13C NMR chemical shielding tensor of the bridging methylene unit in cis-(μ-CH2)(μ-CO)[FeCp(CO)]2

Ae Ja Kim, Maria I Altbach, Leslie G. Butler

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

The principal elements of the 13C NMR chemical shielding tensor have been determined for the bridging methylene unit in cis-(μ-CH2)(μ-CO)[FeCp(CO)]2 from a combination of a Herzfeld-Berger analysis of the CP/MAS spectrum and a nonlinear least-squares fit of the proton-decoupled 13C powder pattern. The 13CH2 unit is both spatially isolated from other magnetic nuclei in the solid and largely motionally decoupled from dipolar interactions with the Cp ring protons. For the purpose of interpreting the proton-coupled 13C powder pattern, we have assumed that the carbon site of the dimetallocyclopropane unit lies on the intersection of two perpendicular mirror planes of symmetry. With this assumption, there are six possible relative orientations of the 13CH2 unit with respect to the principal axis system of the 13C chemical shielding tensor; simulations of the proton-coupled 13C powder patterns have been compared to the experimental spectrum, and the orientation of the chemical shielding tensor with respect to the molecular frameworks has been assigned. The C-H bond length and the H-C-H bond angle were obtained from the dipolar coupling tensor. A single, very large paramagnetic chemical shielding tensor element is a result of relatively weak carbon-metal bonds through two carbon atomic p orbitals and strong C-H bonds with the remaining carbon p orbital. Thus, these results are consistent with a molecular orbital analysis in which the methylene unit has σ-donating a1 and π-accepting b1 valence orbitals.

Original languageEnglish (US)
Pages (from-to)4831-4838
Number of pages8
JournalJournal of the American Chemical Society
Volume113
Issue number13
StatePublished - 1991
Externally publishedYes

Fingerprint

Carbon Monoxide
Shielding
Tensors
Protons
Carbon
Nuclear magnetic resonance
Powders
Chemical elements
Least-Squares Analysis
Bond length
Molecular orbitals
Metals
Mirrors
Carbon-13 Magnetic Resonance Spectroscopy

Keywords

  • Bridging methylene
  • Chemical shielding
  • Dipolar coupling
  • Nanoscopic MRI
  • Solid-state C NMR

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

13C NMR chemical shielding tensor of the bridging methylene unit in cis-(μ-CH2)(μ-CO)[FeCp(CO)]2. / Kim, Ae Ja; Altbach, Maria I; Butler, Leslie G.

In: Journal of the American Chemical Society, Vol. 113, No. 13, 1991, p. 4831-4838.

Research output: Contribution to journalArticle

@article{cfdae8c2f86f4078be450b7f74fc0f84,
title = "13C NMR chemical shielding tensor of the bridging methylene unit in cis-(μ-CH2)(μ-CO)[FeCp(CO)]2",
abstract = "The principal elements of the 13C NMR chemical shielding tensor have been determined for the bridging methylene unit in cis-(μ-CH2)(μ-CO)[FeCp(CO)]2 from a combination of a Herzfeld-Berger analysis of the CP/MAS spectrum and a nonlinear least-squares fit of the proton-decoupled 13C powder pattern. The 13CH2 unit is both spatially isolated from other magnetic nuclei in the solid and largely motionally decoupled from dipolar interactions with the Cp ring protons. For the purpose of interpreting the proton-coupled 13C powder pattern, we have assumed that the carbon site of the dimetallocyclopropane unit lies on the intersection of two perpendicular mirror planes of symmetry. With this assumption, there are six possible relative orientations of the 13CH2 unit with respect to the principal axis system of the 13C chemical shielding tensor; simulations of the proton-coupled 13C powder patterns have been compared to the experimental spectrum, and the orientation of the chemical shielding tensor with respect to the molecular frameworks has been assigned. The C-H bond length and the H-C-H bond angle were obtained from the dipolar coupling tensor. A single, very large paramagnetic chemical shielding tensor element is a result of relatively weak carbon-metal bonds through two carbon atomic p orbitals and strong C-H bonds with the remaining carbon p orbital. Thus, these results are consistent with a molecular orbital analysis in which the methylene unit has σ-donating a1 and π-accepting b1 valence orbitals.",
keywords = "Bridging methylene, Chemical shielding, Dipolar coupling, Nanoscopic MRI, Solid-state C NMR",
author = "Kim, {Ae Ja} and Altbach, {Maria I} and Butler, {Leslie G.}",
year = "1991",
language = "English (US)",
volume = "113",
pages = "4831--4838",
journal = "Journal of the American Chemical Society",
issn = "0002-7863",
publisher = "American Chemical Society",
number = "13",

}

TY - JOUR

T1 - 13C NMR chemical shielding tensor of the bridging methylene unit in cis-(μ-CH2)(μ-CO)[FeCp(CO)]2

AU - Kim, Ae Ja

AU - Altbach, Maria I

AU - Butler, Leslie G.

PY - 1991

Y1 - 1991

N2 - The principal elements of the 13C NMR chemical shielding tensor have been determined for the bridging methylene unit in cis-(μ-CH2)(μ-CO)[FeCp(CO)]2 from a combination of a Herzfeld-Berger analysis of the CP/MAS spectrum and a nonlinear least-squares fit of the proton-decoupled 13C powder pattern. The 13CH2 unit is both spatially isolated from other magnetic nuclei in the solid and largely motionally decoupled from dipolar interactions with the Cp ring protons. For the purpose of interpreting the proton-coupled 13C powder pattern, we have assumed that the carbon site of the dimetallocyclopropane unit lies on the intersection of two perpendicular mirror planes of symmetry. With this assumption, there are six possible relative orientations of the 13CH2 unit with respect to the principal axis system of the 13C chemical shielding tensor; simulations of the proton-coupled 13C powder patterns have been compared to the experimental spectrum, and the orientation of the chemical shielding tensor with respect to the molecular frameworks has been assigned. The C-H bond length and the H-C-H bond angle were obtained from the dipolar coupling tensor. A single, very large paramagnetic chemical shielding tensor element is a result of relatively weak carbon-metal bonds through two carbon atomic p orbitals and strong C-H bonds with the remaining carbon p orbital. Thus, these results are consistent with a molecular orbital analysis in which the methylene unit has σ-donating a1 and π-accepting b1 valence orbitals.

AB - The principal elements of the 13C NMR chemical shielding tensor have been determined for the bridging methylene unit in cis-(μ-CH2)(μ-CO)[FeCp(CO)]2 from a combination of a Herzfeld-Berger analysis of the CP/MAS spectrum and a nonlinear least-squares fit of the proton-decoupled 13C powder pattern. The 13CH2 unit is both spatially isolated from other magnetic nuclei in the solid and largely motionally decoupled from dipolar interactions with the Cp ring protons. For the purpose of interpreting the proton-coupled 13C powder pattern, we have assumed that the carbon site of the dimetallocyclopropane unit lies on the intersection of two perpendicular mirror planes of symmetry. With this assumption, there are six possible relative orientations of the 13CH2 unit with respect to the principal axis system of the 13C chemical shielding tensor; simulations of the proton-coupled 13C powder patterns have been compared to the experimental spectrum, and the orientation of the chemical shielding tensor with respect to the molecular frameworks has been assigned. The C-H bond length and the H-C-H bond angle were obtained from the dipolar coupling tensor. A single, very large paramagnetic chemical shielding tensor element is a result of relatively weak carbon-metal bonds through two carbon atomic p orbitals and strong C-H bonds with the remaining carbon p orbital. Thus, these results are consistent with a molecular orbital analysis in which the methylene unit has σ-donating a1 and π-accepting b1 valence orbitals.

KW - Bridging methylene

KW - Chemical shielding

KW - Dipolar coupling

KW - Nanoscopic MRI

KW - Solid-state C NMR

UR - http://www.scopus.com/inward/record.url?scp=2042498206&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=2042498206&partnerID=8YFLogxK

M3 - Article

AN - SCOPUS:2042498206

VL - 113

SP - 4831

EP - 4838

JO - Journal of the American Chemical Society

JF - Journal of the American Chemical Society

SN - 0002-7863

IS - 13

ER -