Synthesis and Reactivity of PtII Complexes with Secondary Sphere N-H Moieties
Zahora, Braden Andrew
MetadataShow full item record
Direct transformations of abundant hydrocarbons into higher valued products would circumvent energy intensive processes, reforming the chemical industry. Late transition metals, particularly platinum, are known to selectively convert alkanes into functionalized products. However, a practical method with an economically viable oxidant has yet to be discovered. New methods for alkane activation may yield further advances towards this goal. This dissertation focuses on how platinum methyl complexes with ligand-based protons can form methane, the microscopic reverse of methane activation. Chapter 1 provides an introduction on the need to develop new methods to functionalize hydrocarbons. Furthermore, a survey of the literature with respect to how late metal complexes can undergo productive reactivity with substrates which are deemed necessary for practical alkane partial oxidation is presented. Chapter 2 focuses on the synthesis and reactivity of 5-(6-methyl-2-pyridyl)-3-tert-butylpyrazolate (NNMe) and 2-(5-tert-butylpyrazol-3-yl)-6 (diethylaminomethyl)pyridine (NNNEt) ligated PtII complexes. Once formed, conditions necessary for methane formation were found and it was determined that the ligand-based N-H was not involved in methane formation. Chapter 3 explores synthesis and reactivity of 5-tert-butyl-1,3-bis(pyrazol-3-yl)pyridine (NNN) and 5-tert-butyl-1,3-bis(pyrazol-3-yl)benzene (NCN) ligated PtII-alkyl complexes with electrophilic reagents. It was found that tridentate ligated pyrazolate PtII-R systems can undergo protonation at the ligand if there is a weak pyridine trans donor (vs strong phenyl trans donor) to the PtII-R moiety. However, reactivity with methyl iodide occurred at the metal first, with further ligand methylation spectroscopically observed for the NNN ligated Pt-CH3 complex. Chapter 4 discusses the synthesis and characterization of bis(phosphino)amine ligated PtII complexes, which contained a ligand-based N-H. Taking advantage of unfavorable steric congestion of bulky Ph groups on the ligand, methane formation was observed from thermolysis reactions of a bis(phosphino)amine ligated Pt(CH3)2. Although additional characterization of the resulting metal-containing product is required, it appears that methane was formed through cooperation of the ligand-based N-H moiety and the Pt-CH3 ligand.
- Chemistry