Synthesis and Molecular and Electronic Structures of Reduced Bis(imino)pyridine Cobalt Dinitrogen Complexes: Ligand versus Metal Reduction
Synthesis and Molecular and Electronic Structures of Reduced Bis(imino)pyridine Cobalt Dinitrogen Complexes: Ligand versus Metal Reduction
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DOI：
10.1021/ja908955t
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发表时间：
2010-02-10
影响因子：
15
通讯作者：
Chirik, Paul J.
中科院分区：
文献类型：
--
作者：
Bowman, Amanda C.;Milsmann, Carsten;Chirik, Paul J.
芳基取代的双（亚氨基）吡啶钴二卤化物配合物（（PDI）-P-Ar）CoCl 2和（（iPr）BPDI）CoCl 2（（PDI）-P-Ar = 2，6-（2，6-R-2-C6H3N=CMe）（2）C5H3N（R = Pr-1，Et，Me）;（BPDI）-B-iPr = 2，6-（二、6-Pr-i（2）-C6 H3 N =CPh）（2）C5 H3 N）在N2气氛下反应，得到相应的中性钴二氮配合物（（PDI）-P-Ar）CoN 2和（（BPDI）-B-iPr）CoN2。对这些化合物的磁性测量建立了双重基态。通过X射线衍射表征了两个实例（（PDI）-P-iPr）CoN 2和（（BPDI）-B-iPr）CoN 2，并且表现出与单电子螯合物还原和Co（I）氧化态一致的测量参数。因此，（（PDI）-P-iPr）CoN 2在23 ℃下的甲苯溶液EPR光谱显示出各向同性信号，g值为2.003，与1 = 7/2 Co-59中心的超精细耦合常数为8 × 10（-4）cm（-1），表明主要是基于双（亚氨基）吡啶的SOMO。通过在THF中用Na[C10 H8]处理来完成（（PDI）-P-iPr）CoN 2的另外的单电子还原，并产生钴二氮阴离子[（（PDI）-P-iPr）CoN 2]（-），对一系列阳离子、中性和阴离子双（亚氨基）吡啶钴二氮化合物的DFT计算在每种情况下建立了Co（I）中心，并且在每个顺序的单电子还原步骤中建立了螯合物中心的还原。频率计算成功地再现了实验确定的N-N红外伸缩频率，并验证了计算方法。在更广泛的背景下，双（亚氨基）吡啶碱金属化学和金属d电子构型的影响，对封闭壳层与三重态双自由基二阴离子的偏好，减少钴二氮配合物的电子结构进行评估。
Sodium amalgam reduction of the aryl-substituted bis(imino)pyridine cobalt dihalide complexes ((PDI)-P-Ar)CoCl2 and ((iPr) BPDI)CoCl2 ((PDI)-P-Ar = 2,6-(2,6-R-2-C6H3N=CMe)(2)C5H3N (R = Pr-i, Et, Me); (BPDI)-B-iPr = 2,6-(2,6-Pr-i(2)-C6H3N=CPh)(2)C5H3N) in the presence of an N-2 atmosphere furnished the corresponding neutral cobalt dinitrogen complexes ((PDI)-P-Ar)CoN2 and ((BPDI)-B-iPr)CoN2. Magnetic measurements on these compounds establish doublet ground states. Two examples, ((PDI)-P-iPr)CoN2 and ((BPDI)-B-iPr)CoN2, were characterized by X-ray diffraction and exhibit metrical parameters consistent with one-electron chelate reduction and a Co(I) oxidation state. Accordingly, the toluene solution EPR spectrum of ((PDI)-P-iPr)CoN2 at 23 degrees C exhibits an isotropic signal with a g value of 2.003 and hyperfine coupling constant of 8 x 10(-4) cm(-1) to the l = 7/2 Co-59 center, suggesting a principally bis(imino)pyridine-based SOMO. Additional one-electron reduction of ((PDI)-P-iPr)CoN2 was accomplished by treatment with Na[C10H8] in THF and yielded the cobalt dinitrogen anion [((PDI)-P-iPr)CoN2](-), DFT calculations on the series of cationic, neutral, and anionic bis(imino)pyridine cobalt dinitrogen compounds establish Co(I) centers in each case and a chelate-centered reduction in each of the sequential one-electron reduction steps. Frequency calculations successfully reproduce the experimentally determined N N infrared stretching frequencies and validate the computational methods. The electronic structures of the reduced cobalt dinitrogen complexes are evaluated in the broader context of bis(imino)pyridine base metal chemistry and the influence of the metal d electron configuration on the preference for closed-shell versus triplet diradical dianions.