Department of Chemistry, University of California, Irvine, Irvine, California 92677-2025, United States.
Inorg Chem. 2021 Apr 5;60(7):5367-5375. doi: 10.1021/acs.inorgchem.1c00351. Epub 2021 Mar 18.
The nickel(II) complex [ON(H)O]Ni(PPh) ([ON(H)O] = bis(3,5-di--butyl-2-phenoxy)amine), bearing a protonated redox-active ligand, was examined for its ability to serve as a hydrogen atom (H) and hydride (H) donor. Deprotonation of [ON(H)O]Ni(PPh) afforded the square-planar anion {[ONO]Ni(PPh)}, whereas hydrogen atom transfer from [ON(H)O]Ni(PPh) to TEMPO in the presence of added PPh afforded five-coordinate [ONO]Ni(PPh) that has been structurally characterized. In solution, this five-coordinate complex exists in equilibrium with four-coordinate [ONO]Ni(PPh), 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(PPh) in the presence of PPh afforded the octahedral complex, [ONO]Ni(OTf)(PPh), which was characterized as an = 1, nickel(II) complex. Bond dissociation free energy (BDFE) and hydricity (Δ°) measurements benchmark the thermodynamic propensity of this complex to participate in ligand-centered H and H transfer reactions.
镍（II）配合物 [ON(H)O]Ni(PPh)（[ON(H)O] = 双（3,5-二-叔丁基-2-苯氧基）胺）作为氢原子（H）和氢化物（H）供体的能力研究
镍（II）配合物 [ON(H)O]Ni(PPh)（[ON(H)O] = 双（3,5-二-叔丁基-2-苯氧基）胺），带有质子化的氧化还原活性配体，研究了其作为氢原子（H）和氢化物（H）供体的能力。[ON(H)O]Ni(PPh) 的去质子化生成了正方形平面阴离子{[ONO]Ni(PPh)}，而在添加 PPh 的情况下，[ON(H)O]Ni(PPh) 向 TEMPO 的氢原子转移生成了五配位的[ONO]Ni(PPh)，该配合物已通过结构表征。在溶液中，这种五配位的配合物存在与四配位的[ONO]Ni(PPh)之间的平衡，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互变异构有关。在 PPh 的存在下，从 [ON(H)O]Ni(PPh) 中提取一个氢化物生成了八面体配合物 [ONO]Ni(OTf)(PPh)，该配合物被表征为一个 = 1 的镍（II）配合物。键离解自由能（BDFE）和氢化物（Δ°）测量基准了该配合物参与配体中心 H 和 H 转移反应的热力学倾向。
