Pentacoordinated organoaluminum complexes: A computational insight

Handle URI:
http://hdl.handle.net/10754/562464
Title:
Pentacoordinated organoaluminum complexes: A computational insight
Authors:
Milione, Stefano; Milano, Giuseppe; Cavallo, Luigi ( 0000-0002-1398-338X )
Abstract:
The geometry and the electronic structure of a series of organometallic pentacoordinated aluminum complexes bearing tri- or tetradentate N,O-based ligands have been investigated with theoretical methods. The BP86, B3LYP, and M06 functionals reproduce with low accuracy the geometry of the selected complexes. The worst result was obtained for the complex bearing a Schiff base ligand with a pendant donor arm, aeimpAlMe2 (aeimp = N-2-(dimethylamino)ethyl-(3,5-di-tert-butyl)salicylaldimine). In particular, the Al-Namine bond distance was unacceptably overestimated. This failure suggests a reasonably flat potential energy surface with respect to Al-N elongation, indicating a weak interaction with probably a strong component of dispersion forces. MP2 and M06-2X methods led to an acceptable value for the same Al-N distance. Better results were obtained with the addition of the dispersion correction to the hybrid B3LYP functional (B3LYP-D). Natural bond orbital analysis revealed that the contribution of the d orbital to the bonding is very small, in agreement with several previous studies of hypervalent molecules. The donation of electronic charge from the ligand to metal mainly consists in the interactions of the lone pairs on the donor atoms of the ligands with the s and p valence orbitals of the aluminum. The covalent bonding of the Al with the coordinated ligand is weak, and the interactions between Al and the coordinated ligands are largely ionic. To further explore the geometrical and electronic factors affecting the formation of these pentacoordianted aluminum complexes, we considered the tetracoordinated complex impAlMe2 (imp = N-isopropyl-(3,5-di-tert-butyl)salicylaldimine)), analogous to aeimpAlMe 2, and we investigated the potential energy surface around the aluminum atom corresponding to the approach of NMe3 to the metal center. At the MP2/6-31G(d) level of theory, a weak attraction was revealed only when NMe3 heads toward the metal center through the directions trans to the nitrogen atom. The analysis of the binding energies for this adducts revealed that the formation of the pentacoordinated derivative is a result of a subtle balance between the penalty paid to deform the impAlMe2 complex and energy gain resulting from interaction between the two fragments. © 2012 American Chemical Society.
KAUST Department:
KAUST Catalysis Center (KCC); Physical Sciences and Engineering (PSE) Division; Chemical Science Program
Publisher:
American Chemical Society (ACS)
Journal:
Organometallics
Issue Date:
24-Dec-2012
DOI:
10.1021/om300689g
Type:
Article
ISSN:
02767333
Appears in Collections:
Articles; Physical Sciences and Engineering (PSE) Division; Chemical Science Program; KAUST Catalysis Center (KCC)

Full metadata record

DC FieldValue Language
dc.contributor.authorMilione, Stefanoen
dc.contributor.authorMilano, Giuseppeen
dc.contributor.authorCavallo, Luigien
dc.date.accessioned2015-08-03T10:39:09Zen
dc.date.available2015-08-03T10:39:09Zen
dc.date.issued2012-12-24en
dc.identifier.issn02767333en
dc.identifier.doi10.1021/om300689gen
dc.identifier.urihttp://hdl.handle.net/10754/562464en
dc.description.abstractThe geometry and the electronic structure of a series of organometallic pentacoordinated aluminum complexes bearing tri- or tetradentate N,O-based ligands have been investigated with theoretical methods. The BP86, B3LYP, and M06 functionals reproduce with low accuracy the geometry of the selected complexes. The worst result was obtained for the complex bearing a Schiff base ligand with a pendant donor arm, aeimpAlMe2 (aeimp = N-2-(dimethylamino)ethyl-(3,5-di-tert-butyl)salicylaldimine). In particular, the Al-Namine bond distance was unacceptably overestimated. This failure suggests a reasonably flat potential energy surface with respect to Al-N elongation, indicating a weak interaction with probably a strong component of dispersion forces. MP2 and M06-2X methods led to an acceptable value for the same Al-N distance. Better results were obtained with the addition of the dispersion correction to the hybrid B3LYP functional (B3LYP-D). Natural bond orbital analysis revealed that the contribution of the d orbital to the bonding is very small, in agreement with several previous studies of hypervalent molecules. The donation of electronic charge from the ligand to metal mainly consists in the interactions of the lone pairs on the donor atoms of the ligands with the s and p valence orbitals of the aluminum. The covalent bonding of the Al with the coordinated ligand is weak, and the interactions between Al and the coordinated ligands are largely ionic. To further explore the geometrical and electronic factors affecting the formation of these pentacoordianted aluminum complexes, we considered the tetracoordinated complex impAlMe2 (imp = N-isopropyl-(3,5-di-tert-butyl)salicylaldimine)), analogous to aeimpAlMe 2, and we investigated the potential energy surface around the aluminum atom corresponding to the approach of NMe3 to the metal center. At the MP2/6-31G(d) level of theory, a weak attraction was revealed only when NMe3 heads toward the metal center through the directions trans to the nitrogen atom. The analysis of the binding energies for this adducts revealed that the formation of the pentacoordinated derivative is a result of a subtle balance between the penalty paid to deform the impAlMe2 complex and energy gain resulting from interaction between the two fragments. © 2012 American Chemical Society.en
dc.publisherAmerican Chemical Society (ACS)en
dc.titlePentacoordinated organoaluminum complexes: A computational insighten
dc.typeArticleen
dc.contributor.departmentKAUST Catalysis Center (KCC)en
dc.contributor.departmentPhysical Sciences and Engineering (PSE) Divisionen
dc.contributor.departmentChemical Science Programen
dc.identifier.journalOrganometallicsen
dc.contributor.institutionDipartimento di Chimica e Biologia, Universitaè di Salerno, via Ponte don Melillo, I-84084 Fisciano (SA), Italyen
kaust.authorCavallo, Luigien
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