Bill Eckhard, Bothe Eberhard, Chaudhuri Phalguni, Chlopek Krzysztof, Herebian Diran, Kokatam Swarnalatha, Ray Kallol, Weyhermüller Thomas, Neese Frank, Wieghardt Karl
Max-Planck-Institut für Bioanorganische Chemie, Stiftstrasse 34-36, 45470 Mülheim an der Ruhr, Germany.
Chemistry. 2004 Dec 17;11(1):204-24. doi: 10.1002/chem.200400850.
The bidentate ligands N-phenyl-o-phenylenediamine, H(2)((2)L(N)IP), or its analogue 2-(2-trifluoromethyl)anilino-4,6-di-tert-butylphenol, ((4)L(N)IP), react with [Co(II)(CH(3)CO(2))(2)]4H(2)O and triethylamine in acetonitrile in the presence of air yielding the square-planar, four-coordinate species [Co((2)L(N))(2)] (1) and [Co((4)L(O))(2)] (4) with an S=1/2 ground state. The corresponding nickel complexes [Ni((4)L(O))(2)] (8) and its cobaltocene reduced form [Co(III)(Cp)(2)][Ni((4)L(O))(2)] (9) have also been synthesized. The five-coordinate species [Co((2)L(N))(2)(tBu-py)] (2) (S=1/2) and its one-electron oxidized forms Co((2)L(N))(2)(tBu-py) (2 a) or [Co((2)L(N))(2)I] (3) with diamagnetic ground states (S=0) have been prepared, as has the species [Co((4)L(O))(2)(CH(2)CN)] (7). The one-electron reduced form of 4, namely [Co(Cp)(2)][Co((4)L(O))(2)] (5) has been generated through the reduction of 4 with [Co(Cp)(2)]. Complexes 1, 2, 2 a, 3, 4, 5, 7, 8, and 9 have been characterized by X-ray crystallography (100 K). The ligands are non-innocent and may exist as catecholate-like dianions ((2)L(N)IP)(2-), ((4)L(N)IP)(2-) or pi-radical semiquinonate monoanions ((2)L(N)ISQ)() (-), ((4)L(N)ISQ)() (-) or as neutral benzoquinones ((2) L(N)IBQ)(0), ((4) L(N)IBQ)(0); the spectroscopic oxidation states of the central metal ions vary accordingly. Electronic absorption, magnetic circular dichroism, and EPR spectroscopy, as well as variable temperature magnetic susceptibility measurements have been used to experimentally determine the electronic structures of these complexes. Density functional theoretical (DFT) and correlated ab initio calculation have been performed on the neutral and monoanionic species Co((1)L(N))(2) in order to understand the structural and spectroscopic properties of complexes. It is shown that the corresponding nickel complexes 8 and 9 contain a low-spin nickel(II) ion regardless of the oxidation level of the ligand, whereas for the corresponding cobalt complexes the situation is more complicated. Spectroscopic oxidation states describing a d(6) (Co(III)) or d(7) (Co(II)) electron configuration cannot be unambiguously assigned.
双齿配体N-苯基邻苯二胺（H₂((2)L(N)IP)）或其类似物2-(2-三氟甲基)苯胺基-4,6-二叔丁基苯酚（((4)L(N)IP)），在空气中于乙腈中与[Co(II)(CH₃CO₂)₂]·4H₂O和三乙胺反应，生成具有S = 1/2基态的平面正方形四配位物种[Co((2)L(N))₂]（1）和[Co((4)L(O))₂]（4）。相应的镍配合物[Ni((4)L(O))₂]（8）及其钴茂还原形式[Co(III)(Cp)₂][Ni((4)L(O))₂]（9）也已合成。已制备出五配位物种[Co((2)L(N))₂(tBu-py)]（2）（S = 1/2）及其单电子氧化形式Co((2)L(N))₂(tBu-py)（2 a）或具有抗磁基态（S = 0）的[Co((2)L(N))₂I]（3），以及物种[Co((4)L(O))₂(CH₂CN)]（7）。通过用[Co(Cp)₂]还原4生成了4的单电子还原形式，即[Co(Cp)₂][Co((4)L(O))₂]（5）。配合物1、2、2 a、3、4、5、7、8和9已通过X射线晶体学（100 K）进行了表征。这些配体并非单纯的配体，可能以类似邻苯二酚的二价阴离子（(2)L(N)IP）²⁻、(4)L(N)IP）²⁻形式存在，或π-自由基半醌单阴离子（(2)L(N)ISQ）⁎⁻、(4)L(N)ISQ）⁎⁻形式存在，也可能以中性苯醌（(2) L(N)IBQ）⁰、(4) L(N)IBQ）⁰形式存在；中心金属离子的光谱氧化态也相应变化。已使用电子吸收光谱、磁圆二色光谱和电子顺磁共振光谱，以及变温磁化率测量来实验确定这些配合物的电子结构。为了理解配合物的结构和光谱性质，对中性和单阴离子物种[Co((1)L(N))₂]⁰,⁻进行了密度泛函理论（DFT）和相关的从头算计算。结果表明，相应的镍配合物8和9无论配体的氧化水平如何都含有低自旋镍(II)离子，而对于相应的钴配合物情况则更为复杂。描述d⁶（Co(III)）或d⁷（Co(II)）电子构型的光谱氧化态无法明确指定。
