Enzyme-assisted matrix isolation of novel dithiooxamide complexes of nickel(II)

Abstract

The complexation reaction proceeding on the Ni(II) hexacyanoferrate(II) matrix immobilized in the gelatin layer in contact with an alkaline solution of dithiooxamide has been studied. It has been shown that five different complexes can be obtained. four of which, i.e. (Ni₂L)₂[Fe(CN)₆] (I), NiL(H₂O)₂ (II), [NiL(H₂O)₂]_n(III) and [Ni(HL)₂]_n(IV) are in soluble and one of them, [NiL₂]^2- (V) is soluble in water (HL^- is a partially deprotonated ligand form, L^2- is fully deprotonated form). When ligand concentration in the solution is smaller than 1.0 x 10^{- 3} mol.dm^-3. surface Ni₂[Fe(CN)₆] concentration in the matrix more than 2.0 x 10^-2mol.m^-2 and a (0.5-1.0) min time of compIexing process, chelateI (λ_max = 590-610 nm) is formed; when ligand concentration ≃2.0 x 10^-3 - 2 0 x 10^-2mol dm^-3 and Nb[Fe(CN)₆] concentration is smaller than 4.0 x 10^-2 mol.m^-2, chelate II (λ_max=580 nm) is formed; when ligand concentration ≃2.0 x 10^-2- 5.0.10 ^-2 mol.dm^-3 and Ni₂ [Fe(CN)₆] concentration is more than 2.0 x 10^-2 mol.m ^-2, chelate III (λ_max = 570 nm) is realized. It has been pointed out that chelate II is capable of an irreversible transformation into chelate IV upon processing in acid solution. When ligand concentration is more than 10^-3 mol.dm^-3 and Ni₂[Fe(CN)₆ concentration is smaller than 2.0 x 10^-2, complex V is formed. The structures of compounds I-V have been proposed and it has been indicated that chelate III and IV are coordination polymers. It has also been pointed out that complexation reaction on the immobilized Ni₂[Fe(CN)₆] matrix in the Ni(II)-dithiooxamide system enables one to obtain more complex forms than with complexing in the same system in aqueous solution.