Samantaray, Manoja K. Shaikh, Mobin M. Ghosh, Prasenjit Rare [(NHC)<sub>2</sub>Ni-OH]-Type Terminal Nickel Hydroxo and [(NHC)<sub>2</sub>Ni]-Type Complexes of <i>N</i>/<i>O</i>-Functionalized N-Heterocyclic Carbenes as Precatalysts for Highly Desirable Base-Free Michael Reactions in Air at Ambient Temperature Highly convenient base-free Michael reaction of β-dicarbonyl, β-keto ester, and α-cyano ester compounds with activated ethylene compounds in air at ambient temperature catalyzed by a series of new nickel complexes, <b>1b</b>−<b>4b</b>, of <i>N</i>/<i>O</i>-functionalized N-heterocyclic carbenes (NHC) are reported. Quite interestingly, of these nickel complexes, <b>1b</b> and <b>2b</b> were found to be of the [(NHC)<sub>2</sub>Ni-OH] type bearing a terminal [Ni-OH] moiety and are among the few known structurally characterized examples of monomeric terminal [Ni-OH] complexes. Compounds <b>3b</b> and <b>4b</b>, on the other hand, were found to be of the commonly encountered [(NHC)<sub>2</sub>Ni]-type complexes. More significantly, both the [(NHC)<sub>2</sub>Ni-OH]-type complexes <b>1b</b> and <b>2b</b> and the [(NHC)<sub>2</sub>Ni]-type complexes <b>3b</b> and <b>4b</b> were synthesized using same synthetic methodology by sheer modulation of the N-substituents on the N-heterocyclic carbene ring by the reaction of the imidazolium chloride salts with NiCl<sub>2</sub>·6H<sub>2</sub>O in the presence of K<sub>2</sub>CO<sub>3</sub> as a base. nickel complexes;2 b;4 b;2CO;Compounds 3 b;NHC;imidazolium chloride salts 2009-04-13
    https://acs.figshare.com/articles/dataset/Rare_NHC_sub_2_sub_Ni_OH_Type_Terminal_Nickel_Hydroxo_and_NHC_sub_2_sub_Ni_Type_Complexes_of_i_N_i_i_O_i_Functionalized_N_Heterocyclic_Carbenes_as_Precatalysts_for_Highly_Desirable_Base_Free_Michael_Reactions_in_Air_at_Ambient_Temperature/2864887
10.1021/om801186f.s003