Doctor of Philosophy (PhD)



Document Type



The conversion of olefins to aldehydes represents an important chemical transformation that can be exploited to generate a wide range of products from the hydroformylation process. The aldehydes produced via hydroformylation are often converted to additional value-added products. This process is typically catalyzed by monovalent rhodium or cobalt complexes. Industrially, rhodium complexes have become increasingly popular due to their high activity and tolerance to bidentate phosphine and phosphite ligands. Developing a competitive cobalt catalyst is of interest to drive down the cost of the catalytic system.

Recently, a cationic Co(II) precatalyst was reported to perform hydroformylation with activity within an order of magnitude of Rh(I) systems. This report, however, would later be contested as Zhang et al. could not replicate the results. The [Co(acac)(dppBz)]BF4 precatalyst in question was investigated further. First, the characterization of the complex was more thoroughly investigated by ESI-TOF mass spectrometry. The previously unappreciated impurity, Co(acac)2(dppBz), was identified and quantified by ESI-TOF MS, and subsequently removed via synthetic modification. Pure [Co(acac)(dppBz)]BF4 was shown to be an effective hydroformylation precatalyst. Adding Co(acac)2(dppBz) impurities to [Co(acac)(dppBz)]BF4 in situ resulted in less hydroformylation activity. In addition, the hydroformylation activity of [Co(acac)(dioxane)4]BF4 was studied and determined to be a more flexible platform exhibiting enhanced activity with substoichiometric equivalents of dppBz. [Co(acac)(dppBz)]BF4 was also iterated on further by attempting to replace the acac with a monodentate alkoxide to promote the activation of the precatalyst. Co(OiPr*)2(dppBz) was synthesized, but the protonolysis to generate the desired precatalyst [Co(OiPr*)(dppBz)]BF4 remains a challenge.

Traditionally, CO/ethylene copolymerization proceeds via a near perfect alternation of CO and ethylene catalyzed by a cationic Pd, Rh, or Ni catalyst. Disrupting this perfect alternation is an area of active interest due to the high melting of polyketones (257 oC), which is driven by the strong interchain interactions of the polar carbonyls. Disrupting this interaction by the double insertion of CO has remained elusive in the literature. Introducing germylene ligands could promote this by trapping the metal–acyl intermediate through π-activation of the carbonyl. A PGeP-typepincer ligand was synthesized and coordinated to Pd through treatment of PGeP with Pd(PPh3)4.



Committee Chair

Chambers, Matthew B.

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