Date of Award
Doctor of Philosophy
Michael Best, Craig Barnes, Hong Guo
This dissertation focuses of three different subjects. The first is the synthesis and characterization of heptacoordinate amidinate compounds. Heptacoordinate compounds are not common, but their structures have been studied. Group 4 amidinate compounds have been used as precursors in the CVD/ ALD processes. Ancillary ligands, such as amidinates, have been used to reduce air-sensitivity of complexes. Reactions of these complexes with water have been used to make metal oxide thin films.
In the first study, the complexes Zr[MeC(NiPr)2]3Cl [zirconium trisamidinate chloride], Hf[MeC(NiPr)2]3Cl [hafnium trisamidinate chloride], Zr[MeC(NiPr)2]3Me [zirconium trisamidinate methyl], Hf[MeC(NiPr)2]3Me [hafnium trisamidinate methyl], Zr[MeC(NiPr)2]3Et [zirconium trisamidinate ethyl], and Hf[MeC(NiPr)2]3Me [hafnium trisamidinate methyl] have been synthesized and characterized. The three amidinate ligands bind to the metal centers in a propeller-like fashion. This allows for Λ [lambda] and Δ [delta] enantiomers, which undergo fast exchange in solution. All of these complexes were also found to react with water in air to form Zr[MeC(NiPr)2]3OH [zirconium trisamidinate hydroxyl] or Hf[MeC(NiPr)2]3OH [hafnium trisamidinate hydroxyl] complexes.
The second portion of the dissertation focuses on the reactions of tungsten alkylidyne complexes with water. When W(≡CSiMe3)(CH2SiMe3)3 [tungsten neosilyl neosilylidyne] is reacted with water at room temperature, a tungsten trimer was formed and characterized via NMR spectroscopies and single-crystal X-ray diffraction. The reaction of a second complex, W(≡CtBu)(OtBu)3 [tungsten alkoxide neopentylidyne] with water was studied via NMR and mass spectrometries. While only one complex formed via the NMR-scale reactions, several more were identified using the DART ionizer to react W(≡CtBu)(OtBu)3 [tungsten alkoxide neopentylidyne] with water in air before being analyzed via MS.
The last subject focuses on the chemical shift trends of d0 [d0] metal complexes. Two trends have been identified and will be discussed in Part 5. The first trend, usually pertaining to hydride and alkyl complexes, is a downfield shift in the peaks of the a [alpha] atoms in first- and third-row metals from those of the second-row analogs. The first trend, which usually relates to alkylidene, alkylidyne, oxo, and fluoro complexes, is an upfield shift in the peaks of the a atoms in first- and third-row metals from those of the second-row analogs.
Cook, Tabitha Marie, "Synthesis, Reactivity, and NMR Trends of Early Transition Metal Compounds. " PhD diss., University of Tennessee, 2016.