Synthetic and kinetic studies of polyamine and macrocyclic complexes

Abstract

The thesis consists of four sections. Section I deals with complexes of the general type [Co (tetren) X]n+ (where tetren is 1, 11-diamino-3,6,9-triaza-undecane=tetraethylenepentamine and X is a unidentate ligand). Several geometric isomers are possible and synthetic methods have been developed to prepare pure isomers rather than isomeric mixtures. The complexes have been characterised by i.r., 13C n.m.r. and d-d spectra. The kinetics of base hydrolysis of the various isomers of [Co(tetren)X)n+ have been studied (X = Cl-, Br-, NO2-, DMF, DMSO, O2CH, O2CCH3, O2CC2H5, -O2CCH2C1, -O2CCHC12, NCCH3, NCC6H5 and NCC6H4OMe). Activation parameters for base hydrolysis (X = C1- and Br-) have been determined and Hg(II) promoted aquation studied. The acid catalysed decarboxylation of [Co (tetren) OCO2]+ has been studied and activation parameters obtained. The reaction of N3- with [Co(tetren)NCCH3]3+ gives the tetrazolato complex (Co(tetren)-N4CCH3)2+ and this reaction has been studied kinetically. The tetraxolato complexes [Co(tetren) N4CR]2+ (R = Me, Ph) have been isolated and chalracterised. Section II discusses complexes of the type [Co(trien)- (A)C1)2+ (trien = 1,8-diamino-3.7-diazaoctane and A is α mono-dentate amine, imidazole (ImH), pyridine (py), n-butylamine (BunNH2) and 2,2-dimethoxyethylamine (NH2CH2CH(OCH3) 2). Reactions of (Co(trien)Cl2]+ with ImH, BUNH2 and (NH2CH2CH(OCH3)2) gave cis-α-[Co(trien) (A)C1] while for A=py the complex cis-β2-[Co(trien) (py)C1]2+ was isolated. Base hydrolysis kinetics were measured for the four complexes and the kinetics of the mercury (11) promoted aquation of cis-β2-[Co (trien) - (py)C1]2+ studied.

Section III concerns the preparation of the open chain diamide ligands shown in structures (1) LAH2, (2) LBH2, and (3) LCH2. Copper (11) and nickel (11) gave cationic complexes, [M(LH2)] (C1O4)2 structure (4) and under basic conditions neutral complexes of the deprotonated ligands [M(L-2H)] structure (5). Redox studies were carried out on the neutral complexes with the ease and reversibility of the oxidation processes examined as a function of ligand structure.

Section IV describes the preparation of diamide macrocyclic ligands prepared by the condensation of diethyl malonate with (a) 1,4 .7 ,10-tetra-azacyclotridecane-11,13-dione, (b) 1,4,8,11-tetra-azacyclotetradecane-11,13-dione, (c) 1,4,8,12-tetra-azacyclodent adecane-12, 14-dione and (d) tetraethylene-pentamine. Complexation of the resultant ligands with Cu(11). Ni(11) and Pd(11) were examined using pH and spectrophotometric titrations. Redox studies were performed on complexes of the deprotonated amides [ML] for M = Cu(11) and Ni(11) and the reversibility of the oxidations examined as a function of the metal ion and the ligand structures.