Anion and Solvent Effects upon the Structures of Platinum( <scp>II</scp> ) Complexes with Thiacrown Ligands: The Crystal Structures of [Pt(9S3) 2 ](PF 6 ) 2 ·2 CH 3 NO 2 , [Pt(9S3) 2 ](BF 4 ) 2 ·2 CH 3 NO 2 , [Pt(9S3) 2 ](OTf) 2 ·2 CH 3 NO 2 , and [Pt(18S6)](BF 4 ) 2

The synthesis and crystal structures of four mononuclear PtII homoleptic complexes with two thiacrown ligands are presented. The binding mode for both macrocycles to the platinum center contrasts with previous structural reports involving identical complex cations but differing anions or crystallization solvents. All three bis(1,4,7-trithiacyclononane(9S3))platinum(II) complexes (with tetrafluoroborate, hexafluorophosphate, and triflate as counterions) are centrosymmetric, with endodentate binding of the trithioether resulting in [S4 + S2] coordination. The PtII complex of 1,4,7,10,13,16-hexathiacyclooctadecane(18S6) shows an elongated square pyramidal structure with one exodentate sulfur in a [S4 + S1] mode. Our work illustrates how changes of counterion and solvent dramatically affect the crystal structures for such complexes, suggesting that packing forces are more important than ligand conformation in determining solid-state structures. In addition, the full spectroscopic and electrochemical properties of the complex [Pt(18S6)](BF4)2 are reported. The electronic spectrum shows a d−d transition near 430 nm, and an irreversible PtII/PtIII couple occurs at +564 mV vs. Fc/Fc+ in cyclic voltammetry. Both these data are consistent with other hexakis(thioether) PtII complexes. 13C NMR measurements show a non-fluxional 18S6 ligand in the complex while the platinum-195 NMR resonance at −4152 ppm indicates a mixed orientation of lone pair electrons on the sulfur donors. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)