24.
Hydroxide-bridged high-valent oxidants have been implicated as the active oxidants in methane monooxygenases and other oxidases that employ bimetallic clusters in their active site. To understand the properties of such species, bis-μ-hydroxo-Ni
II2 complex ( 1 ) supported by a new dicarboxamidate ligand (
N,
N′-bis(2,6-dimethyl-phenyl)-2,2-dimethylmalonamide) was prepared. Complex 1 contained a diamond core made up of two Ni
II ions and two bridging hydroxide ligands. Titration of the 1 e
− oxidant (NH
4)
2[Ce
IV(NO
3)
6] with 1 at −45 °C showed the formation of the high-valent species 2 and 3 , containing Ni
IINi
III and Ni
III2 diamond cores, respectively, maintaining the bis-μ-hydroxide core. Both complexes were characterised using electron paramagnetic resonance, X-ray absorption, and electronic absorption spectroscopies. Density functional theory computations supported the spectroscopic assignments. Oxidation reactivity studies showed that bis-μ-hydroxide-Ni
III2 3 was capable of oxidizing substrates at −45 °C at rates greater than that of the most reactive bis-μ-oxo-Ni
III complexes reported to date.
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