Synthesis and structural characterization of aryloxo-functionalized N-heterocyclic carbene complexes of nickel(II)

The reaction of Ni(PPh3)2Br2 with two equivalents of anionic aryloxo-functionalized N-heterocyclic carbene [NaO-4,6-di-tBu-C6H2-2-CH2{C(NCHCHNR)}] (R = iPr, NaL1; R = Bz, NaL2), which are generated in situ by the reaction of the corresponding salt H2LCl with two equivalents of NaN(SiMe3)2, affords bis-ligand complexes of View the MathML sourceL21Ni (3) and View the MathML sourceL22Ni (4) in good yield, respectively. It is interesting to note that still the bis-ligand one not the mono-ligand Ni(II) halide is obtained, even the molar ratio of NaL1or NaL2 to Ni(PPh3)2Br2 is changed to 1:1. Complexes of 3 and 4 have been fully characterized including the X-ray structure determination. The structural analysis shows that each nickel atom in 3 or 4 is bonded to two bidentate ligands L1 or L2, respectively, in a cis arrangement.