Molecular and electronic structures of tetrahedral complexes of nickel and cobalt containing N,N′-disubstituted, bulky o-diiminobenzosemiquinonate(1-) π-radical ligands
Molecular and electronic structures of tetrahedral complexes of nickel and cobalt containing N,N′-disubstituted, bulky o-diiminobenzosemiquinonate(1-) π-radical ligands
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DOI：
10.1021/ic060242l
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发表时间：
2006-08-07
影响因子：
4.6
通讯作者：
Wieghardt, Karl
中科院分区：
文献类型：
--
作者：
Chlopek, Krzysztof;Bothe, Eberhard;Wieghardt, Karl
2当量的大体积配体N，N ′-双（3，5-二叔丁基苯基）-1，2-苯二胺，H-2 [L-3（PDI）]，过量三乙胺，和1当量M（CH3CO2）（2）中心点4H（2）O（M = Ni，Co）在空气存在下的CH_3CN/CH_2Cl_2溶液中生成紫黑色晶体[Ni-II（L-3（ISQ））（2）] CH_3CN（1）或紫色晶体[Co（L-3）（2）]（三）、以Pd（CH_3CO_2）（2）为原料，得到了[Pd-II（L-3（ISQ））（2）]中心点CH_3CN（2）的蓝绿色晶体。单晶X射线晶体学显示，1和3含有（假）四面体中性分子[M（L-3）（2）]（M）Ni，Co），而在2中存在接近正方形平面的中性分子[Pd-II（L-3（ISQ））（2）]。依赖于温度的磁化率测量确定1和2是抗磁性的（S）0），而3是顺磁性的（S）3/2基态。结果表明，1含有两个π自由基苯并半醌（1-）型一元阴离子（（L-3（ISQ））（1-中心点），S-rad = 1/2）和一个中心Ni（II）离子（d（8）; S = 1），它们反铁磁耦合，得到所观察到的S-t = 0基态.这一结果已被1的破缺对称DFT计算所证实。相比之下，3的S-t = 3/2基态更难理解：可以调用两个共振结构[Co-III（L-3（ISQ））（L-3（PDI））][Co-II（L-3（PDI））（L-3（IBQ））]（对于含有具有两个反铁磁耦合的d-自由基配体的S（Co）3/2的四面体[CoII（3LISQ）2]，预期S = 1/2）。配合物2是抗磁性的（S = 0），含有一个Pd-II离子（d（8），在几乎正方形的平面配体场中S-Pd = 0）和两个反铁磁耦合的配体自由基（S-rad = 1/2）。研究了化合物1、2和3的电化学和光谱电化学，建立了[M（L）（2）]（z）（z = 2+，1+，0，1-，2-）的电子转移系列。所有的氧化和还原都是以配体为中心的。
The reaction of 2 equiv of the bulky ligand N,N'-bis(3,5-di-tert-butylphenyl)-1,2-phenylenediamine, H-2[L-3(PDI)], excess triethylamine, and 1 equiv of M(CH3CO2)(2)center dot 4H(2)O (M = Ni, Co) in the presence of air in CH3CN/CH2Cl2 solution yields violet-black crystals of [Ni-II(L-3(ISQ))(2)] CH3CN (1) or violet crystals of [Co(L-3)(2)] (3). By using Pd(CH3CO2)(2) as starting material, green-blue crystals of [Pd-II(L-3(ISQ))(2)]center dot CH3CN (2) were obtained. Single-crystal X-ray crystallography revealed that 1 and 3 contain ( pseudo) tetrahedral neutral molecules [M(L-3)(2)] ( M) Ni, Co) whereas in 2 nearly square planar, neutral molecules [Pd-II(L-3(ISQ))(2)] are present. Temperature-dependent susceptibility measurements established that 1 and 2 are diamagnetic ( S) 0) whereas 3 is paramagnetic with an S) 3/ 2 ground state. It is shown that 1 contains two pi radical benzosemiquinonate(1-)-type monoanions, ((L-3(ISQ))(1-center dot), S-rad = 1/2), and a central Ni(II) ion (d(8); S = 1) which are antiferromagnetically coupled yielding the observed S-t = 0 ground state. This result has been confirmed by broken symmetry DFT calculations of 1. In contrast, the S-t = 3/2 ground state of 3 is more difficult to understand: the two resonance structures [Co-III(L-3(ISQ))(L-3(PDI))] [Co-II(L-3(PDI))(L-3(IBQ))] might be invoked ( for tetrahedral [ CoII( 3LISQ) 2] containing an S Co) 3/ 2 with two antiferromagnetically coupled d- radical ligands an S-t = 1/2 is anticipated). Complex 2 is diamagnetic (S = 0) containing a Pd-II ion (d(8), S-Pd = 0 in an almost square planar ligand field) and two antiferromagnetically coupled ligand radicals (S-rad = 1/2). The electrochemistry and spectroelectrochemistry of 1, 2, and 3 have been studied, and electron-transfer series comprising the species [M(L)(2)](z) (z = 2+, 1+, 0, 1-, 2-) have been established. All oxidations and reductions are ligand centered.