Panda, C.; Chandra, A.; Coron, T.; Andris, E.; Pandey, B.; Garai, S.; Lindenmaier, N.; Künstner, S.; Farquhar, E.R.; Roithová, J.; Rajaraman, G.; Driess, M.; Ray, K.: Nucleophilic versus Electrophilic Reactivity of Bioinspired Superoxido Nickel(II) Complexes. Angewandte Chemie - International Edition 57 (2018), p. 14883-14887
10.1002/anie.201808085
Open Access Version (externer Anbieter)
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 sucha reactivity may also play a role in catalytic cycles of Ni-containing oxygenases and oxidases.