]+ was obtained from refluxing cis-[PtCl2(PPh3)2] with tetramethylthiourea in the presence of tertiary amine base. The complex, which was structurally characterised, is also able to act as a metalloligand to organomercury(II) species, with DFT calculations suggesting coordination through the sulfido and carbonyl groups.Figure optionsDownload as PowerPoint slide