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 PtII 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)A and Z= 4. The structure shows the cation disordered over a mirror plane, with the PtII 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)A, and the metal ion lying 0.282 A 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 PtII ion leaving the top face of the metal centre exposed. Electrochemical studies on [PtL]2+ show an irreversible one-electron reduction at Epc=–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 Epc=–1.48 V vs. ferrocene–ferrocenium.