Mono- and trimetallic cobalt (II) and monometallic cobalth (III) amine-bis(phenolate) complexes : synthesis and structural properties

• Main Author: Das, Uttam Kumar.
• Other Authors: Memorial University of Newfoundland. Dept. of Chemistry
• Format: Thesis
• Language: English
• Published: 2010
• Subjects: Cobalt compounds; Synthesis.; Cobalt-ammonium compounds; Ligands; Newfoundland studies; University of Newfoundland
• Online Access: http://collections.mun.ca/cdm/ref/collection/theses4/id/144806

Thesis (M.Sc.)--Memorial University of Newfoundland, 2010. Chemistry Includes bibliographical references This thesis describes the syntheses and structures of a series of monometallic and two trimetallic cobalt(II) amine-bis(phenolate) complexes. The protonated tripodal tetradentate ligand precursors dimethylaminoethylamino- N,N -bis(2-methylene-4,6-di-tert -butylphenol), H2[O2NN']BuBuNMe2 and diethylaminoethylamino- N,N -bis(2-methylene4,6-di-tert -amylphenol), H2[O2NN']AmAmNEt2 were reacted with cobaltous acetate tetrahydrate under varying conditions to afford both mono- and trimetallic species. X-ray crystallographic data of monometallic complexes [LCo[O2NN']BuBuNMe2] (L = H2O, CH3OH, CH3COCH3 , propylene oxide) showed that the Co II ion adopts a distorted trigonal bipyramidal coordination environment. In the absence of base and in the presence of excess cobaltous acetate, trimetallic complexes were isolated containing a central CoII in an octahedral environment coordinated to four CH3 OH and two bridging acetate ligands between two Co[O2 NN'] fragments with CoII in a trigonal bipyramidal setting. The mono- and trimetallic CoII complexes reported were also characterized by UV-vis spectroscopy, mass spectrometry, cyclic voltammetry and magnetic measurements. The CoII ions in these complexes are all high-spin and the trimetallic species show very weak antiferromagnetic behaviour when modeled as a linear isotropic trimer. Electrochemical studies reveal that the redox processes are most likely ligand based but a metal centered redox process is also possible. These works have recently been published: U. K. Das, J. Bobak, C. Fowler, S. E. Hann, C. F. Petten, L. N. Dawe, A. Decken, F. M. Kerton* and C. M. Kozak*, Dalton Trans. , 2010, 39, 5462. -- This thesis also describes several oxidation attempts and a successful synthesis of a monometallic CoIII amine-bis(phenolate) complex. The oxidation reactions were carried out using a variety of oxidizing agents under both aerobic and anaerobic conditions. However, only silver nitrate gave promising results in yielding a monometallic COIII amine-bis(phenolate) complex under aerobic conditions. The monometallic species was characterized by 1H NMR spectroscopy, mass spectrometry, and elemental analysis.