Characterization of Silica-Supported Osmium Carbonyl Clusters by Magic-Angle-Spinning Carbon-13 NMR Spectroscopy

Thomas H. Walter; Greg R. Frauenhoff; John R. Shapley; Eric Oldfield

doi:10.1021/ic00025a011

Characterization of Silica-Supported Osmium Carbonyl Clusters by Magic-Angle-Spinning Carbon-13 NMR Spectroscopy

Thomas H. Walter, Greg R. Frauenhoff, John R. Shapley, Eric Oldfield

Chemistry

Research output: Contribution to journal › Article › peer-review

Abstract

We report the carbon-13 magic-angle-spinning nuclear magnetic resonance (NMR) spectra of silica-supported Os₃(¹³CO)₁₂ samples prepared in several different ways. Our results yield both the isotropic chemical shift and the principal components of the chemical shift tensor for each carbonyl resonance. Spectra have been assigned by comparison to solution NMR spectra of a variety of osmium carbonyl clusters that are models for the proposed surface-attached structures: HOs₃(CO)₁₀(OR) (R = CH₃, C₆H₅, SiEt₃), HOs₃(CO)₁₀(O₂CH), Os₃(CO)₁₀(OCH₃)₂, and [Os(CO)₃Cl₂]₂. Spectra of samples prepared by impregnation of silica with a solution of Os₃(¹³CO)₁₂ provide evidence for a physisorbed Os₃(CO)₁₂ species undergoing fast isotropic motion. For samples prepared by refluxing Os₃(¹³CO)₁₂ and SiO₂ in n-octane, a spectrum containing five distinct resonances is observed, consistent with a HOs₃(CO)₁₀(OSi=) species having C_s symmetry. The chemical shift anisotropy parameters measured for these resonances at 20 °C suggest that this species is undergoing rapid (≫32 kHz) large-angle (90-120°) rotational jumps. Spectra of samples prepared by vacuum pyrolysis (200 °C) are consistent with Os(II) carbonyl species that are immobile on the 10⁻⁵-10⁻⁴-s time scale. These results demonstrate the utility of ¹³C NMR spectroscopy for studying the structures and dynamics of supported metal carbonyl clusters.

Original language	English (US)
Pages (from-to)	4732-4739
Number of pages	8
Journal	Inorganic Chemistry
Volume	30
Issue number	25
DOIs	https://doi.org/10.1021/ic00025a011
State	Published - Dec 1 1991

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Physical and Theoretical Chemistry
Inorganic Chemistry

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10.1021/ic00025a011

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title = "Characterization of Silica-Supported Osmium Carbonyl Clusters by Magic-Angle-Spinning Carbon-13 NMR Spectroscopy",

abstract = "We report the carbon-13 magic-angle-spinning nuclear magnetic resonance (NMR) spectra of silica-supported Os3(13CO)12 samples prepared in several different ways. Our results yield both the isotropic chemical shift and the principal components of the chemical shift tensor for each carbonyl resonance. Spectra have been assigned by comparison to solution NMR spectra of a variety of osmium carbonyl clusters that are models for the proposed surface-attached structures: HOs3(CO)10(OR) (R = CH3, C6H5, SiEt3), HOs3(CO)10(O2CH), Os3(CO)10(OCH3)2, and [Os(CO)3Cl2]2. Spectra of samples prepared by impregnation of silica with a solution of Os3(13CO)12 provide evidence for a physisorbed Os3(CO)12 species undergoing fast isotropic motion. For samples prepared by refluxing Os3(13CO)12 and SiO2 in n-octane, a spectrum containing five distinct resonances is observed, consistent with a HOs3(CO)10(OSi=) species having Cs symmetry. The chemical shift anisotropy parameters measured for these resonances at 20 °C suggest that this species is undergoing rapid (≫32 kHz) large-angle (90-120°) rotational jumps. Spectra of samples prepared by vacuum pyrolysis (200 °C) are consistent with Os(II) carbonyl species that are immobile on the 10−5-10−4-s time scale. These results demonstrate the utility of 13C NMR spectroscopy for studying the structures and dynamics of supported metal carbonyl clusters.",

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AU - Walter, Thomas H.

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PY - 1991/12/1

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N2 - We report the carbon-13 magic-angle-spinning nuclear magnetic resonance (NMR) spectra of silica-supported Os3(13CO)12 samples prepared in several different ways. Our results yield both the isotropic chemical shift and the principal components of the chemical shift tensor for each carbonyl resonance. Spectra have been assigned by comparison to solution NMR spectra of a variety of osmium carbonyl clusters that are models for the proposed surface-attached structures: HOs3(CO)10(OR) (R = CH3, C6H5, SiEt3), HOs3(CO)10(O2CH), Os3(CO)10(OCH3)2, and [Os(CO)3Cl2]2. Spectra of samples prepared by impregnation of silica with a solution of Os3(13CO)12 provide evidence for a physisorbed Os3(CO)12 species undergoing fast isotropic motion. For samples prepared by refluxing Os3(13CO)12 and SiO2 in n-octane, a spectrum containing five distinct resonances is observed, consistent with a HOs3(CO)10(OSi=) species having Cs symmetry. The chemical shift anisotropy parameters measured for these resonances at 20 °C suggest that this species is undergoing rapid (≫32 kHz) large-angle (90-120°) rotational jumps. Spectra of samples prepared by vacuum pyrolysis (200 °C) are consistent with Os(II) carbonyl species that are immobile on the 10−5-10−4-s time scale. These results demonstrate the utility of 13C NMR spectroscopy for studying the structures and dynamics of supported metal carbonyl clusters.

AB - We report the carbon-13 magic-angle-spinning nuclear magnetic resonance (NMR) spectra of silica-supported Os3(13CO)12 samples prepared in several different ways. Our results yield both the isotropic chemical shift and the principal components of the chemical shift tensor for each carbonyl resonance. Spectra have been assigned by comparison to solution NMR spectra of a variety of osmium carbonyl clusters that are models for the proposed surface-attached structures: HOs3(CO)10(OR) (R = CH3, C6H5, SiEt3), HOs3(CO)10(O2CH), Os3(CO)10(OCH3)2, and [Os(CO)3Cl2]2. Spectra of samples prepared by impregnation of silica with a solution of Os3(13CO)12 provide evidence for a physisorbed Os3(CO)12 species undergoing fast isotropic motion. For samples prepared by refluxing Os3(13CO)12 and SiO2 in n-octane, a spectrum containing five distinct resonances is observed, consistent with a HOs3(CO)10(OSi=) species having Cs symmetry. The chemical shift anisotropy parameters measured for these resonances at 20 °C suggest that this species is undergoing rapid (≫32 kHz) large-angle (90-120°) rotational jumps. Spectra of samples prepared by vacuum pyrolysis (200 °C) are consistent with Os(II) carbonyl species that are immobile on the 10−5-10−4-s time scale. These results demonstrate the utility of 13C NMR spectroscopy for studying the structures and dynamics of supported metal carbonyl clusters.

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Characterization of Silica-Supported Osmium Carbonyl Clusters by Magic-Angle-Spinning Carbon-13 NMR Spectroscopy

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