Isolation of a Bimetallic Cobalt(III) Nitride and Examination of Its Hydrogen Atom Abstraction Chemistry and Reactivity toward H 2
Isolation of a Bimetallic Cobalt(III) Nitride and Examination of Its Hydrogen Atom Abstraction Chemistry and Reactivity toward H 2
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双金属氮化钴 (III) 的分离及其氢原子抽象化学和 H 2 反应性的检测
DOI：
10.1021/jacs.0c00291
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发表时间：
2020
影响因子：
15
通讯作者：
Fortier, Skye
中科院分区：
文献类型：
--
作者：
Sengupta, Debabrata;Sandoval-Pauker, Christian;Schueller, Emily;Encerrado-Manriquez, Angela M.;Metta-Magaña, Alejandro;Lee, Wen-Yee;Seshadri, Ram;Pinter, Balazs;Fortier, Skye
在室温下，双（叠氮）钴（II）配合物[Na（THF）x][（ketguan）Co（N3）2]（ketguan = [（tBu 2CN）C（NDipp）2]−，Dipp = 2，6-二异丙基苯基）（3a）在THF中的光解干净地形成双核氮化钴Na（THF）4{[（ketguan）Co（N3）]2（μ-N）}（1）。化合物1代表了第一个可分离的，可分离的氮化钴络合物的例子，它已经通过光谱，磁性和计算分析得到了充分的表征。密度泛函理论支持的CoIII <$N <$CoIII典型的形式与显着的π键之间的钴中心和氮化物原子。与其他9族桥接氮化物配合物不同，在1的桥接N原子处没有检测到自由基特征。事实上，1对弱C-H供体不起反应，甚至在其晶体学晶胞中与环己二烯（CHD）分子共结晶，得到室温稳定的产物1·CHD。值得注意的是，向[（ketguan）Co（N3）（py）]2（4a）的1或光解溶液中加入吡啶，通过活化氮化物单元导致不稳定，导致由强C-H键（BDE ≤ 100 kcal/mol）的分子间氢原子夺取（HAA）形成的混合价Co（II）/Co（III）桥接亚氨基物种[（ketguan）Co（py）][（ketguan）Co]（μ-NH）（μ-N3）（5）。在C6 H 12或C6 D 12存在下，5形成的动力学速率分析给出KIE = 2.5 ± 0.1，支持HAA形成途径。通过在氢气和氘气氛（150 psi）下光解4 a的苯/吡啶溶液进一步研究了该体系的反应性，由于氢气的活化，该体系分别生成了双亚氨基配合物[（ketguan）Co（μ-NH）]2（6）和[（ketguan）Co（μ-ND）]2（6-D）.这些结果为后期3d金属氮化物的化学和电子结构提供了独特的见解，同时为C-H活化途径提供了入口。
Room temperature photolysis of the bis(azide)cobaltate(II) complex [Na(THF)x][(ketguan)Co(N3)2] (ketguan = [(tBu2CN)C(NDipp)2]−, Dipp = 2,6-diisopropylphenyl) (3a) in THF cleanly forms the binuclear cobalt nitride Na(THF)4{[(ketguan)Co(N3)]2(μ-N)} (1). Compound1represents the first example of an isolable, bimetallic cobalt nitride complex, and it has been fully characterized by spectroscopic, magnetic, and computational analyses. Density functional theory supports a CoIII═N═CoIIIcanonical form with significant π-bonding between the cobalt centers and the nitride atom. Unlike other group 9 bridging nitride complexes, no radical character is detected at the bridging N atom of1. Indeed,1is unreactive toward weak C–H donors and even cocrystallizes with a molecule of cyclohexadiene (CHD) in its crystallographic unit cell to give1·CHD as a room temperature stable product. Notably, addition of pyridine to1or photolyzed solutions of [(ketguan)Co(N3)(py)]2(4a) leads to destabilization via activation of the nitride unit, resulting in the mixed-valent Co(II)/Co(III) bridged imido species [(ketguan)Co(py)][(ketguan)Co](μ-NH)(μ-N3) (5) formed from intermolecular hydrogen atom abstraction (HAA) of strong C–H bonds (BDE ∼ 100 kcal/mol). Kinetic rate analysis of the formation of5in the presence of C6H12or C6D12gives a KIE = 2.5 ± 0.1, supportive of a HAA formation pathway. The reactivity of our system was further probed by photolyzing benzene/pyridine solutions of4aunder H2and D2atmospheres (150 psi), which leads to the exclusive formation of the bis(imido) complexes [(ketguan)Co(μ-NH)]2(6) and [(ketguan)Co(μ-ND)]2(6-D), respectively, as a result of dihydrogen activation. These results provide unique insights into the chemistry and electronic structure of late 3d metal nitrides while providing entryway into C–H activation pathways.