Platinum thioether macrocyclic chemistry: synthesis and electrochemistry of [PtL][PF6]2(L =[12]-, [14]- or [16]-aneS4) and [Pt2([28]aneS8)][PF6]4. Crystal structure of [Pt([12]aneS4)][PF6]2·MeCN

Abstract

A series of mono- and bi-nuclear platinum(II) complexes [PtL][PF₆]₂(L =[12]-, [14]- or [16]-aneS₄) and [Pt₂([28]aneS₈)][PF₆]₄ have been synthesised by reaction of the crown thioethers with platinum(II) salts. Spectroscopic and structural data confirm square-planar homoleptic thioether co-ordination at Pt^II in each case. The complex [Pt([12]aneS₄)][PF₆]₂·MeCN crystallises in the orthorhombic space group Pnma with a= 16.7983(9), b= 9.3213(7), c= 14.1954(8)Å and Z= 4. The structure shows the cation disordered over a mirror plane, with the Pt^II ion bound to all four thioether donors in a distorted square-planar stereochemistry, Pt–S(1) 2.266(4), Pt–S(4) 2.297(4)Å, and the metal ion lying 0.282 Å above the S₄ co-ordination plane. The methylene carbons of the macrocycle are all directed to the opposite side of the S₄ plane from the Pt^II ion leaving the top face of the metal centre exposed. Electrochemical studies on [PtL]²⁺ show an irreversible one-electron reduction at E_pc=–1.41, –1.45 and –1.50 V vs. ferrocene–ferrocenium for L =[12]-, [14]- and [16]-aneS₄ respectively at a scan rate of 180 mV s^–1. The complex [Pt₂([28]aneS₈)]⁴⁺ exhibits an irreversible two-electron reduction at E_pc=–1.48 V vs. ferrocene–ferrocenium.