Date of Award


Publication Type

Doctoral Thesis

Degree Name



Chemistry and Biochemistry


Pure sciences, Cobalt complexes, Dehydrotropylium


James Green




Despite a large amount of information on the application of Nicholas reactions in organic syntheses, little attention has been paid to the structural variation of cationic intermediates and the factors that may influence reactivities and stabilities of these species.

The primary focus of this project was to design and generate a new type of Nicholas carbocation that possesses multiple sources of stabilization. For this matter, nominally aromatic cation 99 was chosen as the target compound. The effects of resonance stabilization on the stability and reactivity of the cation 99 were investigated both experimentally and by means of computational calculations. From reactivity studies of cation 99, a sharp switching of reaction pathway from electrophilic addition to dimerization was observed for the nucleophiles with N <1. Non-aromatic, highly conjugated acyclic cation 127, was prepared as structural model and its reactivities in Nicholas reactions were investigated for comparison purposes. From experimental and computational studies cation 99 was found to be weakly aromatic with its NICS (1) value approximately 28% of tropylium ion.*

Preliminary attempts were made to prepare the precursor to the benzo-fused derivative of dehydrotropylium cation (100). This has led to the formation of phosphonate substituted benzo-fused dehydrotropone ( 151). The scope and limitations of the method for synthesis of other Co2(CO)6-complexes of substituted benzo-fused dehydrotropone (152 and 153) were further investigated.*

*Please refer to dissertation for diagrams.