Photoelectron spectroscopy and rates of CO substitution of (η5-C5H4X)Rh(CO)2 compounds. Separation of σ and π Ring substituent effects

Dennis L Lichtenberger, Sharon K. Renshaw, Fred Basolo, Minsek Cheong

Research output: Contribution to journalArticle

23 Citations (Scopus)

Abstract

The He I photoelectron spectra for a series of monosubstituted (η5-C5H4X)Rh(CO)2 compounds are reported (where X = NO2, CF3, Cl, H, CH3, NMe2) and compared to the rates of carbonyl substitution reactions. The carbonyl substitution by phosphine follows an associative mechanism, and the rates are generally inhibited by greater electron richness at the metal center in these compounds. However, the rates for certain substitutions, particularly when X is Cl or NMe2, are faster than indicated by the inductive characteristics of these groups. The photoelectron spectra of the (η5-C5H4X)Rh(CO)2 compounds illustrate the effects of X on the electronic structure and rates of substitution. Pronounced shifts are seen in the cyclopentadienyl π and metal d valence ionizations as the X group is varied. The shifts of most of the valence ionizations closely follow the inductive capabilities of the X substituents, as also indicated by correlations with Hammett σ values and the carbonyl stretching frequencies of the compounds. Certain ionizations are also affected by orbitals of the X group that have π symmetry with respect to the cyclopentadienyl ring. Thus, the ionization energy shifts provide a relative measure of the inductive and resonance (π) interaction between X and the compound. The rates of CO substitution correlate with the ionizations when the shifts due to both the inductive and resonance (π) effects are taken into account. These results suggest that the "slipped ring" intermediate (η3-C5H4X)Rh(CO)2PPh3 is stabilized through π delocalization on the cyclopentadienyl ring, thus enhancing the rates of substitution.

Original languageEnglish (US)
Pages (from-to)148-156
Number of pages9
JournalOrganometallics
Volume10
Issue number1
StatePublished - 1991

Fingerprint

Carbon Monoxide
Photoelectron spectroscopy
Substitution reactions
photoelectron spectroscopy
substitutes
Ionization
rings
ionization
phosphine
shift
Photoelectrons
photoelectrons
Metals
valence
Ionization potential
phosphines
metals
Stretching
Electronic structure
electronic structure

ASJC Scopus subject areas

  • Inorganic Chemistry
  • Organic Chemistry

Cite this

Photoelectron spectroscopy and rates of CO substitution of (η5-C5H4X)Rh(CO)2 compounds. Separation of σ and π Ring substituent effects. / Lichtenberger, Dennis L; Renshaw, Sharon K.; Basolo, Fred; Cheong, Minsek.

In: Organometallics, Vol. 10, No. 1, 1991, p. 148-156.

Research output: Contribution to journalArticle

@article{d09326c79c9440bda744cc779f14b9d0,
title = "Photoelectron spectroscopy and rates of CO substitution of (η5-C5H4X)Rh(CO)2 compounds. Separation of σ and π Ring substituent effects",
abstract = "The He I photoelectron spectra for a series of monosubstituted (η5-C5H4X)Rh(CO)2 compounds are reported (where X = NO2, CF3, Cl, H, CH3, NMe2) and compared to the rates of carbonyl substitution reactions. The carbonyl substitution by phosphine follows an associative mechanism, and the rates are generally inhibited by greater electron richness at the metal center in these compounds. However, the rates for certain substitutions, particularly when X is Cl or NMe2, are faster than indicated by the inductive characteristics of these groups. The photoelectron spectra of the (η5-C5H4X)Rh(CO)2 compounds illustrate the effects of X on the electronic structure and rates of substitution. Pronounced shifts are seen in the cyclopentadienyl π and metal d valence ionizations as the X group is varied. The shifts of most of the valence ionizations closely follow the inductive capabilities of the X substituents, as also indicated by correlations with Hammett σ values and the carbonyl stretching frequencies of the compounds. Certain ionizations are also affected by orbitals of the X group that have π symmetry with respect to the cyclopentadienyl ring. Thus, the ionization energy shifts provide a relative measure of the inductive and resonance (π) interaction between X and the compound. The rates of CO substitution correlate with the ionizations when the shifts due to both the inductive and resonance (π) effects are taken into account. These results suggest that the {"}slipped ring{"} intermediate (η3-C5H4X)Rh(CO)2PPh3 is stabilized through π delocalization on the cyclopentadienyl ring, thus enhancing the rates of substitution.",
author = "Lichtenberger, {Dennis L} and Renshaw, {Sharon K.} and Fred Basolo and Minsek Cheong",
year = "1991",
language = "English (US)",
volume = "10",
pages = "148--156",
journal = "Organometallics",
issn = "0276-7333",
publisher = "American Chemical Society",
number = "1",

}

TY - JOUR

T1 - Photoelectron spectroscopy and rates of CO substitution of (η5-C5H4X)Rh(CO)2 compounds. Separation of σ and π Ring substituent effects

AU - Lichtenberger, Dennis L

AU - Renshaw, Sharon K.

AU - Basolo, Fred

AU - Cheong, Minsek

PY - 1991

Y1 - 1991

N2 - The He I photoelectron spectra for a series of monosubstituted (η5-C5H4X)Rh(CO)2 compounds are reported (where X = NO2, CF3, Cl, H, CH3, NMe2) and compared to the rates of carbonyl substitution reactions. The carbonyl substitution by phosphine follows an associative mechanism, and the rates are generally inhibited by greater electron richness at the metal center in these compounds. However, the rates for certain substitutions, particularly when X is Cl or NMe2, are faster than indicated by the inductive characteristics of these groups. The photoelectron spectra of the (η5-C5H4X)Rh(CO)2 compounds illustrate the effects of X on the electronic structure and rates of substitution. Pronounced shifts are seen in the cyclopentadienyl π and metal d valence ionizations as the X group is varied. The shifts of most of the valence ionizations closely follow the inductive capabilities of the X substituents, as also indicated by correlations with Hammett σ values and the carbonyl stretching frequencies of the compounds. Certain ionizations are also affected by orbitals of the X group that have π symmetry with respect to the cyclopentadienyl ring. Thus, the ionization energy shifts provide a relative measure of the inductive and resonance (π) interaction between X and the compound. The rates of CO substitution correlate with the ionizations when the shifts due to both the inductive and resonance (π) effects are taken into account. These results suggest that the "slipped ring" intermediate (η3-C5H4X)Rh(CO)2PPh3 is stabilized through π delocalization on the cyclopentadienyl ring, thus enhancing the rates of substitution.

AB - The He I photoelectron spectra for a series of monosubstituted (η5-C5H4X)Rh(CO)2 compounds are reported (where X = NO2, CF3, Cl, H, CH3, NMe2) and compared to the rates of carbonyl substitution reactions. The carbonyl substitution by phosphine follows an associative mechanism, and the rates are generally inhibited by greater electron richness at the metal center in these compounds. However, the rates for certain substitutions, particularly when X is Cl or NMe2, are faster than indicated by the inductive characteristics of these groups. The photoelectron spectra of the (η5-C5H4X)Rh(CO)2 compounds illustrate the effects of X on the electronic structure and rates of substitution. Pronounced shifts are seen in the cyclopentadienyl π and metal d valence ionizations as the X group is varied. The shifts of most of the valence ionizations closely follow the inductive capabilities of the X substituents, as also indicated by correlations with Hammett σ values and the carbonyl stretching frequencies of the compounds. Certain ionizations are also affected by orbitals of the X group that have π symmetry with respect to the cyclopentadienyl ring. Thus, the ionization energy shifts provide a relative measure of the inductive and resonance (π) interaction between X and the compound. The rates of CO substitution correlate with the ionizations when the shifts due to both the inductive and resonance (π) effects are taken into account. These results suggest that the "slipped ring" intermediate (η3-C5H4X)Rh(CO)2PPh3 is stabilized through π delocalization on the cyclopentadienyl ring, thus enhancing the rates of substitution.

UR - http://www.scopus.com/inward/record.url?scp=0000106437&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0000106437&partnerID=8YFLogxK

M3 - Article

AN - SCOPUS:0000106437

VL - 10

SP - 148

EP - 156

JO - Organometallics

JF - Organometallics

SN - 0276-7333

IS - 1

ER -