Synthesis and reactivity of cobalt complexes derived from tris(2-pyridylthio)methane ligand: Structural characterization of cobalt(III) complexes containing cobalt–carbon bond
1394-1402The synthesis, characterization and reactivity of a cobalt(II) complex,
[(HL1)CoII(PyS)](ClO4) (1) (where
HL1 = tris(2-pyridylthio)methane and PyS = monoanionic
pyridine-2-thiolate) are discussed. Complex (1) reacts with molecular oxygen to yield a mononuclear low-spin
cobalt(III) complex, [(L1)CoIII(PyS)](ClO4) (2). On the other hand, treatment of (1) with a protic acid (pyridinium
perchlorate) followed by a base (triethylamine) and dioxygen
forms an isomeric cobalt(III) complex, [(L2)CoIII(PyS)](ClO4)
(3) (L2 =
1-[bis(2-pyridylthio)methyl]pyridine-2-thione). Ligand HL1 (in 1)
rearranges to L2 (in 3)
during the reaction as a result of C–S bond cleavage and subsequent C–N bond
formation. X-ray crystal structures of both (2) and (3) 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, [CoII(PySH)4](ClO4)2
(4) is formed via C–S bond cleavage
of HL1 in the reaction of (1)
with an excess amount of pyridinium perchlorate. The electronic structure of (2) 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 (2red) upon
one-electron reduction