Kinetics and Mechanism of the Ligand Exchange Reaction Between Tetraaza Macrocycle Ligand and Cu(II) Tetradentate Amine-Amide Complexes

Abstract

The kinetics of the ligand exchange reaction of tetraaza macrocycle, teazma (teazma is 5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene dihydrogen perchlorate) with Cu(bcen) 2+ and Cu(bctn) 2+ , where bcen and bctn are N,N'-bis(β-carbamoylethyl) ethylendiamine) and N,N'-bis(β-carbamoylethyl) propylendiamine), respectively, have been studied by visible spectrophotometry in dimethylformamide, DMF, solvent at 25 ± 0.2 °C. In the system of Cu(bctn) 2+ /teazma, the ligand exchange reaction proceeds in a two-step-consecutive manner, with two rate constants k bctn obsd (1) and k bctn obsd (2). The first reaction step was dependent on the concentration of teazma macrocycle, while the second reaction step was independent. However, it is found that the ligand exchange reaction in Cu(bcen) 2+ /teazma proceeds in an one-step with the rate constant k bcen obsd. The rate constant is dependent on [teazma] macrocycle. The ligand exchange reaction in the system of Cu(bcen) 2+ /teazma is not complete and after some progress, the reaction reaches equilibrium. On the basis of results, a reaction mechanism is proposed and discussed for the ligand exchange rate.

Synthesis of Hetero- and Homo-multinuclear Complexes with a Tetracyanonickelate Anion: Structural Characterization [Cu(bcen)Ni(CN)4]2

“…There have been a few studies on the formation and dissociation of the Cu(bcen) 2+ complex and also on the kinetics of metal exchange complexes with the bcen ligand, and they reported that the Cu(II)-O bond to the amide is substitutionally labile. 25,26,33 The X-ray characterization of complex 1 shows that the bond between Cu(II) and a labile amide oxygen of bcen ligand has broken under these experimental conditions, followed by coordination of Cu(II) to cyanide nitrogen atoms of Ni(CN) 4 2-moieties. The distance between copper ion (Cu1) and the amide oxygen of the dangling arm of an adjacent tetranuclear species (O2a, symmetry code: -x + 1, -y + 1, -z + 1) is 2.9070(15) Å which is significantly longer than the typical Cu-O covalent bond (1.98 Å), but it is slightly shorter than the sum of the van der Waals radii (2.92 Å).…”

“…23 The diamine-diamide ligand 4,7-diazadecanediamide (bcen) was prepared as previously reported from ethylendiamine and acrylamide in acetonitrile by heating the mixture under reflux. [24][25][26] The white powder was re-crystallized from CHCl 3 . Infrared spectra were taken with an Equinox 55 Bruker FT-IR spectrometer using KBr pellets in the 400-4000 cm -1 range.…”

A 26-Membered Macrocycle Obtained by a Double Diels–Alder Cycloaddition Between Two 2H-Pyran-2-one Rings and Two 1,1'-(Hexane-1,6-diyl)bis (1H-pyrrole-2,5-dione)s

“…[10][11][12][13][14] Of interest are also preparations of calix [4]arene systems linked with 1,2,4-triazole and 1,3,4-oxadiazole derivatives, 15 as well as other tetraaza macrocycles applied as ligands in various coordination compounds. 16 Herein we present another approach, where two double Diels-Alder cycloadditions between two molecules of the substituted 2H-pyran-2-ones (each acting as a "double" diene) 17 and two molecules of the double dienophile provide a 26-membered tetraaza macrocyclic system. This strategy can be termed a multicomponent reaction (as four molecules react to form the macrocycle) with four individual [4+2] pericyclic reactions representing the crucial ring-closing steps.…”