Date of Award

7-2001

Degree Type

Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

Supervisor

Dr. Michael J. McGlinchey

Abstract

This thesis describes the synthesis, characterisation and molecular dynamics of several series of new arene-metal and cationic organometallic complexes, and the potential utility of these systems in synthesis. The first characterised organometallic complexes of trindane (the condensation trimer of cyclopentanone, and a potential synthetic precursor to the unknown molecule sumanene), are reported, and the possibility of derivatising trindane at the benzylic sites is discussed. The X-ray crystal structures of three trindane complexes reveal that sterically demanding groups affect the conformations of the cyclopentene rings. A series of hexaethylbenzene (HEB)-Ru complexes was investigated with respect to their HEB ligand conformations and dynamics in solution. The conformational versatility of HEB allowed a means of probing the stereochemistry and dynamics of these complexes, which were characterised by NMR spectroscopy and X-ray crystallography. A by-product of one reaction, the known complex trans -RuCl2 (PMe3 )4 , was found; the previously unreported X-ray crystal structure of this compound is described. The ideas of Bürgi and Dunitz (that a succession of static X-ray structures can provide information about the dynamics of a reaction) have been applied to finding the migration pathway of a CR2+ moiety in a series of bimetallic cluster cations, [Cp2 Mo 2 (CO)4 (HC=C-CR2 )]+ , from one molybdenum vertex to the other. The construction of an energy hypersurface for the migration of a C=CH2 fragment over a [Cp2 Mo2 (CO) 4 CH]+ triangular base reveals that the structure whereby the CH2 group is oriented directly over a metal vertex lies at the bottom of the potential energy well. The calculated migration trajectory between vertices is beautifully paralleled by a series of X-ray crystal structures of cations [Cp2 Mo2 (CO)4 (RC≡C-CR ' R'' )]+ . In dicobalt clusters, the preference of an alkynyl dicobalt hexacarbonyl moiety to occupy an equatorial position in ring systems has been extended to several alkynylcyclohexanols. The alkynol conformations are compared with the structures of the corresponding Co2 (CO)6 complexes, including structures where the Cot cluster competes with a tert -butyl group for an equatorial site. A mechanism involving migration of a carbocationic centre between cobalt vertices in a cluster is rationalised in light of these results.

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