A Combined Theoretical-Experimental Study of the Inclusion of Niobocene Dichloride in Native and Permethylated -Cyclo
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- 作者：Clá ; udia C. L. Pereira ; Mariela Nolasco ; Susana S. Braga ; Filipe A. Almeida Paz ; Paulo Ribeiro-Claro ; Martyn Pillinger ; Isabel S. Gonç ; alves
- 刊名：Organometallics
- 出版年：2007
- 出版时间：August 13, 2007
- 年：2007
- 卷：26
- 期：17
- 页码：4220 - 4228
- 全文大小：377K
- 年卷期：v.26,no.17(August 13, 2007)
- ISSN：1520-6041
文摘
Inclusion complexes comprising niobocene dichloride, Cp2NbCl2, and either native 
-cyclodextrin (-CD) or permethylated -CD (TRIMEB) were prepared with a host:guest molar ratio of 1:1. The adductswere characterized in the solid state by powder X-ray diffraction (XRD), thermogravimetric analysis(TGA), 13C{1H} CP/MAS NMR, FTIR, and FT Raman spectroscopies. Ab initio calculations wereperformed in order to elucidate the possible inclusion geometries and calculate vibrational frequenciesfor Cp2NbCl2 in the region 100-1800 cm-1. The vibrational spectra indicated that neither the hosts northe guest were chemically modified upon inclusion complexation. Small wavenumber shifts in C-H,C-C, and metal-ligand vibrational modes were attributed to the effect of the host-guest interaction.Powder XRD showed that the -CD adduct was of low crystallinity, while the TRIMEB adduct wasquite crystalline. The powder XRD pattern of the TRIMEB adduct could be satisfactorily indexed in themonoclinic system with the space group P21. A hypothetical structural model for the crystal packing wasobtained through Monte Carlo optimizations using a reported TRIMEB geometry comprising a distortedelliptical cavity. An unrestrained Rietveld refinement of the structural model could not be carried outdue to the relatively low quality of the experimental powder XRD pattern. However, the plausibility ofthe host-guest interaction geometry, involving inclusion of one of the guest Cp ligands inside the CDcavity, was fully supported by the ab initio calculations.
-cyclodextrin (-CD) or permethylated -CD (TRIMEB) were prepared with a host:guest molar ratio of 1:1. The adductswere characterized in the solid state by powder X-ray diffraction (XRD), thermogravimetric analysis(TGA), 13C{1H} CP/MAS NMR, FTIR, and FT Raman spectroscopies. Ab initio calculations wereperformed in order to elucidate the possible inclusion geometries and calculate vibrational frequenciesfor Cp2NbCl2 in the region 100-1800 cm-1. The vibrational spectra indicated that neither the hosts northe guest were chemically modified upon inclusion complexation. Small wavenumber shifts in C-H,C-C, and metal-ligand vibrational modes were attributed to the effect of the host-guest interaction.Powder XRD showed that the -CD adduct was of low crystallinity, while the TRIMEB adduct wasquite crystalline. The powder XRD pattern of the TRIMEB adduct could be satisfactorily indexed in themonoclinic system with the space group P21. A hypothetical structural model for the crystal packing wasobtained through Monte Carlo optimizations using a reported TRIMEB geometry comprising a distortedelliptical cavity. An unrestrained Rietveld refinement of the structural model could not be carried outdue to the relatively low quality of the experimental powder XRD pattern. However, the plausibility ofthe host-guest interaction geometry, involving inclusion of one of the guest Cp ligands inside the CDcavity, was fully supported by the ab initio calculations.