Ni(I) and Ni(II) ring-expanded N-heterocyclic carbene complexes: C–H activation, indole elimination and catalytic hydrodehalogenation

Reaction of the bulky 6-membered N-heterocyclic carbene 6-Mes with Ni(cod)2 gives a C–H activated 6-Mes nickel(II) complex, but the novel three-coordinate Ni(I) species Ni(6-Mes)(PPh3)Br if the reaction is performed in the presence of Ni(PPh3)2Br2. The Ni(I) complex is a precursor for the catalytic hydrodehalogenation of aryl halides.