Comprehensive comparison between the reaction of N,N'-cyclohexane-1,2-diylidene-bis(4-methoxybenzoylhydrazide) with mercury(II) and copper(II) ions. Synthesis, structure, and kinetics of complex formation

Abstract

Comprehensive comparison between the reaction of N,N'-cyclohexane-1,2-diylidene-bis(4-methoxybenzoylhydrazide) (CHMBH) with HgCl2 and Cu(NO3)2 · 2.5H2O salts have been investigated, including the synthesis, structure and kinetic of complex formation. The reactions of CHMBH with HgCl2 or Cu(NO3)2 · 2.5H2O at the same synthetic conditions have been shown to produce completely different type of complexes: [Hg(CHMBH)Cl2] · CH3CN (I) and [Cu3(μ3-OH)(CTMB)3(NO3)2(CH3CN)2] · 5CH3CN · H2O (II) (CTMB = cyclohexotriazole-3-(4-methoxybenzamide)). The prepared compounds were characterized using different techniques (NMR, IR, UV-Vis and mass spectroscopies, microelemental analysis, thermogravimetry as well as X-ray powder differection and X-ray single crystal crystallography for I (CIF file CCDC no. 1503398). X-ray crystallography shows that the isolated product of I is a mononuclear complex which contains the [Hg(CHMBH)]2+ core. While, the isolated product of II was a trinuclear Cu(II) cluster [Cu3(μ3-OH)(CTMB)3(NO3)2(CH3CN)2] · 5CH3CN · H2O which contains three differently coordinated copper sites. Kinetic studies on the formation of I have been also investigated and compared with that of II. In case of I, the reaction was so slow and exhibits a first-order dependence on the concentration of metal salt and a first-order dependence on the concentration of CHMBH. While in II, the study shows that the reaction is fast and occurs in three distinct phases.