@article{THESIS,
      recid = {1422},
      author = {Vibbert, Hunter Baksa},
      title = {Group 6 Metal-Oxo and -Alkylidyne Complexes with High  Reactivity Derived from π-Antibonding Orbitals},
      publisher = {University of Chicago},
      school = {Ph.D.},
      address = {2018-12},
      number = {THESIS},
      pages = {336},
      abstract = {Photoredox catalysis has become a useful synthetic  technique to make and break chemical bonds in chemical  structures relevant to medicinal chemistry and renewable  energy. Few general approaches, however, have been reported  that can prepare synthetically useful organic radicals  whose parent molecules are reduced negative of –2.6 V (vs  FeCp20/+). One such approach to accessing these molecules  is to design photoredox chromophores that can directly  prepare these radical species. The central hypothesis  investigated here is that the electronic structure of  tungsten-alkylidyne (or benzylidyne) complexes lends them  to serve as highly reducing, visible-light  photoreductants.

	This work describes the  electronic-structure description, optimization of synthetic  routes, excited-state characterization, and net reactions  of tungsten-alkylidyne complexes of the general form  W(CAr)L4X (Ar = aryl, L = bidentate phosphine, X =  halide/pseudo-halide).    First, we elaborate the general  synthetic routes to these complexes for the purpose of  electronic-structure design. The electronic-structure  design was accomplished via Density Functional Theory (DFT)  with experimental correlations. This was used to design  highly reducing tungsten photoredox catalysts. The  photophysics of these complexes were studied to assess  their reactivity as photoredox chromophores, and the  experimental room temperature measurement of the  excited-state oxidation potentials for two tungsten  derivatives demonstrated the highly reducing nature of  these complexes. Finally, net photoredox reactions were  explored. Among those were the C–H arylation of  difficult-to-reduce aryl halide (I, Br, and Cl) molecules.  These reactions could be affected using low chromophore  loadings and a simple industrially relevant base. 

	A  second conceptually related project stemmed from the  observation that some of the electrochemical first  reduction potentials of a series of molybdenum(IV)-oxo  complexes of the general type, [Mo(O)L4X]+ were reversible.  We were able to isolate and study an unusual example of a  low-spin d3 molybdenum-oxo complex via single-electron  reduction. This complex was observed to possess an  elongated bond relative to the d2 redox congener by single  crystal X-ray crystallography that could be corroborated by  vibrational spectroscopy and DFT.},
      url = {http://knowledge.uchicago.edu/record/1422},
      doi = {https://doi.org/10.6082/uchicago.1422},
}