A novel structural rearrangement reaction of dialkylated derivatives of [Pt ₂ (μ-S) ₂ (PPh ₃) ₄] involving Pt-C bond formation

Abstract

Reaction of [Pt ₂ (μ-S) ₂ (PPh ₃) ₄] with the dialkylating agents ClCH ₂ C(O)CH ₂ Cl or ClCH ₂ C(NNHC(O)NH ₂)CH ₂ Cl gives the dicationic di-μ-thiolate complexes [Pt ₂ {μ-SCH ₂ C(O)CH ₂ S)(PPh ₃) ₄] ²⁺ or [Pt ₂ {μ-SCH ₂ C(NNHC(O)NH ₂)CH ₂ S} (PPh ₃) ₄] ²⁺, isolated as BPh ₄ ⁻ salts and characterised by ESI mass spectrometry, NMR spectroscopy and single-crystal X-ray crystallography. Treatment of the complex [Pt 2{μ-SCH 2C(O)CH 2S)(PPh₃) ₄] ²⁺, which contains a [6.6.4] bicyclic system, with hydroxide ions results in deprotonation of a CH 2 group and rearrangement of the resulting monocation, giving [Pt ₂ (μ-SCH ₂ C(O)CHS}(PPh ₃) ₄] ⁺, isolated as its PF ₆ ⁻ salt. An X-ray structure determination shows the complex to have a novel rearranged [6.5.5] bicyclic system containing a Pt-S-Pt-S-C five-membered ring with a Pt-C bond. The alkyl ligand has a high trans-influence, manifest in a long trans Pt-P bond and small 1J(PtP) coupling constant to the trans PPh 3 ligand. Reaction of [Pt ₂ (μ-S) ₂ (PPh ₃) ₄] with the 2,4-dinitrophenylhydrazone derivative of 1,3-dichloroacetone leads to the closely related complex [Pt ₂ {μ-SCH ₂ C(NNHAr)CHS} (PPh ₃) ₃Cl] [Ar = C ₆H ₃ (NO ₂) ₂] in which a PPh ₃ ligand is substituted by a chloride.