UVM Theses and Dissertations
Format:
Print
Author:
Leshinski, Sarah
Title:
Dept./Program:
Chemistry
Degree:
MS
Abstract:
The preparation of new element-element bonds, either stoichiometrically or catalytically, has demonstrated widespread use in all areas of chemical research. This thesis describes the versatility of triamidoamine-supported zirconium complexes that affect such transformations. A novel triamidoamine-supported zirconium complex, [K⁵_ N, N, N, N, C-(Me₃SiNCH₂CH₂)₂NCH₂CH₂NSiMe₂CH₂]Zr (1), is capable of affecting a wide range of reactivities. The triamidoamine ligand can bind to metals in oxidation states 3+ and higher, making it is a desirable ancillary ligand. Furthermore, its straightforward and inexpensive synthesis allows for production on a large scale.
It is advantageous to develop synthetic methods capable ofaffording new carbonphosphorus bonds as they have demonstrated prevalent use in areas such as chemistry, biology, and materials. Catalytic intermolecular hydrophosphination reactions were accomplished to afford such transformations. Complex 1 had previously been used in hydrophosphination reactions based on insertion reactivity involving a reported complex, (N₃N)ZrPPh₂ (2). As a new contribution to the project, insertion reactions and hydrophosphination reactions were accomplished involving carbodiimide substrates yielding phosphaguanidine products. Similaryly, small-molecule substrates were found to insert into the Zr-C bond of 1 via 1,1-or 1,2-insertion modes, affording products containing new zirconium-carbon, zirconium-nitrogen, or zirconium-oxygen bonds. Each reaction demonstrated a loss of symmetry from 1, as the metallocycle was expanded to incorporate a new substrate. These preparations are useful in various catalyses, nitrogen-fixation reactions, and synthetic methods.
This thesis describes further reactivity of 1, and for the first time, 1(Et₂O) was characterized by X-ray crystallography. This characterization was highly desired as 1 is the focus of research in the Waterman group. Reaction of 1 with hydrogen gas yielded a desired hydride complex, (N₃N)ZrH (18), previously predicted to be an intermediate in catalyses involving 1. By the same experimental procedure, the trimethylsilyl protons on the triamidoamine ligand of 1 were gradually exchanged with deuterium atoms upon reaction with deuterium gas to produce [K⁵-N, N, N, N, C-((CD₃)₃SiNCH₂CH₂)₂NCH₂CH₂NSi(CD₃)₂CD₂]Zr (19). Deuterated ligands are particularly useful for paramagnetic complexes. An investigation with para-hydrogen was attempted in order to provide mechanistic insight towards catalyses involving 1, particularly in determining if sigma-bond metathesis was occurring. However, inconclusive results were obtained for this study.
This thesis focuses on the unique reactivities of a triamidoamine-supported zirconium complex. The new bond-forming reactions will be described'herein, along with proposed mechanisms and characterization by NMR and IR spectroscopy, as well as elemental analysis.
It is advantageous to develop synthetic methods capable ofaffording new carbonphosphorus bonds as they have demonstrated prevalent use in areas such as chemistry, biology, and materials. Catalytic intermolecular hydrophosphination reactions were accomplished to afford such transformations. Complex 1 had previously been used in hydrophosphination reactions based on insertion reactivity involving a reported complex, (N₃N)ZrPPh₂ (2). As a new contribution to the project, insertion reactions and hydrophosphination reactions were accomplished involving carbodiimide substrates yielding phosphaguanidine products. Similaryly, small-molecule substrates were found to insert into the Zr-C bond of 1 via 1,1-or 1,2-insertion modes, affording products containing new zirconium-carbon, zirconium-nitrogen, or zirconium-oxygen bonds. Each reaction demonstrated a loss of symmetry from 1, as the metallocycle was expanded to incorporate a new substrate. These preparations are useful in various catalyses, nitrogen-fixation reactions, and synthetic methods.
This thesis describes further reactivity of 1, and for the first time, 1(Et₂O) was characterized by X-ray crystallography. This characterization was highly desired as 1 is the focus of research in the Waterman group. Reaction of 1 with hydrogen gas yielded a desired hydride complex, (N₃N)ZrH (18), previously predicted to be an intermediate in catalyses involving 1. By the same experimental procedure, the trimethylsilyl protons on the triamidoamine ligand of 1 were gradually exchanged with deuterium atoms upon reaction with deuterium gas to produce [K⁵-N, N, N, N, C-((CD₃)₃SiNCH₂CH₂)₂NCH₂CH₂NSi(CD₃)₂CD₂]Zr (19). Deuterated ligands are particularly useful for paramagnetic complexes. An investigation with para-hydrogen was attempted in order to provide mechanistic insight towards catalyses involving 1, particularly in determining if sigma-bond metathesis was occurring. However, inconclusive results were obtained for this study.
This thesis focuses on the unique reactivities of a triamidoamine-supported zirconium complex. The new bond-forming reactions will be described'herein, along with proposed mechanisms and characterization by NMR and IR spectroscopy, as well as elemental analysis.