Ionization-structure relationships in metal-phosphine interactions.

Persistent Link:
http://hdl.handle.net/10150/184942
Title:
Ionization-structure relationships in metal-phosphine interactions.
Author:
Jatcko, Mark Edward
Issue Date:
1989
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:
The techniques of valence photoelectron spectroscopy (PES), X-ray diffraction, molecular orbital calculations, and multi-nuclear NMR are combined in a comparison of metal-phosphine bonding in a series of phosphine substituted molybdenum and tungsten metal carbonyl complexes, M(CO)(6-n)(P)(n) [n = 1,2,3,4,6]. The phosphine, P, represents either the mono-dentate phosphine, PMe₃, or one phosphine unit in the diphosphines, Me₂P(CH₂)ₓPMe₂, [x = 1, bis(dimethylphosphino)methane (DMPM); x = 2, 1,2-bis(dimethylphosphino)ethane (DMPE)]. Comparison of PMe₃ and the diphosphines in mono-dentate coordination (i.e. η¹-Mo(CO)₅DMPE) indicates the σ-donor strength is essentially identical for the three phosphines studied. Comparison of PMe₃ and the diphosphines in cis-chelating geometries reveals essentially identical charge at the coordinated phosphorus atoms and nearly identical charge at the metal center for cis-M(CO)₄(PMe₃)₂ and cis-M(CO)₄DMPE despite different local P-M-P bond angles. The X-ray crystal structures reveal a "twist" of the phosphine ligand when in sterically strained coordination geometries. The phosphine twist results in a "bent" metal-phosphine bond and is evaluated based on both electronic and steric considerations. The phosphine twist principle is used in studies on the nature of phosphine ligand electronic effects in the M(CO)(6-n)(P)(n) series at high substitution numbers, n. The PES data of the DMPE complexes for n = 4, cis-Mo(CO)₂(DMPE)₂, and n = 6, Mo(DMPE)₃, show symmetric metal electronic structure, but also a deviation from the previously observed additive behavior of phosphine electronic effects. The PES data for cis-Mo(CO)₂(PMe₃)₄ reveal a symmetric metal electronic structure due to sterically induced ligand-ligand interactions in this metal carbonyl complex. Multi-nuclear NMR data (³¹P and ⁹⁵Mo) are presented and the results discussed in light of the important ligand-ligand interactions observed in the PES studies. In addition, comparison of the NMR results for the mono-dentate and chelating phosphine complexes and the PES metal electronic structures provides a possible contribution to the ring chelate effect that is observed in the ³¹P and ⁹⁵Mo chemical shifts. The ring chelate effect refers to the unexplained relative differences between the ³¹P and ⁹⁵Mo chemical shifts of the cis-(PR₃)₂ complexes and the chelating diphosphine analogues.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Metal complexes; Phosphine; Photoelectron spectroscopy; Electronic structure
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Chemistry; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Litchenberger, Dennis L.

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleIonization-structure relationships in metal-phosphine interactions.en_US
dc.creatorJatcko, Mark Edwarden_US
dc.contributor.authorJatcko, Mark Edwarden_US
dc.date.issued1989en_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.abstractThe techniques of valence photoelectron spectroscopy (PES), X-ray diffraction, molecular orbital calculations, and multi-nuclear NMR are combined in a comparison of metal-phosphine bonding in a series of phosphine substituted molybdenum and tungsten metal carbonyl complexes, M(CO)(6-n)(P)(n) [n = 1,2,3,4,6]. The phosphine, P, represents either the mono-dentate phosphine, PMe₃, or one phosphine unit in the diphosphines, Me₂P(CH₂)ₓPMe₂, [x = 1, bis(dimethylphosphino)methane (DMPM); x = 2, 1,2-bis(dimethylphosphino)ethane (DMPE)]. Comparison of PMe₃ and the diphosphines in mono-dentate coordination (i.e. η¹-Mo(CO)₅DMPE) indicates the σ-donor strength is essentially identical for the three phosphines studied. Comparison of PMe₃ and the diphosphines in cis-chelating geometries reveals essentially identical charge at the coordinated phosphorus atoms and nearly identical charge at the metal center for cis-M(CO)₄(PMe₃)₂ and cis-M(CO)₄DMPE despite different local P-M-P bond angles. The X-ray crystal structures reveal a "twist" of the phosphine ligand when in sterically strained coordination geometries. The phosphine twist results in a "bent" metal-phosphine bond and is evaluated based on both electronic and steric considerations. The phosphine twist principle is used in studies on the nature of phosphine ligand electronic effects in the M(CO)(6-n)(P)(n) series at high substitution numbers, n. The PES data of the DMPE complexes for n = 4, cis-Mo(CO)₂(DMPE)₂, and n = 6, Mo(DMPE)₃, show symmetric metal electronic structure, but also a deviation from the previously observed additive behavior of phosphine electronic effects. The PES data for cis-Mo(CO)₂(PMe₃)₄ reveal a symmetric metal electronic structure due to sterically induced ligand-ligand interactions in this metal carbonyl complex. Multi-nuclear NMR data (³¹P and ⁹⁵Mo) are presented and the results discussed in light of the important ligand-ligand interactions observed in the PES studies. In addition, comparison of the NMR results for the mono-dentate and chelating phosphine complexes and the PES metal electronic structures provides a possible contribution to the ring chelate effect that is observed in the ³¹P and ⁹⁵Mo chemical shifts. The ring chelate effect refers to the unexplained relative differences between the ³¹P and ⁹⁵Mo chemical shifts of the cis-(PR₃)₂ complexes and the chelating diphosphine analogues.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectMetal complexesen_US
dc.subjectPhosphineen_US
dc.subjectPhotoelectron spectroscopyen_US
dc.subjectElectronic structureen_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.advisorLitchenberger, Dennis L.en_US
dc.contributor.committeememberEnemark, John H.en_US
dc.contributor.committeememberWigley, David E.en_US
dc.contributor.committeememberArmstrong, Neal R.en_US
dc.contributor.committeememberSalzman, W. R.en_US
dc.identifier.proquest9014671en_US
dc.identifier.oclc703616919en_US
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