UVM Theses and Dissertations
Format:
Print
Author:
Roering, Andrew J.
Dept./Program:
Chemistry
Year:
2011
Degree:
PhD
Abstract:
The formation of phosphorus-element bonds has become important in all areas of chemistry including ligand design, therapeutics, and materials science applications. This dissertation describes a novel thrimidoamine-supported zirconium complex [K5-N, N, N, N, C-Me₃SiNCH₂CH₂)₂NCH₂CH₂NSIMe₂CH₂]Zr (1), which has been shown to facilitate several phosphorus-element bond-forming reactions. Complex 1 is a percursor to a family of (N₃N)ZrX (N₃N, (N(CH₂CH₂NSIMe₃)³⁻) complexes which can be formed in good yields.
This reactivity is analogous to the expected reaction between HX with a (N₃N)ZrH ZrH complex. The scope of this reaction is general in that several functionalities can be reacted with 1 including phosphines, amines, thiols, alkynes, and phenol to afford new zirconium-elements bonds. These compounds were all characterized by various spectroscopic techniques where it was observed that the products were all pseudo-C₃v-symmetric. The reactivity of 1 can best be described as a hydride surrogate. Several compounds have been characterized by X-ray crystallography and the solid state supports the solution state spectroscopy.
Utilizing triamidoamine-supported zirconium phosphido complexes, a series of stoichiometric insertion reactions with small, polar molecules was performed. These small, polar molecules insert into the Zr-P bond in a 1,2 fashion to afford new phosphorus-element bonds. This observed reactivity suggested that phosphido complexes bearing the triamidoamine ligand might be catalysts for the hydrohydrophosphination of phosphination of unsaturated organic compounds. (N₃N)ZrPPh₂ was found an active catalysts in the hydrophosphination of phenyl acetylene, 1-hexyne and several carbodiimines to afford, anti-Markovnilov, vinyl phosphines and phosphosphaguanidate products respectively. The mechanism of this transformation was determined to occur via insertion of substrate into the Zr-P bond similar to several other hydrophosphination catalysts.
The insertion of isocyanides (R-N=C, R = Mes, Ph, Cy, tBu) into the Zr-P bond of primary phosphido complexes, (N₃N)ZrPHR' (R' = Ph, Cy)results in the formation of a 1,1-insertion product. This insertion product is meta-stable and thermally rearranges to afford phosphaalkene products of the form, l(N₃N)Zr[N(R)C=PR']. The synthesis of phosphaalkenes via insertion followed by bond-rearrangement appears to be general and several different isocyanides and phosphido complexes have been observed to react to give P=C products.
Liberation of the P=C moiety was found to occur by reactions with electrophiles. Depending upon the size of the electrophile, it was found that two products were possible. The first, when the electrophile is large, is a phosphine-substituted imine while the second, when the electrophile is small, is an amine-substituted phosphaalkene. This synthesis of of phosphaalkenes represents one of the cleanest, atom-economical routes towards P=C bonds known.
This reactivity is analogous to the expected reaction between HX with a (N₃N)ZrH ZrH complex. The scope of this reaction is general in that several functionalities can be reacted with 1 including phosphines, amines, thiols, alkynes, and phenol to afford new zirconium-elements bonds. These compounds were all characterized by various spectroscopic techniques where it was observed that the products were all pseudo-C₃v-symmetric. The reactivity of 1 can best be described as a hydride surrogate. Several compounds have been characterized by X-ray crystallography and the solid state supports the solution state spectroscopy.
Utilizing triamidoamine-supported zirconium phosphido complexes, a series of stoichiometric insertion reactions with small, polar molecules was performed. These small, polar molecules insert into the Zr-P bond in a 1,2 fashion to afford new phosphorus-element bonds. This observed reactivity suggested that phosphido complexes bearing the triamidoamine ligand might be catalysts for the hydrohydrophosphination of phosphination of unsaturated organic compounds. (N₃N)ZrPPh₂ was found an active catalysts in the hydrophosphination of phenyl acetylene, 1-hexyne and several carbodiimines to afford, anti-Markovnilov, vinyl phosphines and phosphosphaguanidate products respectively. The mechanism of this transformation was determined to occur via insertion of substrate into the Zr-P bond similar to several other hydrophosphination catalysts.
The insertion of isocyanides (R-N=C, R = Mes, Ph, Cy, tBu) into the Zr-P bond of primary phosphido complexes, (N₃N)ZrPHR' (R' = Ph, Cy)results in the formation of a 1,1-insertion product. This insertion product is meta-stable and thermally rearranges to afford phosphaalkene products of the form, l(N₃N)Zr[N(R)C=PR']. The synthesis of phosphaalkenes via insertion followed by bond-rearrangement appears to be general and several different isocyanides and phosphido complexes have been observed to react to give P=C products.
Liberation of the P=C moiety was found to occur by reactions with electrophiles. Depending upon the size of the electrophile, it was found that two products were possible. The first, when the electrophile is large, is a phosphine-substituted imine while the second, when the electrophile is small, is an amine-substituted phosphaalkene. This synthesis of of phosphaalkenes represents one of the cleanest, atom-economical routes towards P=C bonds known.