Photoelectron spectroscopy and bonding of iron and rhodium organometallic compounds with metal-carbon and metal-hydrogen bonds.

Persistent Link:
http://hdl.handle.net/10150/185692
Title:
Photoelectron spectroscopy and bonding of iron and rhodium organometallic compounds with metal-carbon and metal-hydrogen bonds.
Author:
Renshaw, Sharon Kintner
Issue Date:
1991
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
Gas phase ultraviolet photoelectron spectroscopy was used to investigate the electronic structure of organometallic compounds. Acetylide ligands in (η⁵-C₅H₅)Fe(CO)₂CECR (R = H, ᵗBu, Ph, C=CH) compounds are found to be effective π donor ligands. There is extensive interaction between the filled acetylide π and filled dπ orbitals. The HOMO and SHOMO of the acetylide compounds are partially localized on the acetylide β carbon. Variation of the R group causes both the σ and π donor ability of the acetylide to change significantly. The dπ/pπ mixing is more extensive in the R = ᵗBu or Ph compounds than in the R = H compound. In the compound CpFe(CO)₂(C=C-C=CH), the butadiyne π system mixes extensively with the metal dπ electrons. The d1t electron density is extended across the C₄H chain. These findings explain the observed reactivity toward electrophiles and Metal/acetylide communication. The first photoelectron spectra of Rh(III) compounds were obtained. The electronic structure of (η⁵-C₅Me₅)Rh(PMe₃)(Cl)(R) compounds, where R = CI, CH₃ or C₆H₅, is sensitive to changes in the R ligand. The a donor ability of the methyl and phenyl ligands are similar, but the phenyl has an additional filled/filled interaction with a metal dn orbital. The PES of (η⁵-C₅Me₅)Rh(PMe₃)(R)₂ (R = H or CH₃) revealed an electronic structure that is not isolobal with other d⁶ organometallic compounds. The HOMO and SHOMO are ligand based, as a result of the metal orbitals mixing with the Cp ring and M-R a bond combinations. The PES spectra of the compounds (η⁵-C₅H₄X)Rh(CO)₂ (X = NO₂, CF₃, CI, H, NMe₂, CH₃) gave measures of σ (inductive) and π (resonance) effects of the X substituent. The ionization energies of the metal based orbitals correlate with the carbonyl stretching frequencies and with Hammett σ(p) parameters. The X = Cl and NMe₂ compounds have significant π overlap with the Cp ring, and also have accelerated rates of associative CO substitution. The measures of inductive and resonance effects were correlated to the rates of CO substitution. The 7t terms are crucial to the correlation and suggest stabilization of an η³-Cp slipped ring intermediate. The PES of the associative substitution products (η⁵-C₅H₅)Rh(CO)L (L = PMe₃ or PPh3) have analogous electronic structure to CpRh(CO)₂, except that the valence ionizations are destabilized due to donor properties of the phosphines. The PPh₃ ligand is a better donor than PMe₃.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Dissertations, Academic; Chemistry, Inorganic; Chemistry, Physical and theoretical.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Chemistry; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Lichtenberger, Dennis L.

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titlePhotoelectron spectroscopy and bonding of iron and rhodium organometallic compounds with metal-carbon and metal-hydrogen bonds.en_US
dc.creatorRenshaw, Sharon Kintneren_US
dc.contributor.authorRenshaw, Sharon Kintneren_US
dc.date.issued1991en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractGas phase ultraviolet photoelectron spectroscopy was used to investigate the electronic structure of organometallic compounds. Acetylide ligands in (η⁵-C₅H₅)Fe(CO)₂CECR (R = H, ᵗBu, Ph, C=CH) compounds are found to be effective π donor ligands. There is extensive interaction between the filled acetylide π and filled dπ orbitals. The HOMO and SHOMO of the acetylide compounds are partially localized on the acetylide β carbon. Variation of the R group causes both the σ and π donor ability of the acetylide to change significantly. The dπ/pπ mixing is more extensive in the R = ᵗBu or Ph compounds than in the R = H compound. In the compound CpFe(CO)₂(C=C-C=CH), the butadiyne π system mixes extensively with the metal dπ electrons. The d1t electron density is extended across the C₄H chain. These findings explain the observed reactivity toward electrophiles and Metal/acetylide communication. The first photoelectron spectra of Rh(III) compounds were obtained. The electronic structure of (η⁵-C₅Me₅)Rh(PMe₃)(Cl)(R) compounds, where R = CI, CH₃ or C₆H₅, is sensitive to changes in the R ligand. The a donor ability of the methyl and phenyl ligands are similar, but the phenyl has an additional filled/filled interaction with a metal dn orbital. The PES of (η⁵-C₅Me₅)Rh(PMe₃)(R)₂ (R = H or CH₃) revealed an electronic structure that is not isolobal with other d⁶ organometallic compounds. The HOMO and SHOMO are ligand based, as a result of the metal orbitals mixing with the Cp ring and M-R a bond combinations. The PES spectra of the compounds (η⁵-C₅H₄X)Rh(CO)₂ (X = NO₂, CF₃, CI, H, NMe₂, CH₃) gave measures of σ (inductive) and π (resonance) effects of the X substituent. The ionization energies of the metal based orbitals correlate with the carbonyl stretching frequencies and with Hammett σ(p) parameters. The X = Cl and NMe₂ compounds have significant π overlap with the Cp ring, and also have accelerated rates of associative CO substitution. The measures of inductive and resonance effects were correlated to the rates of CO substitution. The 7t terms are crucial to the correlation and suggest stabilization of an η³-Cp slipped ring intermediate. The PES of the associative substitution products (η⁵-C₅H₅)Rh(CO)L (L = PMe₃ or PPh3) have analogous electronic structure to CpRh(CO)₂, except that the valence ionizations are destabilized due to donor properties of the phosphines. The PPh₃ ligand is a better donor than PMe₃.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectDissertations, Academicen_US
dc.subjectChemistry, Inorganicen_US
dc.subjectChemistry, Physical and theoretical.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineChemistryen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorLichtenberger, Dennis L.en_US
dc.contributor.committeememberMiller, Walter B.en_US
dc.contributor.committeememberEnemark, John H.en_US
dc.contributor.committeememberWigley, David E.en_US
dc.contributor.committeememberArmstrong, Neal R.en_US
dc.identifier.proquest9210299en_US
dc.identifier.oclc711905976en_US
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