The bisadduct (cAAC)₂Ni^IICl₂ [1; cAAC = cyclic (alkyl)(amino)carbene] was directly synthesized by treating cAAC with NiCl₂. Compound 1 was reduced to (cAAC)₂Ni⁰ (2) by using lithium diisopropylamide or KC₈. Crystals of 2 were stable under an inert gas for several months and decomposed upon heating above 165 °C. On the basis of the calculated natural bond orbital charge values of the nickel atom in 2, the oxidation state of nickel was determined to be between Ni^I and Ni⁰ (+0.34). Theoretical calculations suggested a closed-shell singlet electronic configuration of 2 with little biradical character. Ab initio multiconfigurational C(R)ASSCF/CASPT2 calculations predicted a closed-shell singlet electronic configuration (Ni⁰), whereas excited spin states possessed Ni^I character with unpaired electrons on neighboring carbon atoms. The catalytic activity of complex 2 was investigated for the homocoupling of various unactivated aryl chlorides/fluorides. The biaryls were obtained in good yields at moderate temperature. Theoretical studies showed that an intermediate containing Ni^III was more favored than one with Ni^IV.