ELECTRONIC TUNING OF ARYLNICKEL(II) COMPLEXES BY PARA SUBSTITUTION OF THE TERDENTATE MONOANIONIC 2,6-BIS[(DIMETHYLAMINO)METHYL]PHENYL LIGAND

Aryl bromides of the type BrC6H2(CH2NMe2)2-2,6-R-4 (R = NH2, MeO, H, Cl, MeC(O)) have been synthesized and have been used to prepare the corresponding organonickel(II) complexes [Ni{C6H2(CH2NMe2)2-2,6-R-4}Br] by an oxidative addition reaction to Ni0(COD)2 (COD = cycloocta-1,5-diene). The effect that the para substituent of the monoanionic, N,C,N' terdentate, aryl ligand has on the electronic properties of the nickel complexes has been investigated by C-13 NMR and UV/vis spectroscopy as well as by electrochemistry. The results show that para substitution on the aryl ligand markedly influences the nickel(II) center; electron-donating substituents increase the ease of oxidation to Ni(III), and direct correlations exist between chemical shift data for the carbon atom bonded to nickel and appropriate Hammett parameters.