A Catalyst with Two-Coordinate Nickel: Theoretical and Catalytic Studies
Mondal, Kartik Chandra × Samuel, Prinson P Li, Yan Roesky, Herbert W Roy, Sudipta Ackermann, Lutz Sidhu, Navdeep S Sheldrick, George M Carl, Elena Demeshko, Serhiy De, Susmita Parameswaran, Pattiyil Ungur, Liviu Chibotaru, Liviu Andrada, Diego M #
WILEY-V C H VERLAG GMBH
EUROPEAN JOURNAL OF INORGANIC CHEMISTRY vol:2014 issue:5 pages:818-823
The bisadduct (cAAC)2NiIICl2 [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 NiI 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 NiI 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 NiIII was more favored than one with NiIV.