A thermodynamic study of transition metal oxime complexes
Degree GrantorUniversity of Canterbury
Degree NameDoctor of Philosophy
This thesis reports the preparation of the O-methyldioxime and bis(O-methyloxime) derivatives of the diamine 4,4,9,9-tetramethyl-5,8-diazadodecane-2,11-dione ,and the preparation of the oxime and O-methyloxime derivatives of the diamine 2,6,6-trimethyl-2,5-diazanonan-8-one. The chelating reactions of the diamine dioximes (tetradentate ligands) and the diamine oximes (tridentate ligands) towards divalent transition metal ions have been studied. The E,Z configurations of these ligands were determined by p.m.r. spectroscopy. The rates of acid catalysed E-Z isomerization of the oxime and O-methyloxime groups, as determined by p.m.r. spectroscopy, are reported. The observed rates of isomerization are oxime > O-methyloxime. Thermodynamic data are reported for the stepwise amino protonation of the tetradentate diamine dioxime ligands (log K (potentiometric), ΔH (calorimetric) and ΔS) and of the tridentate diamine oxime ligands (log K) at 25.0°C and I = 0.10M NaCl. Log K (potentiometric) data are reported for (1) the formation of complexes between the diamine dioxime ligand and the divalent metal ions Fe, Ni and Zn and are compared with the known values for Co and Cu, (2) the formation of complexes between the diamine O-methyldioxime and the divalent metal ions Co, Ni, Cu and Zn, and (3) the formation of the copper(II) complex of the diamine bis(O-methyldioxime) at 25.0°C and I = 0.10H NaCl. ΔH (calorimetric) at ΔS data are also reported for the formation of copper(II) complexes of the tetradentate ligands and these are interpreted in terms of the known structural date. Log K data are reported for the formation of the copper(II) complexes of the tridentate diamine oxime ligands. The order of donor strengths observed is oximato >> oxime> O-methyloxime. Deprotonation from a complexed oxime group involves the formation of either an intramolecular hydrogen bond or hydrogen bonds with the solvent. Intramolecular oxime-oximato hydrogen bonding is favoured by a positive entropy change.