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Title: Novel {1,2-closo-C2B10} carbaborane compounds
Author: Reid, Bruce D.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1992
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Chapter 1 outlines the development of carbaborane and carbametallaborane chemistries and is consequently background to the work described in this thesis. Brief descriptions of the chemistry and bonding capability of the tertiary gold(I) fragment and of chemical studies related to BNCT are also presented. Chapter 2 describes the synthesis and characterisation of a series of σ-bonded phosphine and arsine gold(I)carbaborane compounds, 1-R'-2-(ER_3Au)- 1,2-closo-C_2B_10H_10 (R' = Ph [3] or CH_3OCH_2 [4], ER_3 = PPh_3 [a], P(o-tol)_3 [b] PCy_3 [c], Pet_3 [d] or AsPh_3 [e]) by reaction between ER_3AuCl and the appropriate lithium carbaborane. The ^11B(^1H) NMR spectrum of 1-CH_3OCH_2-2-(PPh_3Au)-1,2-closo-C_2B_10H_10 (4a) is assigned by an ^11B-^11B COSY NMR experiment and by comparison with the (assigned) ^11B(^1H) NMR spectrum of 1-CH_3OCH_2-1,2-closo-C_2B_10H_11 (1). Consideration of the ^11B(^1H) NMR and (where appropriate) ^31P(^1H) NMR chemical shifts of compounds 3 and 4 by comparison with related species implies that the closo-carbaborane ligands function as efficient electron donating groups. Comparison of the Au-C distance in 1-CH_3OCH_2-2-(AsPh_3Au)-1,2-closo-C_2B_10H_10 (4e and AsPh_3AuMe (5) suggests that the gold-carbon bond in the former is stronger. This is supported by analysis of the results from EHMO calculations on model compounds. Consequently, closo-carbaboranes bonded to metal atoms via a metal-carbon σ-bond are shown to be good σ-donor ligands. Chapter 3 discusses the synthesis and characterisation of thermally stable σ-bonded titanium(IV) carbaborane compounds by reaction of TiCl4 or CpTiCl3 with lithium carbaborane. Reaction of Cp2TiCl2 with one or two equivalents of lithium carbaborane yielded the decomposition product Cp2TiCl (9), though the latter reaction afforded a transient deep green species which is tentatively suggested as being a titanocene carbaborane compound. The molecular structure of 1-CH3OCH2-2-(CpTiCl2)-,1,2-closo-C2B10H10 (8) was determined by X-ray crystallography and the TiIV centre was found to be 7-coordinate as a result of intramolecular coordination by the oxygen atom of the substituent ether group. Comparison of the 11B(1H) and 1H NMR spectra of 1-CH3OCH2-2-(TiCl3)-1,2-closo-C2B10H10 (6) and 8 allows the structure of the 6 to be proposed.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available