Nickel complexes imine oximes

Concentrated nitric acid has been used to obtain nickel(III) complexes like [Ni L(N03)2]CI04 starting from [NPL](C104)2 (L = cyclam, Megcyclam) in aqueous solutions. Oxidation of the parent nickel(II) with nitric acid complexes also afforded the nickel(IV) species [Ni L] ( 104)2 where L is the amine-imine-oxime ligand (415) or... 

The mixed amine-imine-oxime ligands HL (415) and HT (416) have been found to be effective in stabilizing nickel(IV). The complexes Ni(L)(C104)2 (418) and Ni(T)2(C104)2 (419) can be obtained by oxidation of solutions of the parent nickel(II) complexes with various oxidizing agents (I Os, SiOl", Pb02, Fe(bipy) ) or electrochemically. ... 

Comparisons can be drawn between the chemistry of [Ni,v(dmg)3]2-and that of the sexidentate bis oxime imine complex [Ni,vMezL]2+, which is much better characterized from a thermodynamic point of view (45, 56). It can be optically resolved (54) and shows no indications of protonation above pH 0. The isostructural nickel(III) and nickel(II) complexes are subject to protonation and are much more labile to substitution. Protonation of the oxime-imine chromophore destabilizes the higher oxidation states. 

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