Abstract
Abstract The square planar complex ion, Ni(C-rac-1,7-CTH)2+ (1,7-CTH = 5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacycloteradecane or tetb), theoretically can exist in 10 diasteredisomers, depending on the configurations of the four asysmmetric secondary amine center. The synthesis, characterization, x-ray structural and conformation studies of the five isomers were reported. Among these the molecular model of α-Ni(C-rac-1,7-CTH)2+ isomer indicates that the two axial sites are quite open and accessible to small monodentate ligands, as the methyl groups attached to the asymmetric carbons are all equatorial. According to Bosnich etal, the complex ionα-Ni(C-rac-1,7-CTH)2+, possesses trans-V configuration. With bidentate or even strong monodenate ligands, this isomeric form affords the cis-derivatives with the macrocyclic ligand is in folded state. Equilibrium constants and five coordinated ligand substitution kinetic studies on Cu(C-rac-1,7-CTH)2+ with monodentate ligands had been published. The study of substitution reaction in five coordinated complexes has given attention because they exist an intermediate state, in both a kinetic and steric sense, between the four coordinates complexes which are open to nucleophilic attack and the six coordinated systems which are not. In case of five coordinated complexes, both associative and dissociative mechanisms are possible by heiter added or lose of an monodentate ligands. In aprotic solvent the equilibrium constants for the reaction of Ni(TMC)2+ with halide ions reported. Here we report equilibrium constants for the reactions of α-Ni(C-rac-1,7-CTH)2+ with halide ion in aprotic solvents by kinetic and spectrophotometric methods and the x-ray crystal structure of five coordinated α-[Ni(C-rac-1,7-CTH)(Cl)](ClO4) complex.