טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentPogoreltsev Alla
SubjectNitrogen Lewis Acids
DepartmentDepartment of Chemistry
Supervisor Professor Mark Gandelman
Full Thesis textFull thesis text - English Version


Abstract

Lewis acids and their interactions with Lewis bases are among the most fundamental aspect of chemistry. Although many chemical elements can serve as central atom of Lewis acids, nitrogen-centered compounds are usually considered as Lewis bases due to their lone pair of electrons having relatively high energy. Recently, our group demonstrated that N-heterocyclic nitrenium ions can coordinate to various transition metal centers, possessing a Lewis basic feature. The availability of vacant pp-orbital of nitrenium species suggests that it also might be involved in s-interactions with Lewis bases, possessing a Lewis acidic character. Here we present the first examples of reactivity of nitrenium species towards Lewis bases. This represents a first example of robust, stable and stereoelectronically modifiable nitrogen Lewis acids, which form well-defined adducts with Lewis bases. This reactivity provides a new type of stable organic compounds, called triazanes, bearing all-saturated three consecutive nitrogen atoms. Moreover, we demonstrate the reactivity of some adducts. 2-H-triazane represents unique for amines umpolung reactivity of the N-H bond, possessing both protic and hydridic character. The ability of nitrenium species to act as Lewis acids was explained by theoretical calculations. In addition, we present the first example of intramolecular system, in which nitrenium Lewis acid and phosphine Lewis base forms weak internal interaction.