The reactions of methyl-substituted chlorocyclotriphosphazenes with aryl Grignard reagents and with bifunctional amines, aminoalcohols, and alkoxides were investigated. The characterization data for the compounds formed in the reactions of monomethylpentachlorocyclotriphosphazene and the Grignard reagents were found to be informative with respect to the extent and nature of the interaction between the phosphazene ring and its exocyclic substituents. This interaction was found to be responsible for significant effects on the reactions of the phosphazene ring with nucleophiles. The reactions of the bifunctional nucleophiles were found to be useful probes of the reactivity of the phosphazene ring. Specifically, a single methyl group is found to activate the chlorine on the same phosphorus atom, while a pair of geminally substituted methyl groups is found to deactivate the chlorine atoms on a different phosphorus atom. The results allow a new interpretation of the substitution patterns of various nucleophiles on chlorocyclotriphosphazenes. / Ph. D. / incomplete_metadata