Unique Ligand-Radical Character of an Activated Cobalt Salen Catalyst That Is Generated by Aerobic Oxidation of a Cobalt(II) Salen Complex
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https://figshare.com/articles/dataset/Unique_Ligand_Radical_Character_of_an_Activated_Cobalt_Salen_Catalyst_That_Is_Generated_by_Aerobic_Oxidation_of_a_Cobalt_II_Salen_Complex/2429707
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资源简介：
The Co(salen)(X) complex, where salen
is chiral N,N′-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediamine and X is
an external axial ligand, has been widely utilized as a versatile
catalyst. The Co(salen)(X) complex is a stable solid that has been
conventionally described as a CoIII(salen)(X) complex.
Recent theoretical calculations raised a new proposal that the Co(salen)(H2O)(SbF6) complex contains appreciable contribution
from a CoII(salen•+) electronic structure
(Kochem, A.; Kanso, H.; Baptiste, B.; Arora, H.; Philouze, C.; Jarjayes,
O.; Vezin, H.; Luneau, D.; Orio, M.; Thomas, F. Inorg. Chem. 2012, 51, 10557–10571), while
other theoretical calculations for Co(salen)(Cl) indicated a triplet
CoIII(salen) electronic structure (Kemper, S.; Hrobárik,
P.; Kaupp, M.; Schlörer, N. E. J. Am. Chem. Soc. 2009, 131, 4172–4173). However,
there have been no experimental data to evaluate these theoretical
proposals. We herein report key experimental data on the electronic
structure of the Co(salen)(X) complex (X = CF3SO3–, SbF6–, and p-MeC6H4SO3–). The X-ray crystallography shows that Co(salen)(OTf) has a square-planar
N2O2 equatorial coordination sphere with OTf
as an elongated external axial ligand. Magnetic susceptibility data
indicate that Co(salen)(OTf) complexes belong to the S = 1 spin system. 1H NMR measurements provide convincing
evidence for the CoII(salen•+)(X) character,
which is estimated to be about 40% in addition to 60% CoIII(salen)(X) character. The CH2Cl2 solution of
Co(salen)(X) shows an intense near-IR absorption, which is assigned
as overlapped transitions from a ligand-to-metal charge transfer in
CoIII(salen)(X) and a ligand-to-ligand charge transfer
in CoII(salen•+)(X). The present experimental
study establishes that the electronic structure of Co(salen)(X) contains
both CoII(salen•+)(X) and CoIII(salen)(X) character.
创建时间：
2016-02-19
