How do the electronic structures of low-symmetry metal-hydride and -alkyl complexes compare? Photoelectron spectroscopy and computational studies of (η5-C5R5)Re(NO)(L)R′(L = CO, P(C6H5)3; R, R′ = H, CH3)

Dennis L Lichtenberger, Nadine E. Gruhn, Anjana Rai-Chaudhuri, Sharon K. Renshaw, John A. Gladysz, Haijun Jiao, Jeff Seyler, Alain Igau

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Abstract

The electronic structures of CpRe(NO)(L)R and Cp*Re(NO)(L)R (Cp = *5-C5H5, Cp* = η5-C5(CH3)5; L = CO, P(C6H5)3; R = H, CH3) are studied using gas-phase photoelectron spectroscopy and density functional theory. Separate valence ionizations from the three occupied metal-based orbitals of the d6 Re center, the Re-R σ bond orbitals, and the predominantly Cp e1″ pπ orbitals are clearly observed. Comparison of the shapes and energies of the Cp and σ(Re-R) ionizations indicates an additional direct interaction between these orbitals that is sensitive to energy matching. This interaction results in a more delocalized σ-bonding framework for the methyl complexes than for the analogous hydrides and halides. The energy shifts and cross-sections of the metal-based ionizations provide quantitative measures of the different abilities of the nitrosyl, carbonyl, and phosphine ligands to delocalize and stabilize the metal electron density through π back-bonding. In these molecules the stabilization of a metal-based ionization by an NO ligand (∼1.4 eV) is about twice that by a CO ligand (∼0.7 eV), which is in turn about twice that by a P(C6H5)3 ligand (∼0.4 eV). The shifts of the metal-based ionization energies when the hydride ligand is replaced by methyl show that the methyl ligand is acting as a weak π donor. The first metal-based ionization shifts more than the second upon substitution of methyl for hydride, because it is less delocalized and consequently has more metal character for π interaction with the R ligand. This difference in the two metal π orbital distributions, along with the differences in energy, influences the rotational orientation of ligands at this site. The extent of this π interaction is sensitive to the electron richness at the metal center.

Original languageEnglish (US)
Pages (from-to)5494-5504
Number of pages11
JournalOrganometallics
Volume21
Issue number25
DOIs
StatePublished - Dec 9 2002

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metal hydrides
Carbon Monoxide
Photoelectron spectroscopy
Hydrides
Electronic structure
Metals
photoelectron spectroscopy
electronic structure
Ligands
ligands
symmetry
Ionization
metals
ionization
orbitals
hydrides
phosphine
shift
energy
interactions

ASJC Scopus subject areas

  • Inorganic Chemistry
  • Organic Chemistry

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How do the electronic structures of low-symmetry metal-hydride and -alkyl complexes compare? Photoelectron spectroscopy and computational studies of (η5-C5R5)Re(NO)(L)R′(L = CO, P(C6H5)3; R, R′ = H, CH3). / Lichtenberger, Dennis L; Gruhn, Nadine E.; Rai-Chaudhuri, Anjana; Renshaw, Sharon K.; Gladysz, John A.; Jiao, Haijun; Seyler, Jeff; Igau, Alain.

In: Organometallics, Vol. 21, No. 25, 09.12.2002, p. 5494-5504.

Research output: Contribution to journalArticle

Lichtenberger, Dennis L ; Gruhn, Nadine E. ; Rai-Chaudhuri, Anjana ; Renshaw, Sharon K. ; Gladysz, John A. ; Jiao, Haijun ; Seyler, Jeff ; Igau, Alain. / How do the electronic structures of low-symmetry metal-hydride and -alkyl complexes compare? Photoelectron spectroscopy and computational studies of (η5-C5R5)Re(NO)(L)R′(L = CO, P(C6H5)3; R, R′ = H, CH3). In: Organometallics. 2002 ; Vol. 21, No. 25. pp. 5494-5504.
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abstract = "The electronic structures of CpRe(NO)(L)R and Cp*Re(NO)(L)R (Cp = *5-C5H5, Cp* = η5-C5(CH3)5; L = CO, P(C6H5)3; R = H, CH3) are studied using gas-phase photoelectron spectroscopy and density functional theory. Separate valence ionizations from the three occupied metal-based orbitals of the d6 Re center, the Re-R σ bond orbitals, and the predominantly Cp e1″ pπ orbitals are clearly observed. Comparison of the shapes and energies of the Cp and σ(Re-R) ionizations indicates an additional direct interaction between these orbitals that is sensitive to energy matching. This interaction results in a more delocalized σ-bonding framework for the methyl complexes than for the analogous hydrides and halides. The energy shifts and cross-sections of the metal-based ionizations provide quantitative measures of the different abilities of the nitrosyl, carbonyl, and phosphine ligands to delocalize and stabilize the metal electron density through π back-bonding. In these molecules the stabilization of a metal-based ionization by an NO ligand (∼1.4 eV) is about twice that by a CO ligand (∼0.7 eV), which is in turn about twice that by a P(C6H5)3 ligand (∼0.4 eV). The shifts of the metal-based ionization energies when the hydride ligand is replaced by methyl show that the methyl ligand is acting as a weak π donor. The first metal-based ionization shifts more than the second upon substitution of methyl for hydride, because it is less delocalized and consequently has more metal character for π interaction with the R ligand. This difference in the two metal π orbital distributions, along with the differences in energy, influences the rotational orientation of ligands at this site. The extent of this π interaction is sensitive to the electron richness at the metal center.",
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T1 - How do the electronic structures of low-symmetry metal-hydride and -alkyl complexes compare? Photoelectron spectroscopy and computational studies of (η5-C5R5)Re(NO)(L)R′(L = CO, P(C6H5)3; R, R′ = H, CH3)

AU - Lichtenberger, Dennis L

AU - Gruhn, Nadine E.

AU - Rai-Chaudhuri, Anjana

AU - Renshaw, Sharon K.

AU - Gladysz, John A.

AU - Jiao, Haijun

AU - Seyler, Jeff

AU - Igau, Alain

PY - 2002/12/9

Y1 - 2002/12/9

N2 - The electronic structures of CpRe(NO)(L)R and Cp*Re(NO)(L)R (Cp = *5-C5H5, Cp* = η5-C5(CH3)5; L = CO, P(C6H5)3; R = H, CH3) are studied using gas-phase photoelectron spectroscopy and density functional theory. Separate valence ionizations from the three occupied metal-based orbitals of the d6 Re center, the Re-R σ bond orbitals, and the predominantly Cp e1″ pπ orbitals are clearly observed. Comparison of the shapes and energies of the Cp and σ(Re-R) ionizations indicates an additional direct interaction between these orbitals that is sensitive to energy matching. This interaction results in a more delocalized σ-bonding framework for the methyl complexes than for the analogous hydrides and halides. The energy shifts and cross-sections of the metal-based ionizations provide quantitative measures of the different abilities of the nitrosyl, carbonyl, and phosphine ligands to delocalize and stabilize the metal electron density through π back-bonding. In these molecules the stabilization of a metal-based ionization by an NO ligand (∼1.4 eV) is about twice that by a CO ligand (∼0.7 eV), which is in turn about twice that by a P(C6H5)3 ligand (∼0.4 eV). The shifts of the metal-based ionization energies when the hydride ligand is replaced by methyl show that the methyl ligand is acting as a weak π donor. The first metal-based ionization shifts more than the second upon substitution of methyl for hydride, because it is less delocalized and consequently has more metal character for π interaction with the R ligand. This difference in the two metal π orbital distributions, along with the differences in energy, influences the rotational orientation of ligands at this site. The extent of this π interaction is sensitive to the electron richness at the metal center.

AB - The electronic structures of CpRe(NO)(L)R and Cp*Re(NO)(L)R (Cp = *5-C5H5, Cp* = η5-C5(CH3)5; L = CO, P(C6H5)3; R = H, CH3) are studied using gas-phase photoelectron spectroscopy and density functional theory. Separate valence ionizations from the three occupied metal-based orbitals of the d6 Re center, the Re-R σ bond orbitals, and the predominantly Cp e1″ pπ orbitals are clearly observed. Comparison of the shapes and energies of the Cp and σ(Re-R) ionizations indicates an additional direct interaction between these orbitals that is sensitive to energy matching. This interaction results in a more delocalized σ-bonding framework for the methyl complexes than for the analogous hydrides and halides. The energy shifts and cross-sections of the metal-based ionizations provide quantitative measures of the different abilities of the nitrosyl, carbonyl, and phosphine ligands to delocalize and stabilize the metal electron density through π back-bonding. In these molecules the stabilization of a metal-based ionization by an NO ligand (∼1.4 eV) is about twice that by a CO ligand (∼0.7 eV), which is in turn about twice that by a P(C6H5)3 ligand (∼0.4 eV). The shifts of the metal-based ionization energies when the hydride ligand is replaced by methyl show that the methyl ligand is acting as a weak π donor. The first metal-based ionization shifts more than the second upon substitution of methyl for hydride, because it is less delocalized and consequently has more metal character for π interaction with the R ligand. This difference in the two metal π orbital distributions, along with the differences in energy, influences the rotational orientation of ligands at this site. The extent of this π interaction is sensitive to the electron richness at the metal center.

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