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Title: Metallacarboranes derived from 1,1′-bis(o-carborane)
Author: Mandal, Dipendu
ISNI:       0000 0004 6347 5759
Awarding Body: Heriot-Watt University
Current Institution: Heriot-Watt University
Date of Award: 2016
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Chapter one gives an overview of single cage heteroborane chemistry, particularly the areas of 12- and 13-vertex metallacarboranes and their isomerisations. Also included is the chemistry of bis(carboranes), with recent developments on chelating derivatives of 1,1'-bis(o-carborane), as well as reduction/metallation of bis(o-carborane). Chapter two describes metallation of the [7-(1′-1′,2′-closo-C2B10H11)-7,8-nido- C2B9H10]2– dianion with various {NiPP}2+, {PdNN}2+ or {NiP2}2+ fragments (PP = chelating diphosphine; NN = chelating diamine; P = monodentate phosphine or phosphite) and which leads either to unisomerised 3,1,2-MC2B9 species or to isomerised 4,1,2-MC2B9 or 2,1,8-MC2B9 species, all with a pendant C2B10 substituent. The products were fully characterised spectroscopically and crystallographically as appropriate. Overall the results suggest that an important factor in a 3,1,2 to 4,1,2 isomerisation is the relief gained from steric crowding, whereas a 3,1,2 to 2,1,8 isomerisation appears to be favoured by strongly electron-donating ligands on the metal. Chapter three describes capitation of the [7-(7′-7′,8′-nido-C2B9H10)-7,8-nido-C2B9H10]4– tetraanion with {NiPP}2+ and {BX}2+ fragments (PP = chelating diphosphine; X = Br, I, Ph). This results in examples of MC2B9-MC2B9 architectures (3′,1′,2′-3,1,2; 4′,1′,2′-3,1,2) or bis(carborane) derivatives. Thermal isomerisation of the bis(nickelacarboranes) is studied. Unexpected interconversion is observed between bis(nickelacarborane) diastereoisomers (rac and meso isomers of 3′,1′,2′-NiC2B9-3,1,2-NiC2B9) ligated by dmpe and the mechanism of this interconvesion is considered. A stereospecific product was observed in the nickelacarborane ligated by dppe and this is rationalised by DHB. Formation of 4′,1′,2′-NiC2B9-4,1,2-NiC2B9 and 2′,1′,8′-NiC2B9-4,1,2-NiC2B9 isomers on thermolysis of 3′,1′,2′-3,1,2 or 4′,1′,2′-3,1,2 MC2B9-MC2B9 precursors is elucidated in terms of DHB. Finally a new naming convention is introduced for these 12-vertex/12- vertex bis(nickelacarboranes) to distinguish the chirality between cages. Chapter four elaborates the thermolysis of a rac/meso mixture of the species [1-(1′-4′-Cp- 4′,1′,6′-closo-CoC2B10H11)-4-Cp-4,1,6-closo-CoC2B10H11] to yield a rac/meso mixture of [1-(1′-4′-Cp-4′,1′,12′-closo-CoC2B10H11)-4-Cp-4,1,12-closo-CoC2B10H11]. Cage carbonatom identification is accomplished by both the VCD and BHD methods. Polyhedral expansion of the rac and meso isomers of 4′,1′,12′-CoC2B10-4,1,12-CoC2B10 was also attempted targeting 14-vertex metallacarborane/14-vertex metallacarborane derivatives. Chapter five contains the experimental procedures leading to, and characterisation details for, all new compounds reported herein. Crystallographic data is listed in the Appendix together with structure solution and refinement details.
Supervisor: Welch, Alan J. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available