Kinetics and mechanism of the oxidation of some carboxylates by a nickel (III) oxime-imine complex

✍ Scribed by Basudeb Saha; Amitava Dutta; Sumana Gangopadhyay; Pradyot Banerjee

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 115 KB
• Volume: 29
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/(sici)1097-4601(1997)29:3<225::aid-kin10>3.0.co;2-9

✦ Synopsis

The kinetics of the oxidation of formate, oxalate, and malonate by [Ni III (L 1 )] 2ϩ (where HL 1 ϭ 15-amino-3-methyl-4,7,10,13-tetraazapentadec-3-en-2-one oxime) were carried out over the regions pH 3.0 -5. 75, 2.80 -5.50, and 2.50 -7.58, respectively, at constant ionic strength and temperature 40ЊC. All the reactions are overall second-order with first-order on both the oxidant and reductant. A general rate law is given as

where k d is the auto-decomposition rate constant of the complex, k s is the electron transfer rate constant, n is the stoichiometric factor, and R is either formate, oxalate, or malonate. The reactivity of all the reacting species of the reductants in solution were evaluated choosing suitable pH regions. The reactivity orders are:

and k H 2 mal Ͼ k Hmal Ϫ Ͻ k mal 2Ϫ for the oxidation of formate, oxalate, and malonate, respectively, and these trends were explained considering the effect of hydrogen bonded adduct formation and thermodynamic potential.