Exploring Ligand-Centered Hydride and H-Atom Transfer
Exploring Ligand-Centered Hydride and H-Atom Transfer
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DOI：
10.1021/acs.inorgchem.1c00351
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发表时间：
2021-03-18
影响因子：
4.6
通讯作者：
Heyduk, Alan F.
中科院分区：
文献类型：
--
作者：
Charette, Bronte J.;Ziller, Joseph W.;Heyduk, Alan F.
研究了镍（II）配合物[ON（H）O]Ni（PPh 3）（[ON（H）O]（2-）=双（3，5-二叔丁基-2-苯氧基）胺）作为氢原子（H-中心点）和氢化物（H-）供体的能力。[ON（H）O]Ni（PPh 3）的去质子化得到平面正方形阴离子{[ONOcat]Ni（PPh 3）}（1-），而在PPh 3存在下氢原子从[ON（H）O]Ni（PPh 3）转移到克里思中心点得到五配位的[ONO]Ni（PPh 3）（2），其结构已被表征。在溶液中，这种五配位络合物与四配位[ONO]Ni（PPh 3）平衡存在，并且这种配体交换平衡与氧化还原活性配体和镍中心之间的价态互变异构相关。在PPh 3存在下，从[ON（H）O]Ni（PPh 3）中提取氢化物，得到八面体配合物[ONOq]Ni（OTf）（PPh 3）（2），其特征在于S = 1，镍（II）配合物。键解离自由能（BDFE）和水合度（Δ G（H-）度）测量基准的热力学倾向，这种复杂的参与配体为中心的H-中心点和H-转移反应。
The nickel(II) complex [ON(H)O]Ni(PPh3) ([ON(H)O](2-) = bis(3,5-di-tert-butyl-2-phenoxy)amine), bearing a protonated redox-active ligand, was examined for its ability to serve as a hydrogen atom (H-center dot) and hydride (H-) donor. Deprotonation of [ON(H)O]Ni(PPh3) afforded the square-planar anion {[ONOcat]Ni(PPh3)}(1-), whereas hydrogen atom transfer from [ON(H)O]Ni(PPh3) to TEMPO center dot in the presence of added PPh3 afforded five-coordinate [ONO]Ni(PPh3)(2) that has been structurally characterized. In solution, this five-coordinate complex exists in equilibrium with four-coordinate [ONO]Ni(PPh3), and this ligand exchange equilibrium correlates with a valence tautomerization between the redox-active ligand and the nickel center. Abstraction of a hydride from [ON(H)O]Ni(PPh3) in the presence of PPh3 afforded the octahedral complex, [ONOq]Ni(OTf)(PPh3)(2), which was characterized as an S = 1, nickel(II) complex. Bond dissociation free energy (BDFE) and hydricity (Delta G(H-)degrees) measurements benchmark the thermodynamic propensity of this complex to participate in ligand-centered H-center dot and H- transfer reactions.