SCHEDULED MAINTENANCE
Half-sandwich nickel complexes with ring-expanded NHC ligands – synthesis, structure and catalytic activity in Kumada–Tamao–Corriu coupling†
P. A.
Guńka 
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Abstract
The general synthesis of [Ni(Cp)(X)(NHC)] complexes from a nickel halide, CpLi, and a carbene solution is reported. This procedure yields unprecedented complexes with ring-expanded NHC ligands (RE-NHC) of six- (1a, 1b), seven- (1c), and eight-membered (1d) heterocycles. The NMR spectra of 1a–1d are consistent with the hindered rotation of Ni–Ccarbene and N–CMes bonds, while X-ray analyses of 1b, 1c, and 1d reveal a pronounced trans influence of the RE-NHC ligands. Complexes 1a–1e are efficient pre-catalysts in Kumada–Tamao–Corriu coupling with the maximum efficiency observed for complexes bearing the six-membered NHC.
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