Warren Piers (University of Calgary) Seyferth Lectureship in Organometallics

4-370

Molybdenum Complexes for Ammonia Activation: Mechanisms of Hydrogen Production and N-N Bond Formation.Abstract: Ammonia oxidation catalyzed by molecular compounds is of current interest as a potentially carbon free source of dihydrogen. Two key processes in this complex reaction are the activation of N-H bonds through coordination induced bond weakening at transition metal centers and N-N bond formation from various MNHn (n = 0-2) intermediates. In this talk, published work on the substantial N-H bond weakening and dihydrogen loss from coordinated ammonia in low valent Mo complexes of a diborate pentadentate ligand system will be briefly summarized. The remainder of the talk will focus on recent work aimed at defining the factors that encourage N-N bond formation via coupling of higher valent terminal nitrido complexes of this ligand system. We provide evidence for an extremely facile, oxidation induced ambiphilic coupling to release dinitrogen from these species and will detail other intriguing reactions of highly electrophilic cationic nitrido intermediates. The relationship of this chemistry to catalytic ammonia oxidation schemes will also be emphasized.Refreshments will be served outside of 4-370 at 4PM.