ELSEVIER Inorganica Chimica Acta 229 (1995) 241-246 Preparation and characterization of dirhenium complex anions of the type [Re2C17(dithioether)]- with Re-Re quadruple bonds * Bruce J. Heyen, J. Gregory Jennings, Gregory L. Powell * Department of Chemistry, Abilene Christian University, Abilene, TX 79699, USA Received 22 June 1994; revised 5 September 1994 Abstract Two dirhenate(III) anions containing dithioether ligands and Re-Re quadruple bonds have been synthesized and characterized by X-ray crystallography. Under mild reaction conditions, both 3,6-dithiaoctane (CH3CH2SCH2CH2SCH2CH3 or dto) and 2,5- dithiahexane (CH3SCH2CH2SCH 3 or dth) displace a single chloride ligand from [Re2CIs] 2- to yield [Re2Cl7(dto)]- and [Re2C17(dth)]- , respectively. The tetra-n-butylammonium (Bu4N) salts of these complex ions have been isolated and found to react with additional dithioether to produce the unsymmetrical compounds Re2Cls(dto)2 and Re2Cls(dth)2 with Re-Re triple bonds. The complex (Bu4N)[Re2C17(dto)] crystallizes in the triclinic space group Pi with a = 11.299(3), b = 11.552(4), c = 14.654(4) /~, a = 108.19(2), /3= 104.07(2), 3,=88.65(3) ° and Z=2, while (Bu4N)[Re2Cl7(dth)] crystallizes in the monoclinic space group P21 with a=10.361(2), b=15.567(4), c=11.663(3) /~, /3=117.01(2) ° and Z=2. The Re-Re bond distances are 2.248(1) and 2.257(1) ~ for the dto and dth complexes, respectively. Keywords: Crystal structures; Rhenium complexes; Quadruple bond complexes; Dithioether ligand complexes; Dinuclear complexes I. Introduction The first example of a compound containing a metal-metal triple bond was synthesized many years ago by the prolonged heating of a mixture of the [Re2CIs] 2- anion with an excess of 2,5-dithiahexane (CHaSCH2CH2SCH3 or dth) [1,2]. This compound, Re2Cls(dth)2, possesses an unusual structure (repre- sented by I) that consists of four chloride ,~--~S ~." CI \/ /c, Cl Re Re \ f s/',c' I k....../ ct I ligands coordinated to one Re atom, a single axial chloride ligand and two dth ligands coordinated to the other Re atom, and a staggered rotational conformation about the central Re2 unit [3]. Only recently, as a result of our investigations into the reactivity of [Re2Xs] 2- This paper is dedicated to Professor F.A. Cotton on the occasion of his 65th birthday. * Corresponding author. (X=C1 or Br) with 3,6-dithiaoctane (CH3CH2SCH2- CH2SCH2CH 3 or dto), have additional examples of this type of molecule been isolated, namely Re2C15(dto)2 and Re2Brs(dto)2 [4]. At the same time that Re2C15(dth)2 was first prepared, several other dirhenium complexes containing dth were synthesized but not structurally characterized [2]. Their proposed molecular formulas are Re2Cl6(dth)2, Re2Br6(dth)2 and Re2Bra(dth)2. In our efforts to prepare the dto analogs of these compounds, we have instead isolated the dirhenium monoanion [Re2Clv(dto)]- with only one chelating dithioether ligand. Under similar conditions, we were also able to prepare [Re2C17(dth)]-. These anions react with additional dithioether (SS) to yield the neutral compounds Re2C15(SS)2 with structures as noted above, and are therefore proposed to be intermediates in the formation of triply bonded com- pounds from quadruply bonded starting materials. Recently, several monoanionic complexes of the type [Re2CITL]-, where L is a large monodentate tertiary phosphine ligand, have been prepared and structurally characterized [5-7]. These react with additional phos- phine to give the neutral compounds Re2CI6L 2 with eclipsed conformations, quadruple Re-Re bonds, and trans phosphine ligands coordinated to different Re atoms [5,8]. The structures of the [Re2CI7(SS)]- com- 0020-1693/95/$09.50 © 1995 Elsevier Science S.A. All rights reserved SSDI 0020-1693(94)04250-Y