Stable diplatinum complexes with functional thiolato bridges from dialkylation of [Pt₂(μ-S)₂(P–P)₂] [P–P = 2 × PPh₃, Ph₂P(CH₂)₃PPh₂]

Abstract

The normally robust monoalkylated complexes [Pt₂(μ-S)(μ-SR)(PPh₃)₄]⁺ can be activated towards further alkylation. Dialkylated complexes [Pt₂(μ-SR)₂(P–P)₂]²⁺ (P–P = 2 × PPh₃, Ph₂P(CH₂)₃PPh₂) can be stabilized and isolated by the use of electron-rich and aromatic halogenated substituents R [e.g. 3-(2-bromoethyl)indole and 2-bromo-4 -phenylacetophenone] and 1,3-bis(diphenylphosphino)propane [Ph₂P(CH₂)₃PPh₂ or dppp] which enhances the nucleophilicity of the {Pt₂(μ-S)₂} core. This strategy led to the activation of [Pt₂(μ-S)(μ-SR)(PPh₃)₄]⁺ towards R–X as well as isolation and crystallographic elucidation of [Pt₂(μ-SC₁₀H₁₀N)₂(PPh₃)₄](PF₆)₂ ( 2a), [Pt₂(μ-SCH₂C(O)C₆H₄C₆H₅)₂(PPh₃)₄](PF₆)₂ ( 2b), and a range of functionalized-thiolato bridged complexes such as [Pt₂(μ-SR)₂(dppp)₂](PF₆)₂ [R = –CH₂C₆H₅ ( 8a), –CH₂CHCH₂ ( 8b) and –CH₂CN ( 8c)]. The stepwise alkylation process is conveniently monitored by Electrospray Ionisation Mass Spectrometry, allowing for a direct qualitative comparison of the nucleophilicity of [Pt₂(μ-S)₂(P–P)₂], thereby guiding the bench-top synthesis of some products observed spectroscopically.