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Enhanced Activity of [Ni(NHC)CpCl] Complexes in Arylamination Catalysis

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journal contribution
posted on 11.11.2013, 00:00 authored by Anthony R. Martin, Yusuke Makida, Sébastien Meiries, Alexandra M. Z. Slawin, Steven P. Nolan
Seven new air- and moisture-stable nickel complexes bearing flexible bulky NHC (N-heterocyclic carbene) ancillary ligands (NHC = IPr*, IPr*Tol, IPr*OMe, IPent) are reported. Using experimentally determined crystal structures, the steric environments of [Ni­(NHC)­CpCl] complexes were analyzed. A survey of their catalytic activity in Buchwald–Hartwig arylamination has been performed. In comparison to less sterically demanding analogues (NHC = IMes, SIMes, IPr, SIPr), an increase in the ligand bulkiness was found to correlate to a dramatic enhancement of the C–N bond formation efficiency. Finally, the catalytic activity of the most active precatalyst, [Ni­(IPr*OMe)­CpCl], was further explored and the scope and limitations of this complex were examined.

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