Thesis (Ph. D.)--University of Wisconsin--Madison, 1968. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Bibliography: leaves [289]-313.

Thesis (M.S.)--University of Wisconsin, 1970. / Typescript (photocopy). eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (p. [97]-101).

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The study involves the synthesis and structural characterization of manganese carbene complexes. The synthesis of dimanganese monocarbene complexes [Mn2(CO)9{C(OEt)(heteroaryl)}] was done via the classical Fischer method, and a range of complexes containing heteroaromatic substituents, e.g. 2,2'-bithiophene, thiophene, furan and N-methyl pyrrole, was isolated. These complexes displayed a novel configuration with the carbene ligand in the axial position, in contrast to the equatorial position found for the analogous rhenium compound and other dimanganese complexes known from the literature. The possibility of manipulating the position of the carbene ligand in the binuclear complexes was investigated by a nucleophilic substitution of the ethoxy substituent with an amine substituent. Only aminolysis with small, primary amines such as ammonia and propylamine, proved successful. The propylaminocarbene ligands retained their axial configuration, but a conversion to the more thermodynamically stable equatorially substituted carbene ligands was observed for the complexes [Mn2(CO)9{C(NH2)(heteroaryl)}], while mixtures of the equatorial and axial isomers were observed in solution. Structural X-ray analysis proved that although the equatorial position is more electronically favourable, steric hindrance by the second manganese pentacarbonyl moiety prevented ethoxy- and propylamino-substituted carbene ligands to adopt this configuration. A kinetic study of the aminolysis reaction was done in an effort to elucidate the reaction mechanism and to explain the axial-equatorial conversion. Due to the competing decomposition reaction of the product and reagent complexes with that of the substitution reaction, no information about reaction intermediates could be obtained. The target mononuclear complexes [Mn(CO)4{C(OEt)(heteroaryl)}X] (X = Br, I) was obtained by cleavage of the metal-metal bond of the binuclear precursor complexes. Cleaving of the Mn-Mn bond was done oxidatively by halogens, without affecting the carbene ligand. The product complexes have an assembly resembling that of the Grubbs ruthenium metathesis catalyst. Interestingly, the cleaved complexes were found to have a cis configuration of the carbene and halide ligand. Copyright 2006, University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. Please cite as follows: Bezuidenhout, DI 2006, Synthesis and Structural Investigations of manganese carbene complexes, MSc dissertation, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-02122007-120832 / > / Dissertation (MSc)--University of Pretoria, 2007. / Chemistry / unrestricted

An investigation of ferromagnetism in nickel manganese alloys up to forty atomic percent manganese has been carried out. Twenty alloys within this composition range were subjected to three heat treatments such that the conditions within the alloys varied from atomic disorder to a high degree of long range order. The degree of order of Ni₃Mn calculated from measured saturation magnetisation using the Ising model of ferromagnetism was consistent with the value calculated from the ratio of measured integrated intensity of the (110) x-ray diffraction superlattice line to that of line (111). The relationship between saturation magnetisation and concentration for the disordered alloys can be explained adequately by the existence of short range order. A value of 3.4 Bohr magnetons was obtained for the effective magnetic moment of manganese atoms in a nickel lattice. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The Néel temperatures of both the hydrated and 96% deuterated single crystal specimen of antiferromagnetic manganese chloride, have been compared. The sample was placed in the tank circuit of a radio-frequency oscillator; the inductance of the coil and hence the frequency of oscillation thus depended on the susceptibility of the specimen. As the crystal in the liquid helium bath was warmed through the Neel temperature, the oscillation frequency was monitored by a frequency counter. By this method, the Neel temperature could be deduced to change by -2.3% when the crystal was 96% deuterated. This result is comparable to the measurements on CoCl₂.6H₂O and CuCl₂.2H₂O. A semi-quantitative explanation proposes an intimate relationship between the superexchange interaction and the hydrogen bond strength. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

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