Metal Cation−Methyl Interactions in CB11Me12- Salts of Me3Ge+, Me3Sn+, and Me3Pb+
| Autor: | David M. Grant, Anita M. Orendt, Dewey H. Barich, Josef Michl, Ilya Zharov, Tsu Chien Weng, James E. Penner-Hahn, Zdenek Havlas |
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| Rok vydání: | 2004 |
| Předmět: |
Boron Compounds
Models Molecular Magnetic Resonance Spectroscopy Stereochemistry Static Electricity Crystal structure Biochemistry Catalysis Ion Colloid and Surface Chemistry Cations Alkane chemistry.chemical_classification Fourier Analysis Trimethyltin Compounds Germanium Chemistry Spectrum Analysis Charge density General Chemistry Nuclear magnetic resonance spectroscopy Crystallography Covalent bond Tetraethyl Lead Carborane Density functional theory |
| Zdroj: | Journal of the American Chemical Society. 126:12033-12046 |
| ISSN: | 1520-5126 0002-7863 |
| DOI: | 10.1021/ja0475205 |
| Popis: | Oxidation of Me(6)M(2) (M = Ge, Sn) and Me(4)Pb with the CB(11)Me(12)(*) radical in alkane solvents produced the insoluble salts Me(3)M(+)CB(11)Me(12)(-), characterized by CP-MAS NMR and EXAFS. The cations interact with methyl groups of CB(11)Me(12)(-) with coordination strength increasing from Pb to Ge. Density functional theory (DFT) calculations for the isolated ion pairs, Me(3)M(+)CB(11)Me(12)(-) (M = Ge, Sn), revealed three isomers with the cation above methyl 2, 7, or 12, and not above a BB edge or a BBB triangle. The interaction has a considerable covalent component, with the cation attempting to perform a backside S(E)2 substitution on the methyl carbon. In a fourth less favorable isomer the cation is near methyl 1, inclined toward methyl 2, and interacts with hydrogens. DFT atomic charge distributions and plots of the electrostatic potential on the surface of spheres centered at the CB(11)H(12)(-) and CB(11)Me(12)(-) icosahedra display the effects of uneven charge distribution within the anion and contradict the common belief that the negative charge of the cage anion is concentrated primarily on the cage boron atoms 7-12; in CB(11)Me(12)(-), roughly half is on the cage carbon and the rest on methyls 7-12. |
| Databáze: | OpenAIRE |
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