Products of the reactions of [Re2X8](2-) with 3,6-dithiaoctane (dto). Preparation and crystal structures of Re2Cl5(dto)(2), Re2Br5(dto)(2), and (n-Bu4N)(2)Re-2(NCS)(8)center dot dto

The reactions of the quadruply bonded complexes (n-Bu4N)(2)Re2X8 (X=Cl, Br) with excess 3,6-dithiaoctane (CH3CH2SCH2CH2SCH2CH3 or dto) under forcing c onditions lead to the compounds Re2Cl5(dto)(2) (1) and Re2Br5(dto)(2) (2) w ith Re-Re triple bonds. X-ray crystallographic studies of compounds 1 and 2 reveal a common staggered, unsymmetrical molecular geometry with both dto ligands chelated to the same metal atom. This Re atom is also bonded to a s ingle axial halide ligand, while the other four halides surround the second Re atom. In contrast to the only previous example of this type of dirheniu m compound, Re2Cl5(dithiahexane)(2), there is no sharing of axial chloride ligands between molecules in the crystal lattices of 1 and 2. The Re-Re bon d distances are 2.2772(8) and 2.2826(6) Angstrom in 1 and 2, respectively. Magnetic measurements, cyclic voltammetry, and IR, Vis and ESR spectra of 1 and 2 are reported. Addition of dto to a solution of (n-Bu4N)(2)Re-2(NCS)( 8) leads to the formation of (n-Bu4N)(2)Re-2(NCS)(8)dto (3). Crystallograph ic studies show 3 to consist in the solid state of chains of [Re-2(NCS)(8)] (2-) units linked together by dto molecules with each dto sulfur atom weakl y coordinated to axial sites on Re atoms of different anions. The Re-Re qua druple bond distance in 3 is 2.2854(3) Angstrom. (C) 2001 Elsevier Science Ltd. All rights reserved.