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Lookup NU author(s): Emeritus Prof Alfred Sykes
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A series of mu(3)-sulfido Re-Re bonded octahedral hexarhenium(III) clusters having mixed chloride-pyridine (py) or -4-cyanopyridine (cpy) terminal ligands, [Bu4N](2)[trans-{Re6S8Cl4(py)(2)}] (Bu4N+ = tetra-n-butylammonium cation) (1a), [Bu4N](2)[cis-{Re6S8Cl4(py)(2)}] (1b), [Bu4N](2)[trans-{Re6S8Cl4(cpy)(2)}] (2a), [Bu4N]2[cis-{Re(6)S(8)Cl4-(cpy)(2)}] (2b), and [Bu4N] [mer-{Re6S8Cl3(py)(3)}] (3), and their one-electron-oxidized (Re5ReIV)-Re-III species, [Bu4N]-[trans-{Re6S8Cl4(py)(2)}] (1a'), [Bu4N][trans-{Re6S8Cl4(cpy)(2)}] (2a'), and mer-[Re6S8Cl4(py)(3)] (3'), have been prepared and characterized by several physical methods. X-ray crystallographic studies for 1a, 2a, and 3 showed that the Re6S8 core structures are not significantly affected by the type and number of pyridyl ligands. The mixed valent cluster 1a' is of a structurally delocalized type, structural parameters being very similar to those of 1a. Cyclic voltammograms in acetonitrile showed that there is no distinct difference in the redox potentials (Re-6(III)/(Re5ReIV)-Re-III) between the cis and the corresponding trans isomers. Both la and Ib show a reversible redox wave at 0.77 V vs Ag/AgCl. Redox potentials are more positive for 2a and 2b (0.83 V) and 3 (0.97 V). Clusters 2a and 2b show two-step ligand-centered redox waves at -1.19 and -1.28 V, and -1.18 and -1.29 V, respectively. Temperature-dependent magnetic susceptibility measurements have revealed that 1a' and 3' have an S = 1/2 ground state. The electron self-exchange rate constant for the reaction of 2a with 2a' in dichloromethane as obtained by H-1 NMR line-broadening method is 1.2 x 10(9) M-1 s(-1) (298.2 K) with Delta H double dagger = 30.2 +/- 2.1 kJ mol(-1) and Delta S double dagger = 30 +/- 8 J mol(-1) K-1. It has been suggested that the previously reported protonated species [Re6S7(SH)Cl-6](3-) would actually be a one-electron-oxidized [Re6S8Cl6](3-). Crystal data: [Bu4N](2)[trans-{Re6S8Cl4(py)(2)}] (1a), monoclinic, space group C2/c, a = 24.693(8) Angstrom, b = 19.494(4) Angstrom, c = 18.592(4) Angstrom, beta = 115.76(2)degrees, Z = 4; [Bu4N](2)[trans-(Re6S8Cl4(cpy)(2)}] (2a), orthorhombic, space group Cmca, a = 19.304(3) Angstrom, b = 17.894(7) Angstrom, c = 18.773(4) Angstrom, Z = 4; [Bu4N] [mer-{Re6S8Cl3(py)3)] (3), monoclinic, space group P2(1)/n, a = 16.156(5) Angstrom, b = 19.760(5) Angstrom, c = 18.895(4) Angstrom, beta = 108.94(2)degrees, Z = 4; [Bu4N][trans-{Re6S8Cl4(py)(2)}] (1a'), monoclinic, space group C2/c, a = 20.524(5) Angstrom, b = 13.794(4) Angstrom, c = 16.399(4) Angstrom, beta = 109.72(2)degrees, Z = 4.
Author(s): Yoshimura T, Umakoshi K, Sasaki Y, Sykes AG
Publication type: Article
Publication status: Published
Journal: Inorganic Chemistry
Year: 1999
Volume: 38
Issue: 24
Pages: 5557-5564
Print publication date: 01/11/1999
ISSN (print): 0020-1669
ISSN (electronic): 1520-510X
Publisher: American Chemical Society
URL: http://dx.doi.org/10.1021/ic9907922
DOI: 10.1021/ic9907922
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