טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentKatz Liron
SubjectStudies on the Reactivity of N-X bonds (X=O, BR, Cl)
with Transition Metals
DepartmentDepartment of Chemistry
Supervisor Professor Mark Gandelman
Full Thesis text - in Hebrew Full thesis text - Hebrew Version


Abstract

Elementary transition metal - mediated reactions that cleave and form the bonds of organic molecules are among the fundamental steps in catalysis. Such bond cleavage and formation often occurs by oxidative addition and reductive elimination. Based on principle of microscopic reversibility, these two reactions represent the reversible processes. The term oxidative addition confers no information about the mechanism of the reaction. Majority of catalytic cycles based on late transition metals include this important step. For example, metal - mediated coupling reactions of C-C, C-H and C-heteroatom bonds involve bond activation event in substrate. Many palladium-catalyzed processes include this step and represent a frequently applied reactions which increasingly being employed in synthetic routes to complex biological targets and therapeutic agents.

Organic compounds containing N-X bond represent a very interesting and important class of reagents in synthetic chemistry. For example hydroxylamines are broadly utilized as electrophilic aminating agents due to reverse polarizability of N-O bonds. In addition, N-Br or N-Cl containing compounds have found diverse applications in synthesis by delivering a halogen and / or nitrogen based units to the target molecule.

Despite of their wide use in organic chemistry the reactivity of this class of compounds with organometallic complexes were practically not studied.

There are very few examples of N-halide bond activation by transition metals. Moreover, to the best of our knowledge, the well defined metal insertion into N-O bond is unprecedented. Numerous transformations based on this crucial step tend to believe that the mechanism involves an oxidative addition of N-O bond, but the corresponding intermediate has been not isolated. 

From synthetic point of view, we presume that the selective activation of N-X bonds by transition metals will lead to a fast development of molecular complexity of organometallic species and will open a door to the discovery of new useful catalytic transformations.

In this work we present a reactivity of N-X bond ( X = O, Br, Cl ) containing compounds with Pd(0), Rh(I) and Pt(0) complexes. Selective activation of these bonds, including the first example of N-O oxidative addition to Pd and Pt, characterization and chemistry of the resulting compounds are discussed.  Moreover a progress towards understanding the mechanism of the oxidative addition in this case is presented.