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Nucleophilic versus Electrophilic Reactivity of Bioinspired Superoxido Nickel(II) Complexes

2018; Wiley; Volume: 57; Issue: 45 Linguagem: Inglês

10.1002/anie.201808085

1521-3773

Chakadola Panda, Anirban Chandra, Teresa Corona, Erik Andris, Bhawana Pandey, Somenath Garai, Nils Lindenmaier, Silvio Künstner, Erik R. Farquhar, Jana Roithová, Gopalan Rajaraman, Matthias Drieß, Kallol Ray,

Metalloenzymes and iron-sulfur proteins

Abstract The formation and detailed spectroscopic characterization of the first biuret‐containing monoanionic superoxido‐Ni II intermediate [LNiO 2 ] − as the Li salt [ 2 ; L=MeN[C(=O)NAr) 2 ; Ar=2,6‐iPr 2 C 6 H 3 )] is reported. It results from oxidation of the corresponding [Li(thf) 3 ] 2 [LNi II Br 2 ] complex M with excess H 2 O 2 in the presence of Et 3 N. The [LNiO 2 ] − core of 2 shows an unprecedented nucleophilic reactivity in the oxidative deformylation of aldehydes, in stark contrast to the electrophilic character of the previously reported neutral Nacnac‐containing superoxido‐Ni II complex 1 , [L′NiO 2 ] (L′=CH(CMeNAr) 2 ). According to density‐functional theory (DFT) calculations, the remarkably different behaviour of 1 versus 2 can be attributed to their different charges and a two‐state reactivity, in which a doublet ground state and a nearby spin‐polarized doublet excited‐state both contribute in 1 but not in 2 . The unexpected nucleophilicity of the superoxido‐Ni II core of 2 suggests that such a reactivity may also play a role in catalytic cycles of Ni‐containing oxygenases and oxidases.