Institute of Chemistry: Metalorganics and Inorganic Materials, Technische Universität Berlin, Strasse des 17. Juni 135, Sekr. C2, 10623 Berlin, Germany.
Chemistry. 2010 Aug 16;16(31):9669-75. doi: 10.1002/chem.201001138.
Although O(2) activation by metals such as iron and copper has been a matter of intensive research in the last decades, this type of chemistry for nickel systems is still in its infancy. Moreover, studies regarding the oxidizing ability of the resulting "Ni(n)-O(2)" species towards exogenous substrates are scarce. In this work, we report on the reactivity of an isolable and thermally stable mononuclear superoxo-nickel compound [Ni(II)(beta-diketiminato)(O(2))] (1) towards different types of organic substrates. In addition, we have been able to prove that the beta-diketiminato ligand can undergo partial intramolecular oxidation due to close proximity between the isopropyl groups of the beta-diketiminato-aryl and the superoxo subunits. Compound 1 performs hydrogen-atom abstraction from O-H and N-H groups and most importantly it shows an unprecedented dioxygenase-like reactivity in the oxidation of 2,4,6-tri-tert-butylphenol. The latter reaction most likely occurs through the mediation of a putative [Ni(III)-oxo] intermediate, affording an unprecedented oxidation product of the phenol that incorporates two oxygen atoms from a single O(2) subunit. Results presented herein provide evidence of the striking oxidizing ability of dioxygen-nickel species and further support the viability to use such systems as oxidation catalysts analogous to its heavy metal congener, palladium.
尽管铁和铜等金属的 O(2) 活化作用在过去几十年中一直是研究的热点，但镍体系的这种化学性质仍处于起步阶段。此外，关于生成的“Ni(n)-O(2)”物种对外源底物的氧化能力的研究还很少。在这项工作中，我们报告了一种可分离和热稳定的单核过氧镍化合物Ni(II)(β-二酮亚胺基)(O(2))对不同类型有机底物的反应性。此外，我们已经能够证明β-二酮亚胺配体由于β-二酮亚胺基-芳基的异丙基基团与过氧亚基之间的接近，可以发生部分分子内氧化。化合物 1可以从 O-H 和 N-H 基团中抽取氢原子，最重要的是，它在氧化 2,4,6-三-叔丁基苯酚时表现出前所未有的双氧酶样反应性。后一种反应很可能是通过假定的[Ni(III)-氧]中间体介导的，从而得到了一个前所未有的苯酚氧化产物，其中包含一个 O(2)亚基的两个氧原子。本文提供的结果证明了双氧酶镍物种的惊人氧化能力，并进一步支持了使用此类系统作为氧化催化剂的可行性，类似于其重金属同系物钯。
