Pincer Complexes with Isopropyl Substituents A Density Functional Theory Study

Handle URI:
http://hdl.handle.net/10754/229291
Title:
Pincer Complexes with Isopropyl Substituents A Density Functional Theory Study
Authors:
Lim, XiaoZhi
Abstract:
Complexes with pincer ligand moieties have garnered much attention in the past few decades. They have been shown to be highly active catalysts in several known transition metal-catalyzed organic reactions as well as some unprecedented organic transformations. At the same time, the use of computational organometallic chemistry to aid in the understanding of the mechanisms in organometallic catalysis for the development of improved catalysts is on the rise. While it was common in earlier studies to reduce computational cost by truncating donor group substituents on complexes such as tertbutyl or isopropyl groups to hydrogen or methyl groups, recent advancements in the processing capabilities of computer clusters and codes have streamlined the time required for calculations. As the full modeling of complexes become increasingly popular, a commonly overlooked aspect, especially in the case of complexes bearing isopropyl substituents, is the conformational analysis of complexes. Isopropyl groups generate a different conformer with each 120 ° rotation (rotamer), and it has been found that each rotamer typically resides in its own potential energy well in density functional theory studies. As a result, it can be challenging to select the most appropriate structure for a theoretical study, as the adjustment of isopropyl substituents from a higher-energy rotamer to the lowest-energy rotamer usually does not occur during structure optimization. In this report, the influence of the arrangement of isopropyl substituents in pincer complexes on calculated complex structure energies as well as a case study on the mechanism of the isomerization of an iPrPCP-Fe complex is covered. It was found that as many as 324 rotamers can be generated for a single complex, as in the case of an iPrPCP-Ni formato complex, with the energy difference between the global minimum and the highest local minimum being as large as 16.5 kcalmol-1. In the isomerization of a iPrPCP-Fe complex, it was found that the isopropyl substituents not only influence the calculated structure energies, but they dictate the mechanism of isomerization with the rotation of isopropyl substituents from the arrangement in the starting material complex to the arrangement in the product complex being the rate-determining step.
Advisors:
Huang, Kuo-Wei ( 0000-0003-1900-2658 )
Committee Member:
Eppinger, Jörg ( 0000-0001-7886-7059 ) ; Lai, Zhiping ( 0000-0001-9555-6009 )
KAUST Department:
Physical Sciences and Engineering (PSE) Division
Program:
Chemical Sciences
Issue Date:
11-Dec-2011
Type:
Thesis
Appears in Collections:
Theses; Physical Sciences and Engineering (PSE) Division; Chemical Science Program

Full metadata record

DC FieldValue Language
dc.contributor.advisorHuang, Kuo-Weien
dc.contributor.authorLim, XiaoZhien
dc.date.accessioned2012-06-17T07:54:44Zen
dc.date.available2012-06-17T07:54:44Zen
dc.date.issued2011-12-11en
dc.identifier.urihttp://hdl.handle.net/10754/229291en
dc.description.abstractComplexes with pincer ligand moieties have garnered much attention in the past few decades. They have been shown to be highly active catalysts in several known transition metal-catalyzed organic reactions as well as some unprecedented organic transformations. At the same time, the use of computational organometallic chemistry to aid in the understanding of the mechanisms in organometallic catalysis for the development of improved catalysts is on the rise. While it was common in earlier studies to reduce computational cost by truncating donor group substituents on complexes such as tertbutyl or isopropyl groups to hydrogen or methyl groups, recent advancements in the processing capabilities of computer clusters and codes have streamlined the time required for calculations. As the full modeling of complexes become increasingly popular, a commonly overlooked aspect, especially in the case of complexes bearing isopropyl substituents, is the conformational analysis of complexes. Isopropyl groups generate a different conformer with each 120 ° rotation (rotamer), and it has been found that each rotamer typically resides in its own potential energy well in density functional theory studies. As a result, it can be challenging to select the most appropriate structure for a theoretical study, as the adjustment of isopropyl substituents from a higher-energy rotamer to the lowest-energy rotamer usually does not occur during structure optimization. In this report, the influence of the arrangement of isopropyl substituents in pincer complexes on calculated complex structure energies as well as a case study on the mechanism of the isomerization of an iPrPCP-Fe complex is covered. It was found that as many as 324 rotamers can be generated for a single complex, as in the case of an iPrPCP-Ni formato complex, with the energy difference between the global minimum and the highest local minimum being as large as 16.5 kcalmol-1. In the isomerization of a iPrPCP-Fe complex, it was found that the isopropyl substituents not only influence the calculated structure energies, but they dictate the mechanism of isomerization with the rotation of isopropyl substituents from the arrangement in the starting material complex to the arrangement in the product complex being the rate-determining step.en
dc.language.isoenen
dc.subjectPincer Complexesen
dc.subjectIsopropylen
dc.subjectIsomerizationen
dc.subjectconformational analysisen
dc.subjectDensity Functional Theoryen
dc.titlePincer Complexes with Isopropyl Substituents A Density Functional Theory Studyen
dc.typeThesisen
dc.contributor.departmentPhysical Sciences and Engineering (PSE) Divisionen
thesis.degree.grantorKing Abdullah University of Science and Technologyen_GB
dc.contributor.committeememberEppinger, Jörgen
dc.contributor.committeememberLai, Zhipingen
thesis.degree.disciplineChemical Sciencesen
thesis.degree.nameMaster of Scienceen
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