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Niobium phosphine macrocyclic complexes Bowdridge, Michael R.
Abstract
The chemistry of the macrocycle PhP(CH₂SiMe₂NSiMe₂CH₂)₂PPh (abbreviated as [P₂N₂] within this thesis) with niobium(III) is explored. The paramagnetic chloride compound NbCl[P₂N₂] (1) is used as a starting material for other derivatives, such as {[P₂N₂]Nb}₂ (µ-N₂) (2) , Nb(CH₂SiMe₃)[P₂N₂] (6), and Nb(CH₂Ph)[P₂N₂ ] (9). Compound 1 forms adducts with small molecules and solvents, including CO which causes the complex to become diamagnetic. NbCl[P₂N₂] (1) reacts with KC₈ under 1 atm of N₂ to give {[P₂N₂]Nb}₂(µ-N₂) (2). Complex 2, characterized by X-ray crystallography, is found to have an end-on bound dinitrogen ligand with an N-N bond length of 1.272 (5) A . This is only the fourth niobium dinitrogen species to be structurally characterized. Reaction of 2 with 2 equivalents of Me₃N-HCl gives the original chloride 1 and 0.31 equivalents of hydrazine. Nb(CH₂SiMe₃)[P₂N₂] (6) and Nb(CH₂Ph)[P₂N₂] (9) are synthesized by reaction of chloride 1 with LiCH₂SiMe₃ and KCH₂Ph respectively. Reaction of trimethylsilylmethyl 6 with H₂ in benzene results in the formation of a cyclohexadienyl ligand complex, Nb(ƞ⁵-C₆H₇)[P₂N₂] (8). Also, reaction of compound 6 with CO results in the CO insertion and rearrangement with the trimethylsilylmethyl ligand to give an enolate complex. Compound 9 is determined to have an ƞ⁵ bound benzyl ligand. Preliminary investigations in the reaction of compound 1 with LiN(SiMe₃)₂, Mel, and KC₈ while under Ar give Nb{N(SiMe₃)₂}[P₂N₂] (4), Nb(MeI)Cl[P₂N₂] (10), and {[P₂N₂]Nb}₂ (3) respectively. Molecular structure information is given for {[P₂N₂]Nb}₂(µ-N₂)(µ-Cl) (5); the first characterized side-on bridged dinitrogen niobium complex. Studies into the elemental determinations of {[P₂N₂]Nb(µ-N₂) (2) and Nb(CH₂Ph)[P₂N₂] (9) reveal limitations in microanalysis due to the formation of stable niobium nitrides and carbides. ¹H NMR spectroscopy is successfully used for identification of all paramagnetic complexes within this thesis.
Item Metadata
Title |
Niobium phosphine macrocyclic complexes
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Creator | |
Publisher |
University of British Columbia
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Date Issued |
1998
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Description |
The chemistry of the macrocycle PhP(CH₂SiMe₂NSiMe₂CH₂)₂PPh (abbreviated as
[P₂N₂] within this thesis) with niobium(III) is explored. The paramagnetic chloride compound
NbCl[P₂N₂] (1) is used as a starting material for other derivatives, such as {[P₂N₂]Nb}₂ (µ-N₂)
(2) , Nb(CH₂SiMe₃)[P₂N₂] (6), and Nb(CH₂Ph)[P₂N₂ ] (9). Compound 1 forms adducts with
small molecules and solvents, including CO which causes the complex to become diamagnetic.
NbCl[P₂N₂] (1) reacts with KC₈ under 1 atm of N₂ to give {[P₂N₂]Nb}₂(µ-N₂) (2).
Complex 2, characterized by X-ray crystallography, is found to have an end-on bound dinitrogen
ligand with an N-N bond length of 1.272 (5) A . This is only the fourth niobium dinitrogen
species to be structurally characterized. Reaction of 2 with 2 equivalents of Me₃N-HCl gives the
original chloride 1 and 0.31 equivalents of hydrazine.
Nb(CH₂SiMe₃)[P₂N₂] (6) and Nb(CH₂Ph)[P₂N₂] (9) are synthesized by reaction of
chloride 1 with LiCH₂SiMe₃ and KCH₂Ph respectively. Reaction of trimethylsilylmethyl 6 with
H₂ in benzene results in the formation of a cyclohexadienyl ligand complex, Nb(ƞ⁵-C₆H₇)[P₂N₂]
(8). Also, reaction of compound 6 with CO results in the CO insertion and rearrangement with
the trimethylsilylmethyl ligand to give an enolate complex. Compound 9 is determined to have
an ƞ⁵ bound benzyl ligand.
Preliminary investigations in the reaction of compound 1 with LiN(SiMe₃)₂, Mel, and
KC₈ while under Ar give Nb{N(SiMe₃)₂}[P₂N₂] (4), Nb(MeI)Cl[P₂N₂] (10), and {[P₂N₂]Nb}₂
(3) respectively. Molecular structure information is given for {[P₂N₂]Nb}₂(µ-N₂)(µ-Cl) (5); the
first characterized side-on bridged dinitrogen niobium complex. Studies into the elemental
determinations of {[P₂N₂]Nb(µ-N₂) (2) and Nb(CH₂Ph)[P₂N₂] (9) reveal limitations in
microanalysis due to the formation of stable niobium nitrides and carbides. ¹H NMR
spectroscopy is successfully used for identification of all paramagnetic complexes within this
thesis.
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4532318 bytes
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Type | |
File Format |
application/pdf
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Language |
eng
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Date Available |
2009-05-20
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Provider |
Vancouver : University of British Columbia Library
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Rights |
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
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DOI |
10.14288/1.0061546
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Graduation Date |
1998-11
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Campus | |
Scholarly Level |
Graduate
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Aggregated Source Repository |
DSpace
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For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.