Synthesis, platinum-195 nuclear magnetic resonance spectroscopic and extended X-ray absorption fine structure studies on platinum-(II) and -(IV) thioether macrocyclic complexes

Reaction of [PtL][PF6](2) (L = [12]aneS(4) = 1,4,7,10-tetrathiacyclododecane, [14]aneS(4) = 1,4,8,11-tetrathiacyclotetradecane or [16]aneS(4) = 1,5,9,13-tetrathiacyclohexadecane) with Cl-2-CCl4 or Br-2-CCl4 in MeCN solution afforded the corresponding platinum(IV) species [PtX(2)L][PF6](2) in high yield as yellow (X = Cl) or orange (X = Br) solids. These species have been characterised by IR spectroscopy, FAB mass spectrometry and microanalytical data. Platinum-195 NMR spectroscopic studies on the parent platinum(II) complexes and on the platinum(IV) oxidation products confirm S-4 and S(4)X(2) donor sets respectively. These studies also indicate that [PtX(2)([16]aneS(4))][PF6](2) probably exist as trans-dihalides, whereas [PtX(2)([12]aneS(4))][PF6](2) and [PtX(2)([14]aneS(4))][PF6](2) are probably cis-dihalides. The crystal structure of [Pt([16]aneS(4))][PF6](2) . 2MeCN shows the Pt-II occupying a crystallographic inversion centre, co-ordinated to a square-planar tetrathia donor set with the free S-based lone pairs adopting the up, up, down, down configuration, Pt-S 2.310(2) Angstrom. Platinum L-III edge EXAFS (extended X-ray absorption fine structure) data have been recorded for these complexes. The Pt-S bond lengths for the platinum(II) complexes compare well with those derived from single-crystal X-ray crystallography, while the Pt-S and Pt-X distances determined from EXAFS studies for the, platinum(Iv) complexes show that oxidation of Pt-II to Pt-IV typically results in a slight lengthening of the Pt-S bond lengths.