Electronic structure and bonding in four-coordinate organometallic complexes of aluminum. Valence photoelectron spectra of BHT-H, Me3Al(PMe3), and Me2(BHT)Al(PMe3)

Dennis L Lichtenberger, Royston H. Hogan, Matthew D. Healy, Andrew R. Barron

Research output: Contribution to journalArticle

21 Citations (Scopus)

Abstract

The He I valence photoelectron spectra of the Lewis acid-base adducts Me3Al(PMe3) and Me2(BHT)Al(PMe3) (BHT-H = 2,6-di-tert-butyl-4-methylphenol) have been obtained to characterize the electronic structure and bonding in four-coordinate organometallic complexes of aluminum. To aid in the assignment of the spectrum of Me2(BHT)Al(PMe3), the spectrum of the free alcohol, BHT-H, was also obtained. The first and second ionizations of the free BHT-H alcohol show vibrational progressions associated with the symmetric C-C phenyl ring stretching modes, consistent with the b1 and a2 π ionizations, respectively, of monosubstituted phenyl rings. In the photoelectron spectrum of BHT coordinated to aluminum in Me2(BHT)Al(PMe3), the corresponding phenoxide a2 ionization retains the vibrational structure, but the individual vibrational components are lost in the ionization that corresponds most closely with the b1. The loss of vibrational fine structure associated with ionization from the phenyl π b1 orbital in the coordinated phenoxide shows that the phenoxide is involved in a π interaction with the Me2Al(PMe3) portion of the molecule. In addition, the aluminum center in Me2(BHT)Al(PM3) feels a more negative charge potential than the aluminum center in Me3Al(PMe3), as shown by the Al-P σ ionization occurring at lower binding energy in Me3Al(PMe3). This is counter to the σ inductive effects of an alkoxide compared to an alkyl and shows that the BHT is acting as a π electron donor. The change in band shape of the Al-P σ ionization between Me3Al(PMe3) and Me2(BHT)Al(PMe3) indicates that the oxygen p π orbital of the phenoxide ligand is interacting directly with the Al-P bonding orbital. The relationship between experimental ionization potentials and bond strengths of the Al-P σ bond in Me3Al (PMe3) and Me2(BHT)Al(PMe3), consistent with π donation from the phenoxide into the predominantly Al-P σ* orbital.

Original languageEnglish (US)
Pages (from-to)3369-3374
Number of pages6
JournalJournal of the American Chemical Society
Volume112
Issue number9
StatePublished - Apr 25 1990

Fingerprint

Butylated Hydroxytoluene
Organometallics
Photoelectrons
Aluminum
Ionization
Electronic structure
Alcohols
Ionization potential
Binding energy
Lewis Bases
Stretching
Lewis Acids
Ligands
Molecules
Oxygen
Acids
Electrons

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

Electronic structure and bonding in four-coordinate organometallic complexes of aluminum. Valence photoelectron spectra of BHT-H, Me3Al(PMe3), and Me2(BHT)Al(PMe3). / Lichtenberger, Dennis L; Hogan, Royston H.; Healy, Matthew D.; Barron, Andrew R.

In: Journal of the American Chemical Society, Vol. 112, No. 9, 25.04.1990, p. 3369-3374.

Research output: Contribution to journalArticle

@article{bec472b21dad4352ba232bd330d46ebf,
title = "Electronic structure and bonding in four-coordinate organometallic complexes of aluminum. Valence photoelectron spectra of BHT-H, Me3Al(PMe3), and Me2(BHT)Al(PMe3)",
abstract = "The He I valence photoelectron spectra of the Lewis acid-base adducts Me3Al(PMe3) and Me2(BHT)Al(PMe3) (BHT-H = 2,6-di-tert-butyl-4-methylphenol) have been obtained to characterize the electronic structure and bonding in four-coordinate organometallic complexes of aluminum. To aid in the assignment of the spectrum of Me2(BHT)Al(PMe3), the spectrum of the free alcohol, BHT-H, was also obtained. The first and second ionizations of the free BHT-H alcohol show vibrational progressions associated with the symmetric C-C phenyl ring stretching modes, consistent with the b1 and a2 π ionizations, respectively, of monosubstituted phenyl rings. In the photoelectron spectrum of BHT coordinated to aluminum in Me2(BHT)Al(PMe3), the corresponding phenoxide a2 ionization retains the vibrational structure, but the individual vibrational components are lost in the ionization that corresponds most closely with the b1. The loss of vibrational fine structure associated with ionization from the phenyl π b1 orbital in the coordinated phenoxide shows that the phenoxide is involved in a π interaction with the Me2Al(PMe3) portion of the molecule. In addition, the aluminum center in Me2(BHT)Al(PM3) feels a more negative charge potential than the aluminum center in Me3Al(PMe3), as shown by the Al-P σ ionization occurring at lower binding energy in Me3Al(PMe3). This is counter to the σ inductive effects of an alkoxide compared to an alkyl and shows that the BHT is acting as a π electron donor. The change in band shape of the Al-P σ ionization between Me3Al(PMe3) and Me2(BHT)Al(PMe3) indicates that the oxygen p π orbital of the phenoxide ligand is interacting directly with the Al-P bonding orbital. The relationship between experimental ionization potentials and bond strengths of the Al-P σ bond in Me3Al (PMe3) and Me2(BHT)Al(PMe3), consistent with π donation from the phenoxide into the predominantly Al-P σ* orbital.",
author = "Lichtenberger, {Dennis L} and Hogan, {Royston H.} and Healy, {Matthew D.} and Barron, {Andrew R.}",
year = "1990",
month = "4",
day = "25",
language = "English (US)",
volume = "112",
pages = "3369--3374",
journal = "Journal of the American Chemical Society",
issn = "0002-7863",
publisher = "American Chemical Society",
number = "9",

}

TY - JOUR

T1 - Electronic structure and bonding in four-coordinate organometallic complexes of aluminum. Valence photoelectron spectra of BHT-H, Me3Al(PMe3), and Me2(BHT)Al(PMe3)

AU - Lichtenberger, Dennis L

AU - Hogan, Royston H.

AU - Healy, Matthew D.

AU - Barron, Andrew R.

PY - 1990/4/25

Y1 - 1990/4/25

N2 - The He I valence photoelectron spectra of the Lewis acid-base adducts Me3Al(PMe3) and Me2(BHT)Al(PMe3) (BHT-H = 2,6-di-tert-butyl-4-methylphenol) have been obtained to characterize the electronic structure and bonding in four-coordinate organometallic complexes of aluminum. To aid in the assignment of the spectrum of Me2(BHT)Al(PMe3), the spectrum of the free alcohol, BHT-H, was also obtained. The first and second ionizations of the free BHT-H alcohol show vibrational progressions associated with the symmetric C-C phenyl ring stretching modes, consistent with the b1 and a2 π ionizations, respectively, of monosubstituted phenyl rings. In the photoelectron spectrum of BHT coordinated to aluminum in Me2(BHT)Al(PMe3), the corresponding phenoxide a2 ionization retains the vibrational structure, but the individual vibrational components are lost in the ionization that corresponds most closely with the b1. The loss of vibrational fine structure associated with ionization from the phenyl π b1 orbital in the coordinated phenoxide shows that the phenoxide is involved in a π interaction with the Me2Al(PMe3) portion of the molecule. In addition, the aluminum center in Me2(BHT)Al(PM3) feels a more negative charge potential than the aluminum center in Me3Al(PMe3), as shown by the Al-P σ ionization occurring at lower binding energy in Me3Al(PMe3). This is counter to the σ inductive effects of an alkoxide compared to an alkyl and shows that the BHT is acting as a π electron donor. The change in band shape of the Al-P σ ionization between Me3Al(PMe3) and Me2(BHT)Al(PMe3) indicates that the oxygen p π orbital of the phenoxide ligand is interacting directly with the Al-P bonding orbital. The relationship between experimental ionization potentials and bond strengths of the Al-P σ bond in Me3Al (PMe3) and Me2(BHT)Al(PMe3), consistent with π donation from the phenoxide into the predominantly Al-P σ* orbital.

AB - The He I valence photoelectron spectra of the Lewis acid-base adducts Me3Al(PMe3) and Me2(BHT)Al(PMe3) (BHT-H = 2,6-di-tert-butyl-4-methylphenol) have been obtained to characterize the electronic structure and bonding in four-coordinate organometallic complexes of aluminum. To aid in the assignment of the spectrum of Me2(BHT)Al(PMe3), the spectrum of the free alcohol, BHT-H, was also obtained. The first and second ionizations of the free BHT-H alcohol show vibrational progressions associated with the symmetric C-C phenyl ring stretching modes, consistent with the b1 and a2 π ionizations, respectively, of monosubstituted phenyl rings. In the photoelectron spectrum of BHT coordinated to aluminum in Me2(BHT)Al(PMe3), the corresponding phenoxide a2 ionization retains the vibrational structure, but the individual vibrational components are lost in the ionization that corresponds most closely with the b1. The loss of vibrational fine structure associated with ionization from the phenyl π b1 orbital in the coordinated phenoxide shows that the phenoxide is involved in a π interaction with the Me2Al(PMe3) portion of the molecule. In addition, the aluminum center in Me2(BHT)Al(PM3) feels a more negative charge potential than the aluminum center in Me3Al(PMe3), as shown by the Al-P σ ionization occurring at lower binding energy in Me3Al(PMe3). This is counter to the σ inductive effects of an alkoxide compared to an alkyl and shows that the BHT is acting as a π electron donor. The change in band shape of the Al-P σ ionization between Me3Al(PMe3) and Me2(BHT)Al(PMe3) indicates that the oxygen p π orbital of the phenoxide ligand is interacting directly with the Al-P bonding orbital. The relationship between experimental ionization potentials and bond strengths of the Al-P σ bond in Me3Al (PMe3) and Me2(BHT)Al(PMe3), consistent with π donation from the phenoxide into the predominantly Al-P σ* orbital.

UR - http://www.scopus.com/inward/record.url?scp=0025179134&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0025179134&partnerID=8YFLogxK

M3 - Article

AN - SCOPUS:0025179134

VL - 112

SP - 3369

EP - 3374

JO - Journal of the American Chemical Society

JF - Journal of the American Chemical Society

SN - 0002-7863

IS - 9

ER -