A novel structural rearrangement reaction of dialkylated derivatives of [Pt2(μ-S)2(PPh3)4] involving Pt–C bond formation

Abstract

Reaction of [Pt₂(μ-S)₂(PPh₃)₄] with the dialkylating agents ClCH₂C(O)CH₂Cl or ClCH₂C(NNHC(O)NH₂)CH₂Cl gives the dicationic di-μ-thiolate complexes [Pt₂{μ-SCH₂C(O)CH₂S)(PPh₃)₄]²⁺ or [Pt₂{μ-SCH₂C(NNHC(O)NH₂)CH₂S}(PPh₃)₄]²⁺, isolated as BPh₄⁻ salts and characterised by ESI mass spectrometry, NMR spectroscopy and single-crystal X-ray crystallography. Treatment of the complex [Pt₂{μ-SCH₂C(O)CH₂S)(PPh₃)₄]²⁺, which contains a [6.6.4] bicyclic system, with hydroxide ions results in deprotonation of a CH₂ group and rearrangement of the resulting monocation, giving [Pt₂(μ-SCH₂C(O)CHS}(PPh₃)₄]⁺, isolated as its PF₆⁻ 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 PPh₃ ligand. Reaction of [Pt₂(μ-S)₂(PPh₃)₄] with the 2,4-dinitrophenylhydrazone derivative of 1,3-dichloroacetone leads to the closely related complex [Pt₂{μ-SCH₂C(NNHAr)CHS}(PPh₃)₃Cl] [Ar = C₆H₃(NO₂)₂] in which a PPh₃ ligand is substituted by a chloride.