ELSEVIER Inorganica Chimica Acta 234 (1995) 35-45 Crown thioether complexes of trivalent transition metal ions. The crystal structure of [Cr(18S6)C13] Gregory J. Grant a'*, Karen E. Rogers a, William N. Setzer u, Donald G. VanDerveer c a Department of Chemistry, The University of Tennessee at Chattanooga, Chattanooga, TN 37403, USA b Department of Chemistry, The University of Alabama in Huntsville, Huntsville, AL 35899, USA c School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332, USA Received 11 August 1994; revised 15 December 1994 Abstract The structure of the macrocyclic complex, [Cr(18S6)C13] (18S6 = 1,4,7,10,13,16-hexathiacyclooctadecane), has been determined by single-crystal X-ray diffraction, the first Cr(III)-thioether coordination complex to be structurally characterized. An octahedral environment of three sulfur atoms and three chlorine atoms around the Cr(III) center is observed in the complex, and the stereoisomer obtained in our case is the one in which only three adjacent sulfur atoms in the 18S6 ligand are bonded to the CrCI3 moiety. This is also the first reported structure of this atypical coordination mode for the 18S6 ligand which typically coordinates in hexadentate fashion or as a bridging ligand. The syntheses, characterization, and electronic spectra of a series of eleven additional thioether complexes of Cr(III) are described. All twelve Cr complexes have the general formula CrLCI3 and potentially tetra-, penta- and hexadentate thioether ligands all function as tridentate ligands coordinating to a single metal center. The electronic spectra for the Cr complexes are all similar and enable ligand field parameters readily to be calculated. The thioethers function as weak field ligands, and there is a substantial reordering in their spectrochemical series when compared to the series obtained with softer metal ions such as Ni(II) or Fe(II). In addition, the synthesis and characterization of two novel V(III) complexes with the general formula VLCI3 where L = 1,4,7-trithiacyclononane (9S3) or 1,4,7-trithiacyclodecane (10S3) are described. These are the first two reported examples of thioether complexes of vanadium(IlI). The reaction between 9S3 and the anion [Re2CIs] 2- has also been investigated. Keywords: Crown thioether complexes; Macrocycle complexes; Chromium complexes; Vanadium complexes; Ligand field spectra; Crystal structures 1. Introduction During the past few years there has been a remarkable increase in research activity of the coordination chem- istry of thioether ligands, especially research dealing with the nine-membered ring trithioether, 1,4,7-tri- thiacyclononane (9S3). Several excellent review articles dealing with the coordination chemistry of 9S3 and ~' Synthesis and Complexation Studies of Mesocyclic and Macro- cyclic Polythioethers, XII. For Part X, see W.N. Setzer, Y. Tang, G.J. Grant and D.G. VanDerveer, lnorg. Chem., 31 (1992) 1116. For Part XI, see G.J. Grant, S.M. Isaac, W.N. Setzer and D.G. VanDerveer, Inorg. Chem., 32 (1993) 4284. This work was presented in part at the joint 42rid Southeastern Regional Meeting/46th Southwestern Regional Meeting of the American Chemical Society, New Orleans, LA, USA, 5-7 Dec. 1990, Paper No. 295, and the 201st National Meeting of the American Chemical Society, Atlanta, GA, USA, 14--19 Apr. 1991, Paper No. 140. * Corresponding author. 0020-1693/95/$09.50 © 1995 Elsevier Science S.A. All rights reserved SSDI 0020-1693(95)04462-1 related thioether ligand systems have appeared [1--4]. Because of the ability of thioether ligands to stabilize lower oxidation states through their rr-acidity, most past research efforts have focused on thioether complexation with soft or borderline metal ions. In fact, the majority of thioether coordination chemistry with first row tran- sition metal ions has dealt with the divalent state. The preparation of bis complexes of 9S3 with trivalent, first row transition metals has been limited to chromium(III), cobalt(Ill) and iron(Ill) [5-7]. Of these three, only the cobalt complex is easily synthesized and stable [8]. The perchlorate salt of the chromium(Ill) complex explodes while the iron(III) complex is unstable with respect to air oxidation and forms only under conditions of high acidity [7,9]. Also, non-homoleptic 9S3 complexes with Fe(III) ([Fe(9S3)C13]) and Cr(III) ([Cr(9S3)C13] and [Cr(9S3)(triflate)3]) have been reported. We undertook the complexation of 9S3 and a variety of additional