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The kinetics of oxidation of H 2 O 2 by [Ni III (cyclam)] 3+ , [Ni III L 1 ], was studied in aqueous acidic media at 25 • C and I = 0.5 M (NaClO 4). The [Ni III L 1 ] to [Ni II L 1 ] reduction was found to be fast in the presence of Cu(II) ion than the oxidation of the cyclam ligand by • OH. The rate constant showed an inverse acid dependence on H + ion at the pH range 1-1.5. The presence of sulphate retards the reaction. Macrocylic ligand oxidation was followed spectrophotometrically by examining the oxidation of nickel(II) complexes of macrocyclic ligands such as 1,8-bis(2-hydroxyethyl)-1,3,6,8,10,13-hexaazacyclotetradecane (L 2), ms-5,7,7,12,14,14hexamethyl-1,4,8,11-tetraazacyclotetradecane (L 3), rac-Me 6 [14]-4,11-dieneN 4 (L 4) by reaction with hydrogen peroxide. The rate constant for the cross reaction is discussed in terms of Marcus relationship.

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Iron (11) Reduction of trans-B is( d imet hylg lyoximato) halogenopyr id i neco balt (111) Complexes: Kinetics and Mechanism

With the aim of finding a suitable electrocatalyst for the efficient reduction of carbon dioxide, the electrochemistry of nickel (II) complex of 1,3,6,9,11,14-hexaazatricyclo [12⋅2⋅1⋅1] octadecane was studied using cyclic voltammetry (CV) and controlled-potential electrolysis (CPE) techniques in the presence and absence of CO 2 in 100% H 2 O, CH 3 CN-H 2 O mixtures (20-100%) and DMF-H 2 O (70-100%) mixtures. The efficiency of this process is determined using the coulometry technique. CO is the major product in the gaseous phase and HCOOH the sole product formed in the solution phase.

The kinetics of the oxidation of nickel (II) hexaaza and nickel (II) pentaaza macrocycles by the peroxydisulphate anion, S 2 O 8 2-, were studied in aqueous media. Effect of pH on reaction rate was also studied. The rate increases with increase of S 2 O 8 2concentration. Rates are almost independent of acid between pH 4 and 2, giving overall a relatively simple second-order rate law followed by oxidation within the ion pair solvent shell. Using rate = +1/2 d[Ni(L) 3+ ]/dt = k[Ni(L) 2+ ][S 2 O 8 2-], oxidation rate constants were determined.

Michael addition reactions of bis(amino acidato)metal(II) complexes (metal = copper, nickel, zinc; amino acid = glycine, dl-alanine, l-alanine) with acrylonitrile have been carried out under various experimental conditions in the absence of a base, resulting in mono- and disubstituted products in high yield, including partially hydrolyzed products. A reaction mechanism for the Michael addition on the nitrogen atom of the coordinated amino acid moiety, replacing the amino hydrogen atom(s), is proposed. All of the products have been characterized by Fourier transform infrared spectroscopy, electron paramagnetic resonance spectra, and elemental and electrochemical analyses. The single-crystal structures of bis( N-cyanoethylglycinato)copper(II) monohydrate ( 1a), diaquabis( N-cyanoethylglycinato)nickel(II), aquabis( N, N-dicyanoethylglycinato)copper(II) ( 2a), and bis[( N-propionamido- N-cyanoethyl)glycinato]copper(II) dihydrate ( 4a) have been confirmed by X-ray diffraction techniques. The products 1a, 2a, 4a, and bis( N-propionamidoglycinato)copper(II) monohydrate ( 3a) have been used as catalysts for the degradation of a phenol red dye and mild oxidation of various organic substrates in the presence of hydrogen peroxide. The monosubstituted complexes have been found to catalyze the reactions to a greater extent than the disubstituted complexes.

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