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FT-IR Spectroscopic Studies of Tin-Modified Rhenium Alumina-Silica Metathesis Catalyst

Zawadzki J., Skupiński W., Kirszensztejn P., Wachowski L., Jamróz M. H., Dobrowolski J. Cz.

Polish Journal of Chemistry

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2000

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Vol. 74, nr 12

1755-1767

EN

FT-IR spectra of the products obtained in each step of the tetramethyltin (TMT)/3-wt. % Re2O7/Al2O3-SiO2 and TMT/Al2O3-SiO2 systems preparation are presented and discussed. The obtained spectra show that TMT reacts with alumina-silica hydroxyl groups already at room temperature, yielding surface methyltin compounds; NH4ReO4 reacts with alumina–silica surface at temperatures up to 423 K, yielding rhenium surface species and ammonia, which is strongly bonded by acidic sites of the Brönsted kind. FT-IR spectrum of the system TMT/3-wt.%Re2O7/Al2O3-SiO2 indicated the absence of surface methyl tin compounds observed on the surface system TMT/Al2O3-SiO2, and the presence of physically adsorbed TMT; after 5 h of evacuation of the TMT/3-wt. % Re2O7- /Al2O3-SiO2 system, the FT-IR spectrum indicated the presence of only a single band at 2977 cm–1, which may be assigned to the C–H bond stretching of the methyl group in the surface bridged (O, O) Re(=O)2CH3 complexes formed. Analysis of FT-IR results suggests formation of a new phase containing rhenium and aluminium ions, on which olefin sites active in olefin metathesis are formed in the system studied.

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FT-IR Spectroscopic Studies of Tin-Modified Rhenium Alumina-Silica Metathesis Catalyst

Zawadzki J., Skupiński W., Kirszensztejn P., Wachowski L., Jamróz M. H., Dobrowolski J. Cz.

Polish Journal of Chemistry

|

2000

|

Vol. 74, nr 12

1755-1767

EN

FT-IR spectra of the products obtained in each step of the tetramethyltin (TMT)/3-wt. % Re2O7/Al2O3-SiO2 and TMT/Al2O3-SiO2 systems preparation are presented and discussed. The obtained spectra show that TMT reacts with alumina-silica hydroxyl groups already at room temperature, yielding surface methyltin compounds; NH4ReO4 reacts with alumina–silica surface at temperatures up to 423 K, yielding rhenium surface species and ammonia, which is strongly bonded by acidic sites of the Brönsted kind. FT-IR spectrum of the system TMT/3-wt.%Re2O7/Al2O3-SiO2 indicated the absence of surface methyl tin compounds observed on the surface system TMT/Al2O3-SiO2, and the presence of physically adsorbed TMT; after 5 h of evacuation of the TMT/3-wt. % Re2O7- /Al2O3-SiO2 system, the FT-IR spectrum indicated the presence of only a single band at 2977 cm–1, which may be assigned to the C–H bond stretching of the methyl group in the surface bridged (O, O) Re(=O)2CH3 complexes formed. Analysis of FT-IR results suggests formation of a new phase containing rhenium and aluminium ions, on which olefin sites active in olefin metathesis are formed in the system studied.

3

The M(O2)X(YH3)3 dioxygen complexes (M=Rh, Co; X=F, Cl, Br, I; Y=N, P): an ab initio, DFT and semiempirical PM3(tm) study

Dobrowolski J. Cz., Jamróz M. H., Kazimirski J. K., Bajdor K., Borowiak M. A., Manna L., Miglietta M. L., Aresta M.

Polish Journal of Chemistry

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1998

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Vol. 72, nr 10

2205-2217

EN

The molecular structure, energetics and vibrations have been calculated for the MO2 moiety in the M(O2)X(YH3)3 series of metal dioxygen complexes at three levels of theory: ab initio (RHF/3-21G), DFT (B3PW91/3-21G) and semiempirical PM3(tm). The methods yielded the O-O distances consistent with the experimental values and similarly predicted the tendencies of geometrical parameters to change. The variation of the enthalpy of formation with the central metal atom, halogen and ligand seems to be in qualitative interconsistency, whereas changes in the MO2 moiety frequencies, found at different levels, disagree substantially.