Polyhedron 20 (2001) 3333 – 3342 Heteroleptic platinum(II) complexes of macrocyclic thioethers and halides: the crystal structures of [Pt(9S3)Cl 2 ], [Pt(9S3)Br 2 ], and [Pt(9S3)I 2 ] Gregory J. Grant a, *, Christopher G. Brandow a , David F. Galas a , Jaime P. Davis a , William T. Pennington b , Edward J. Valente c , Jeffrey D. Zubkowski d a Department of Chemistry, The Uniersity of Tennessee at Chattanooga, Department 2252, 615 McCallie Aenue, Chattanooga, TN 37403 -2598, USA b Department of Chemistry, Clemson Uniersity, Clemson, SC 29634, USA c Department of Chemistry, Mississippi College, Clinton, MS 39058, USA d Department of Chemistry, Jackson State Uniersity, Jackson, MS 39217, USA Received 29 May 2001; accepted 24 September 2001 Abstract The synthesis, spectroscopic, and crystal structures of three heteroleptic thioether/halide platinum(II) (Pt(II)) complexes of the general formula [Pt(9S3)X 2 ] (9S3 =1,4,7-trithiacyclononane, X =Cl - , Br - ,I - ) are presented. All three 9S3/dihalo complexes form very similar structures in which the Pt(II) center is surrounded by a cis arrangement of two halides and two sulfur atoms from the 9S3 ligand. The third sulfur from the 9S3 forms a long distance interaction with the Pt center resulting in an elongated square pyramidal structure with a S 2 X 2 +S 1 coordination geometry. The distances between the Pt(II) center and axial sulfur shorten with larger halide ions (Cl - =3.260(3) A  Br - =3.243(2) A  I - =3.207(2) A  ). These distances are consistent with the halides functioning as  donor ligands, and their PtS axial distances fall intermediate between Pt(II) thioether complexes involving  acceptor and  donor ligands. The 195 Pt NMR chemical shift values follow a similar trend with an increased shielding of the platinum ion with larger halide ions. The 9S3 ligand is fluxional in all of these complexes, producing a single carbon resonance. Additionally, a related series of homoleptic crown thioether complexes have been studied using 195 Pt NMR, and there is a strong correlation between the chemical shift and complex structure. Homoleptic crown thioethers show the anticipated upfield chemical shifts with increasing number of coordinated sulfurs. Complexes containing four coordinated sulfur donors have chemical shifts that fall in the range of -4000 to -4800 ppm while a value near -5900 ppm is indicative of five coordinated sulfurs. However, for S 4 crown thioether complexes, differences in the stereochemical orientation of lone pair electrons on the sulfur donors can greatly influence the observed 195 Pt NMR chemical shifts, often by several hundred ppm. © 2001 Elsevier Science Ltd. All rights reserved. Keywords: Thioether complexes; Platinum complexes; Trithiacyclononane; Platinum nuclear magnetic resonance; Crystal structures; Crown thioethers www.elsevier.com/locate/poly 1. Introduction Research into the coordination and organometallic chemistry of crown thioether ligands, such as 1,4,7- trithiacyclononane (9S3), has experienced a phenome- nal growth during the past decade and work continues to progress with examination of complexes formed by both transition metal and main group metal ions [1–5]. Platinum group metal complexes of these ligands have been one particularly active area of focus [6–13]. The complexes are quite stable due to the soft thioether ligand coordinating to the soft metal center, and a further impetus for this research is the unusual proper- ties, spectroscopic and electrochemical properties, dis- played by the platinum(II) (Pt(II)) crown thioether complexes including d – d electronic transitions near 435 * Corresponding author. Tel.: +1-423-755-4143; fax: +1-423-755- 5234. E-mail address: greg-grant@utc.edu (G.J. Grant). 0277-5387/01/$ - see front matter © 2001 Elsevier Science Ltd. All rights reserved. PII:S0277-5387(01)00953-6