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Title: Synthesis and reactivity of cobalt complexes derived from tris(2-pyridylthio)methane ligand: Structural characterization of cobalt(III) complexes containing cobalt–carbon bond
Authors: Halder, Partha
Paine, Tapan Kanti
Keywords: Organometallic compounds
Organocobalt complexes
Metal–carbon bond
Solid state structure
Issue Date: Sep-2011
Publisher: NISCAIR-CSIR, India
Abstract: The synthesis, characterization and reactivity of a cobalt(II) complex, [(HL<sup>1</sup>)Co<sup>II</sup>(PyS)](ClO<sub>4</sub>) (<b style="">1)</b> (where HL<sup>1</sup> = tris(2-pyridylthio)methane and PyS = monoanionic pyridine-2-thiolate) are discussed. Complex (<b style="">1</b>) reacts with molecular oxygen to yield a mononuclear low-spin cobalt(III) complex, [(L<sup>1</sup>)Co<sup>III</sup>(PyS)](ClO<sub>4</sub>) (<b style="">2</b>). On the other hand, treatment of (<b style="">1</b>) with a protic acid (pyridinium perchlorate) followed by a base (triethylamine) and dioxygen forms an isomeric cobalt(III) complex, [(L<sup>2</sup>)Co<sup>III</sup>(PyS)](ClO<sub>4</sub>) (<b style="">3</b>) (L<sup>2</sup> = 1-[bis(2-pyridylthio)methyl]pyridine-2-thione). Ligand HL<sup>1</sup> (in <b style="">1</b>) rearranges to L<sup>2</sup> (in <b style="">3</b>) during the reaction as a result of C–S bond cleavage and subsequent C–N bond formation. X-ray crystal structures of both (<b style="">2</b>) and (<b style="">3</b>) reveal a distorted octahedral coordination geometry at cobalt(III) center with a strong cobalt–carbon bonding interaction. A four-coordinate distorted tetrahedral cobalt(II) complex, [Co<sup>II</sup>(PySH)<sub>4</sub>](ClO<sub>4</sub>)<sub>2</sub> (<b style="">4</b>) is formed via C–S bond cleavage of HL<sup>1</sup> in the reaction of (<b style="">1</b>) with an excess amount of pyridinium perchlorate. The electronic structure of (<b style="">2</b>) as established by DFT calculation suggests a delocalized LUMO with significant contribution from the metal ion. The organocobalt(III) complex converts to an air-stable organocobalt(II) complex (<b style="">2<sup>red</sup></b>) upon one-electron reduction.
Description: 1394-1402
ISSN: 0975-0975(Online); 0376-4710(Print)
Appears in Collections:IJC-A Vol.50A(09-10) [September-October 2011]

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