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.