Supported organoactinides. High-resolution solid-state 13C NMR studies of catalytically active, alumina-bound (pentamethylcyclopentadienyl)thorium methyl and hydride complexes

Paul J. Toscano, Tobin J Marks

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Abstract

This contribution reports a high-resolution solid-state 13C NMR study of the organoactinides Cp′2Th(CH3)2, Cp′2Th(13CH3)2, and [Cp′2Th(μ-H)H]2 (Cp′ = η5-(CH3)5C5) adsorbed on partially dehydroxylated (PDA) or dehydroxylated (DA) γ-alumina. Cross-polarization (CP) combined with magic angle spinning (MAS) and high-power 1H decoupling produces adsorbate 13C NMR spectra of sufficient resolution and sensitivity to obtain significant structural information. On the basis of the observed 13C chemical shifts, line widths, and field dependence thereof as well as comparison to a number of model systems and dipolar dephasing experiments, methyl transfer from Th to Al on the surface of the support is proposed for the reaction of Cp′2Th(13CH3)2 with DA. Several types of experiments (Bloch decay, cessation of dipole decoupling, variable contact time) suggest that the adsorbed species are not highly mobile. On the other hand, adsorption of Cp′2Th(13CH3)2 on PDA results in protonolysis of the Th-CH3 units and the formation of surface Th-O-Al aluminoxy species. Useful correlations with the companion surface and catalysis study are presented. The utility of 13C CPMAS NMR spectroscopy in probing surface-bound metal alkyls (especially in proximity to quadrupolar support nuclei) is emphasized.

Original languageEnglish
Pages (from-to)653-659
Number of pages7
JournalJournal of the American Chemical Society
Volume107
Issue number3
Publication statusPublished - 1985

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Thorium
Aluminum Oxide
Hydrides
Alumina
Nuclear magnetic resonance
Catalysis
Adsorption
Magic angle spinning
Chemical shift
Magnetic Resonance Spectroscopy
Adsorbates
Metals
Linewidth
Nuclear magnetic resonance spectroscopy
Experiments
Polarization
Carbon-13 Magnetic Resonance Spectroscopy

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

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title = "Supported organoactinides. High-resolution solid-state 13C NMR studies of catalytically active, alumina-bound (pentamethylcyclopentadienyl)thorium methyl and hydride complexes",
abstract = "This contribution reports a high-resolution solid-state 13C NMR study of the organoactinides Cp′2Th(CH3)2, Cp′2Th(13CH3)2, and [Cp′2Th(μ-H)H]2 (Cp′ = η5-(CH3)5C5) adsorbed on partially dehydroxylated (PDA) or dehydroxylated (DA) γ-alumina. Cross-polarization (CP) combined with magic angle spinning (MAS) and high-power 1H decoupling produces adsorbate 13C NMR spectra of sufficient resolution and sensitivity to obtain significant structural information. On the basis of the observed 13C chemical shifts, line widths, and field dependence thereof as well as comparison to a number of model systems and dipolar dephasing experiments, methyl transfer from Th to Al on the surface of the support is proposed for the reaction of Cp′2Th(13CH3)2 with DA. Several types of experiments (Bloch decay, cessation of dipole decoupling, variable contact time) suggest that the adsorbed species are not highly mobile. On the other hand, adsorption of Cp′2Th(13CH3)2 on PDA results in protonolysis of the Th-CH3 units and the formation of surface Th-O-Al aluminoxy species. Useful correlations with the companion surface and catalysis study are presented. The utility of 13C CPMAS NMR spectroscopy in probing surface-bound metal alkyls (especially in proximity to quadrupolar support nuclei) is emphasized.",
author = "Toscano, {Paul J.} and Marks, {Tobin J}",
year = "1985",
language = "English",
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journal = "Journal of the American Chemical Society",
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T1 - Supported organoactinides. High-resolution solid-state 13C NMR studies of catalytically active, alumina-bound (pentamethylcyclopentadienyl)thorium methyl and hydride complexes

AU - Toscano, Paul J.

AU - Marks, Tobin J

PY - 1985

Y1 - 1985

N2 - This contribution reports a high-resolution solid-state 13C NMR study of the organoactinides Cp′2Th(CH3)2, Cp′2Th(13CH3)2, and [Cp′2Th(μ-H)H]2 (Cp′ = η5-(CH3)5C5) adsorbed on partially dehydroxylated (PDA) or dehydroxylated (DA) γ-alumina. Cross-polarization (CP) combined with magic angle spinning (MAS) and high-power 1H decoupling produces adsorbate 13C NMR spectra of sufficient resolution and sensitivity to obtain significant structural information. On the basis of the observed 13C chemical shifts, line widths, and field dependence thereof as well as comparison to a number of model systems and dipolar dephasing experiments, methyl transfer from Th to Al on the surface of the support is proposed for the reaction of Cp′2Th(13CH3)2 with DA. Several types of experiments (Bloch decay, cessation of dipole decoupling, variable contact time) suggest that the adsorbed species are not highly mobile. On the other hand, adsorption of Cp′2Th(13CH3)2 on PDA results in protonolysis of the Th-CH3 units and the formation of surface Th-O-Al aluminoxy species. Useful correlations with the companion surface and catalysis study are presented. The utility of 13C CPMAS NMR spectroscopy in probing surface-bound metal alkyls (especially in proximity to quadrupolar support nuclei) is emphasized.

AB - This contribution reports a high-resolution solid-state 13C NMR study of the organoactinides Cp′2Th(CH3)2, Cp′2Th(13CH3)2, and [Cp′2Th(μ-H)H]2 (Cp′ = η5-(CH3)5C5) adsorbed on partially dehydroxylated (PDA) or dehydroxylated (DA) γ-alumina. Cross-polarization (CP) combined with magic angle spinning (MAS) and high-power 1H decoupling produces adsorbate 13C NMR spectra of sufficient resolution and sensitivity to obtain significant structural information. On the basis of the observed 13C chemical shifts, line widths, and field dependence thereof as well as comparison to a number of model systems and dipolar dephasing experiments, methyl transfer from Th to Al on the surface of the support is proposed for the reaction of Cp′2Th(13CH3)2 with DA. Several types of experiments (Bloch decay, cessation of dipole decoupling, variable contact time) suggest that the adsorbed species are not highly mobile. On the other hand, adsorption of Cp′2Th(13CH3)2 on PDA results in protonolysis of the Th-CH3 units and the formation of surface Th-O-Al aluminoxy species. Useful correlations with the companion surface and catalysis study are presented. The utility of 13C CPMAS NMR spectroscopy in probing surface-bound metal alkyls (especially in proximity to quadrupolar support nuclei) is emphasized.

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