The search for hypercloso metallacarboranes through ligand manipulation
Jones, John J.
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Chapter one is an introduction to carborane and metallacarborane chemistry, with a particular focus on “non-Wadian”, including hypercloso, heteroboranes. The chapter then discusses the various methods that could be used to synthesise hypercloso boranes and heteroboranes before identifying generating hypercloso metallacarboranes through ligand set manipulation as the objective of this project. Chapter two contains a discussion of attempts to synthesise hypercloso molybdacarboranes through ligand abstraction. A reaction between the species [NEt4][1,7-Me2-2,2,2-(CO)3-2-I-closo-2,1,7-MoC2B9H9] and Ag[BF4] was found unexpectedly to regenerate 1,7-Me2-2,2,2,2-(CO)4-closo-2,1,7-MoC2B9H9 through a process referred to as carbonyl stealing. Further related experiments also produced results consistent with carbonyl stealing. In chapter three efforts are instead directed at synthesising hypercloso ruthenacarboranes. In the process two new routes to closo ruthenacarboranes were developed. The first leads to anions of the general formula [1,2-R2-3-Cl-3,3-(PPh3)2-closo-3,1,2-RuC2B9H9]- whilst the second (which follows from this) was used to synthesise a diverse family of mixed ligand ruthenacarboranes. Attempts to synthesise hypercloso ruthenacarboranes instead produced highly complex product mixtures from which several unusual “wedged” species were isolated. Chapter four describes efforts directed towards synthesising hypercloso ruthenacarboranes using the same methodology as in chapter three but by also exploiting steric factors. This once again resulted in complex product mixtures from which some highly unusual species were isolated, including an additional “wedged” species as well as two “symbiotic” species, one of which is without precedent in the literature. Chapter five contains a summary of the research contained within this thesis whilst chapter six contains experimental details for all of the novel compounds prepared as well as alternative or improved syntheses for some literature compounds.