Preparation and characterisation of [PPh4][fac-PtX3(S4N4)](X = Cl, Br or I)

Abstract

Reaction of [PPh₄]X (X = Cl or Br) with K₂[PtX₄] in water leads to either [PPh₄]₂[PtCl₄] or a mixture of [PPh₄]₂[PtBr₄] and [PPh₄]₂[Pt₂Br₆], depending upon the halogen present; reaction of PtI₂ with KI and [PPh₄]I leads to [PPh₄]₂[Pt₂I₆] as the sole product. All of these compounds react with S₄N₄ in CH₂Cl₂ to give the platinum(IV) species [PPh₄][PtX₃(S₄N₄)] which contain the S₄N₄^2– ligand. The chloro species may also be obtained by metathesis from K[PtCl₃(S₄N₄)] which is itself prepared by reaction of S₄N₄ with Zeise's salt, K[PtCl₃(C₂H₄)], in tetrahydrofuran. Comparison of the ¹⁵N NMR spectra of labelled complexes with that of [Ir(CO)Cl(S₄¹⁵N₄)(PPh₃)] indicates that in all cases this ligand adopts a facial co-ordination mode, bound by two sulfurs and one nitrogen. Two ²J(¹⁵N–¹⁵N) interactions of magnitude 3 and 5.5 Hz are observed within the ligand.