Synthesis, Reactivity, and NMR Trends of Early Transition Metal Compounds

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(≡C^tBu)(O^tBu)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(≡C^tBu)(O^tBu)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.