Stoichiometric and Catalytic Aryl-Cl Activation and Borylation using NHC-stabilized Nickel(0) Complexes.

NHC-nickel (NHC=N-heterocyclic carbene) complexes are efficient catalysts for the C-Cl bond borylation of aryl chlorides using NaOAc as a base and B2 pin2 (pin=pinacolato) as the boron source. The catalysts [Ni2 (ICy)4 (μ-(η2 :η2 )-COD)] (1, ICy=1,3-dicyclohexylimidazolin-2-ylidene; COD=1,5-cyclooctadiene), [Ni(ICy)2 (η2 -C2 H4 )] (2), and [Ni(ICy)2 (η2 -COE)] (3, COE=cyclooctene) compare well with other nickel catalysts reported previously for aryl-chloride borylation with the advantage that no further ligands had to be added to the reaction. Borylation also proceeded with B2 neop2 (neop=neopentylglycolato) as the boron source. Stoichiometric oxidative addition of different aryl chlorides to complex 1 was highly selective affording trans-[Ni(ICy)2 (Cl)(Ar)] (Ar=4-(F3 C)C6 H4 , 11; 4-(MeO)C6 H4 , 12; C6 H5 , 13; 3,5-F2 C6 H3 , 14).