02/25/19 - 4:00 PM to 5:00 PM
Special Seminar: Professor Bradley P. Carrow
Leveraging Polarizability and Electrophilicity in Catalysts for Challenging Coupling Reactions
A general approach by our group for the development of new catalytic synthetic methods that occur with higher efficiency and selectivity, use simpler reagents, and proceed with lower energy demand involves new ancillary ligand design coupled with fundamental studies of how metal-ligand bonding dictates catalytic reactivity. In this context, the presentation will focus on our recent efforts to discover new phosphorus- and sulfur-based ligands and associated metal catalysts that manifest special properties from seemingly “weak” interactions, for instance dispersion. In one case, low-coordinate Pd complexes possessing polarizable diamondoid substituents are shown to enable a new transmetalation mechanism under exceptionally mild conditions, facilitate the first ever characterization and reactivity studies of monoligated Pd(0) – the true active catalyst in modern cross-coupling reactions, and direct visible light-induced bond weakening. Studies of oxidative dehydrogenative coupling reactions will also showcase evidence for a distinct C−H bond activation mechanism that we describe as electrophilic CMD or “eCMD”, which has characteristics distinct from the established concerted metalation-deprotonation (CMD) pathway for C−H functionalization. Transition state analyses suggest this reaction pathway could be a general class of C−H activation that to date has been convoluted with CMD, and selection rules have been identified for predicting what catalyst structures manifest either classic CMD or eCMD, each of which occurs with characteristic substrate preferences and selectivity.
Bradley Carrow is a professor in the Department of Chemistry at Princeton University. Previously he was a professor at the University of Tokyo, and a post-doctoral fellow with Kyoka Nozaki at the University of Tokyo. He earned his doctorate with Professor John Hartwig at the University of Ilinois at Urbana-Champaign, and his bachelor's degree in chemistry at the Missouri University of Science and Technology.
A main focus of Professor Carrow's lab is the mechanism-driven design of homogeneous transition metal catalysts for the synthesis of materials and biologically-relevant small molecules. His recent efforts have centered around complexity building from feed stock chemicals and integrating greener reagents to improve the sustainability of synthetic methods. Embracing the power of ancillary ligands to modulate the lifetime, reactivity, and selectivity of metal catalysts, his core approach involves an iterative cycle of mechanistic studies to establish new catalyst structure-function relationships that inform rational ligand evolution.