Synthesis and study of monomeric and sulfur-bridged dimeric cobalt (III) thioxanthate complexes and their relationship to sulfur-bridged iron (III) dimers

D. F. Lewis, S. J. Lippard, Jon A Zubieta

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Abstract

The synthesis of the compounds [Co(S2CSR)2(SR)]2, R = C2H5, n-C3H7, and Co(S2CSR)3, R = CH3, C2H5, n-C3H7, tert-C4H9, and C6H5CH2, is reported. The elimination of carbon disulfide from tris(ethyl thioxanthato)cobalt(III) to form tetrakis(ethyl thioxanthato)-μ-bis(ethylthio)-dicobalt(III) has been directly confirmed and is shown to be a first-order reaction. The molecular structure of the latter compound was revealed in a single-crystal X-ray diffraction study. The molecule is a centrosymmetric dimer with two bridging ethyl mercaptide ligands [distances : Co-S, 2.242 (2), 2.250 (2) Å; nonbonded Co ⋯Co, 3.321 (2) Å; angles : S-Co-S, 84.54 (5)°; Co-S-Co, 95.34 (3)°] and four terminal thioxanthate groups [Co-S distances: 2.261 (2), 2.264 (2), 2.282 (2), and 2.290 (2) Å; S-Co-S chelate ring angles: 75.68 (7)°, 76.05 (7)°]. The relationship between metal-metal bonding and the choice of stereoisomer for [M(S2CSR)2(SR)]2 complexes, M = Fe, Co, is discussed. The pmr spectra of solutions of the cobalt dimers are consistent with the structure found in the solid for the ethyl derivative. The methylenic protons attached to the bridging sulfur atoms exhibit large upfield shifts which may result from paramagnetic anisotropy effects. Voltammetric studies of the dimers indicate irreversible one-electron reduction and oxidation waves. The monomers exhibit reversible one-electron reduction waves. Electronic and selected infrared spectral absorptions are reported and assigned. A rationale is suggested for the low and varying redox potentials in nonheme proteins containing the Fe2S2 core.

Original languageEnglish (US)
Pages (from-to)1563-1575
Number of pages13
JournalJournal of the American Chemical Society
Volume94
Issue number5
StatePublished - 1972
Externally publishedYes

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Cobalt
Sulfur
Dimers
Iron
Metals
Electrons
Carbon Disulfide
Stereoisomerism
Anisotropy
Molecular Structure
X-Ray Diffraction
Oxidation-Reduction
Carbon disulfide
Protons
Ligands
Molecular structure
Monomers
Single crystals
Infrared radiation
Derivatives

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

@article{9ac63e263ce840b59937e7ecb60fc106,
title = "Synthesis and study of monomeric and sulfur-bridged dimeric cobalt (III) thioxanthate complexes and their relationship to sulfur-bridged iron (III) dimers",
abstract = "The synthesis of the compounds [Co(S2CSR)2(SR)]2, R = C2H5, n-C3H7, and Co(S2CSR)3, R = CH3, C2H5, n-C3H7, tert-C4H9, and C6H5CH2, is reported. The elimination of carbon disulfide from tris(ethyl thioxanthato)cobalt(III) to form tetrakis(ethyl thioxanthato)-μ-bis(ethylthio)-dicobalt(III) has been directly confirmed and is shown to be a first-order reaction. The molecular structure of the latter compound was revealed in a single-crystal X-ray diffraction study. The molecule is a centrosymmetric dimer with two bridging ethyl mercaptide ligands [distances : Co-S, 2.242 (2), 2.250 (2) {\AA}; nonbonded Co ⋯Co, 3.321 (2) {\AA}; angles : S-Co-S, 84.54 (5)°; Co-S-Co, 95.34 (3)°] and four terminal thioxanthate groups [Co-S distances: 2.261 (2), 2.264 (2), 2.282 (2), and 2.290 (2) {\AA}; S-Co-S chelate ring angles: 75.68 (7)°, 76.05 (7)°]. The relationship between metal-metal bonding and the choice of stereoisomer for [M(S2CSR)2(SR)]2 complexes, M = Fe, Co, is discussed. The pmr spectra of solutions of the cobalt dimers are consistent with the structure found in the solid for the ethyl derivative. The methylenic protons attached to the bridging sulfur atoms exhibit large upfield shifts which may result from paramagnetic anisotropy effects. Voltammetric studies of the dimers indicate irreversible one-electron reduction and oxidation waves. The monomers exhibit reversible one-electron reduction waves. Electronic and selected infrared spectral absorptions are reported and assigned. A rationale is suggested for the low and varying redox potentials in nonheme proteins containing the Fe2S2 core.",
author = "Lewis, {D. F.} and Lippard, {S. J.} and Zubieta, {Jon A}",
year = "1972",
language = "English (US)",
volume = "94",
pages = "1563--1575",
journal = "Journal of the American Chemical Society",
issn = "0002-7863",
publisher = "American Chemical Society",
number = "5",

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TY - JOUR

T1 - Synthesis and study of monomeric and sulfur-bridged dimeric cobalt (III) thioxanthate complexes and their relationship to sulfur-bridged iron (III) dimers

AU - Lewis, D. F.

AU - Lippard, S. J.

AU - Zubieta, Jon A

PY - 1972

Y1 - 1972

N2 - The synthesis of the compounds [Co(S2CSR)2(SR)]2, R = C2H5, n-C3H7, and Co(S2CSR)3, R = CH3, C2H5, n-C3H7, tert-C4H9, and C6H5CH2, is reported. The elimination of carbon disulfide from tris(ethyl thioxanthato)cobalt(III) to form tetrakis(ethyl thioxanthato)-μ-bis(ethylthio)-dicobalt(III) has been directly confirmed and is shown to be a first-order reaction. The molecular structure of the latter compound was revealed in a single-crystal X-ray diffraction study. The molecule is a centrosymmetric dimer with two bridging ethyl mercaptide ligands [distances : Co-S, 2.242 (2), 2.250 (2) Å; nonbonded Co ⋯Co, 3.321 (2) Å; angles : S-Co-S, 84.54 (5)°; Co-S-Co, 95.34 (3)°] and four terminal thioxanthate groups [Co-S distances: 2.261 (2), 2.264 (2), 2.282 (2), and 2.290 (2) Å; S-Co-S chelate ring angles: 75.68 (7)°, 76.05 (7)°]. The relationship between metal-metal bonding and the choice of stereoisomer for [M(S2CSR)2(SR)]2 complexes, M = Fe, Co, is discussed. The pmr spectra of solutions of the cobalt dimers are consistent with the structure found in the solid for the ethyl derivative. The methylenic protons attached to the bridging sulfur atoms exhibit large upfield shifts which may result from paramagnetic anisotropy effects. Voltammetric studies of the dimers indicate irreversible one-electron reduction and oxidation waves. The monomers exhibit reversible one-electron reduction waves. Electronic and selected infrared spectral absorptions are reported and assigned. A rationale is suggested for the low and varying redox potentials in nonheme proteins containing the Fe2S2 core.

AB - The synthesis of the compounds [Co(S2CSR)2(SR)]2, R = C2H5, n-C3H7, and Co(S2CSR)3, R = CH3, C2H5, n-C3H7, tert-C4H9, and C6H5CH2, is reported. The elimination of carbon disulfide from tris(ethyl thioxanthato)cobalt(III) to form tetrakis(ethyl thioxanthato)-μ-bis(ethylthio)-dicobalt(III) has been directly confirmed and is shown to be a first-order reaction. The molecular structure of the latter compound was revealed in a single-crystal X-ray diffraction study. The molecule is a centrosymmetric dimer with two bridging ethyl mercaptide ligands [distances : Co-S, 2.242 (2), 2.250 (2) Å; nonbonded Co ⋯Co, 3.321 (2) Å; angles : S-Co-S, 84.54 (5)°; Co-S-Co, 95.34 (3)°] and four terminal thioxanthate groups [Co-S distances: 2.261 (2), 2.264 (2), 2.282 (2), and 2.290 (2) Å; S-Co-S chelate ring angles: 75.68 (7)°, 76.05 (7)°]. The relationship between metal-metal bonding and the choice of stereoisomer for [M(S2CSR)2(SR)]2 complexes, M = Fe, Co, is discussed. The pmr spectra of solutions of the cobalt dimers are consistent with the structure found in the solid for the ethyl derivative. The methylenic protons attached to the bridging sulfur atoms exhibit large upfield shifts which may result from paramagnetic anisotropy effects. Voltammetric studies of the dimers indicate irreversible one-electron reduction and oxidation waves. The monomers exhibit reversible one-electron reduction waves. Electronic and selected infrared spectral absorptions are reported and assigned. A rationale is suggested for the low and varying redox potentials in nonheme proteins containing the Fe2S2 core.

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