Spring 2022

Wednesday, January 5 @ 2 pm 

Mr. Steven Rehbein will defend his PhD in Chemistry beginning with a seminar titled "Catalysis with Early and Late Transition Metals: C—H Activation at Tantalocene Hydrides and Oxidative Addition at Palladium Solvato Complexes."

Abstract: Herein we present our work on transition metal catalysis using metals from two sides of the periodic table: C—H activation catalyzed by early transition metals and cross-couplings catalyzed by late transition metals. In the first part,  a synergistic experimental and computational approach was employed to investigate the possibility of extending the reactivity of bent tantalocene hydrides beyond aromatic C—H activation to enable activation of aliphatic substrates. In situ monitoring of the characteristic 1H NMR metal hydride signals in the reaction of Cp2TaH3 and related complexes with deuterated aromatic substrates allowed for the evaluation of reaction kinetics of catalyst decomposition, H/D exchange, and off-cycle reactions. The insight gained from in situ reaction monitoring with aromatic substrates, combined with computational analyses, allowed for the extension of this chemistry to intra- and intermolecular aliphatic C—H activation. This work represents the first example of aliphatic C—H activation by homogeneous tantalum hydrides. In the second part, we provide compelling evidence that solvent coordination to palladium during oxidative addition of chloroaryl triflates can result in an inversion of chemoselectivity of this step. Previous investigations attributed a solvent-dependent switch in chemoselectivity to the propensity of polar solvents to stabilize anionic transition states of the type [Pd(PtBu3)(X)]- (X = anionic ligand). However, our detailed investigations show that solvent polarity alone is not a sufficient predictor of selectivity. Instead, solvent coordinating ability is selectivity-determining, with polar coordinating and polar noncoordinating solvents giving differing selectivity, even in the absence of anionic ligands "X". A solvent-coordinated bisligated transition state of the type Pd(PtBu3)(solvent) is implicated by density functional theory calculations. This work provides a new mechanistic framework for selectivity control during oxidative addition.

Advisor: Prof. Sharon Neufeldt

Byker Auditorium or WEBEX

Thursday, January 13 @ 9:30 am 

Mr. Elias Pomeroy will defend his PhD in Chemistry beginning with a seminar titled "Operando Optical and Quantitative Electrochemical Studies of Solid Oxide Fuel Cell Anode Degradation and Regeneration." 

Abstract:

Solid Oxide Fuel Cells (SOFCs) are high temperature (600-1000 °C) devices which can generate electricity from a wide variety of fuels at extremely high efficiencies. Unfortunately, SOFC anodes are susceptible to gas phase contaminants, especially sulfur, and graphitic carbon formation. Additionally, the extreme operating conditions of SOFCs make studying their chemistries challenging. This presentation will explore new quantitative electrochemical methodologies and operando optical to study degradation and remediation of SOFC anodes. First, since typical electrochemical techniques infer microstructural changes rather than directly measuring surface area, a traditional electrochemical technique, chronocoulometry (CC), was adapted to SOFCs for the first time to measure the electrochemically active area of the anode. This technique showed that active area is temperature dependent, that sulfur poisons SOFC anodes in a more complex manner than simply blocking active sites, and carbon monoxide decreased the number of active sites. Next, operando thermal imaging, in combination with mass spectrometry, Fourier transformed infrared emission spectroscopy, and electrochemistry explored different methodologies of carbon remediation, comparing electrochemical oxidation, molecular oxygen, and steam as methods to remove graphite accumulated on SOFC anodes. This study found that with all methods, CO2 played a key role in removing carbon, that both electrochemical oxidation and steam removed carbon more globally than oxygen, and that imaging the entire cell is key to understanding the complex chemistry occurring on SOFCs.

Advisor: Prof. Rob Walker

Byker Auditorium and or WEBEX 

Friday, January 21 SPECIAL TIME @ 8 am  

Prof. Cornelia Welte (Radboud University, Nijmegen)

Host: Prof. Roland Hatzenpichler

WEBEX only

Friday, January 28 - OPEN

Friday, February 4 - OPEN

Friday, February 11 - OPEN

Friday, February 18

Prof. Uttam Tambar (UT- Southwestern)

Host: Prof. Matt Cook

Friday, February 25 

Hunter Fausset 4th year graduate student seminar in biochemistry. 

Advisor: Prof. Brian Bothner 

Friday, March 4 

Prof. Kim See (Caltech) 

Host: Prof. Nick Stadie

Friday, March 11

Dr. Benedikt Geier (Postdoc, Stanford University) will present "Spatial Metabolomics of in situ Host–microbe Interactions at the Micrometre Scale."

Host: Prof. Roland Hatzenpichler

Friday, March 18 SPRING BREAK

Friday, March 25

Graduate Student Seminar in Biochemistry. Stephanann Costello 

Co-advisors: Profs. Valerie Copie and Frances Lefcort 

Friday, April 1

Prof. Kristopher Waynet (Univ. of Idaho)

Host: Prof. Matt Cook

Friday, April 8 

Graduate Student Seminar in Chemistry - David Stephens

Advisor: Prof. Michael Mock

Friday, April 15 NO CLASSES

Friday, April 22

Prof. Gojko Lalic (Univ. of Washington)

Host: Prof. Matt Cook

Friday, April 29

Prof. Jeff Bandar (Colorado State)

Host: Prof. Matt Cook

Friday, May 6 

Prof. Gary Molander (U-PENN)

Host: Prof. Sharon Neufeldt