Metal ion chelates of lipophilic alkyl diazinyl ketoximes as hydrolytic catalysts

A series of lipophilic dodecyl hetaryl ketoximes (hetaryl = pyridin-2-yl, p yridazin-3-yl, pyrimidin-2-yl, pyrimidin-4-yl, pyrazin-2-yl as well as thei r methyl hetaryl homologues was synthesized and hydrolytic activity of thei r chelates with Co2+, Ni2+, Cu2+ and Zn2+ in a micellar matrix of hexadecyl trimethylammonium bromide or in homogeneous aqueous solutions was investiga ted using 4-nitrophenyl acetate, 4-nitrophenyl hexanoate and 4-nitrophenyl diphenyl phosphate as model substrates. While Co2+ and Cu2+ che,lates are a lmost inactive, those of Ni2+ and Zn2+ exhibit considerable activity. None of the studied chelates promotes hydrolysis of the used phosphate. The effe ctive species are chelates of the metal : ligand stoichiometry 1:3 and 1: 1 with Ni2+ and Zn2+, respectively, when the ester cleavage proceeds in the micellar matrix. The 1 :2 stoichiometry was found in aqueous solutions of N i2+ and Zn2+ chelates of methyl ketoximes.