Irregular cyclization reactions in titanocenes bearing pendant double bonds
| Autor: | Lenka Lukešová, Róbert Gyepes, Petr Štěpnička, Michal Horáček, Jiří Kubišta, Karel Mach, Ivana Císařová |
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| Rok vydání: | 2004 |
| Předmět: |
Steric effects
chemistry.chemical_classification Double bond Magnesium Organic Chemistry chemistry.chemical_element Crystal structure Biochemistry Inorganic Chemistry Crystallography Paramagnetism chemistry X-ray crystallography Materials Chemistry Diamagnetism Physical and Theoretical Chemistry Titanium |
| Zdroj: | Journal of Organometallic Chemistry. 689:1919-1929 |
| ISSN: | 0022-328X |
| DOI: | 10.1016/j.jorganchem.2004.02.040 |
| Popis: | Reduction of methyl-substituted titanocene dichlorides bearing pendant double bonds [TiCl2{η5-C5Me4(CH2CMeCH2)}2] (1) and [TiCl2{η5-C5Me4(SiMe2(CH2)2CHCH2)}2] (2) with magnesium yielded diamagnetic Ti(IV) compound [Ti{η1:η1:η5-C5Me3(CH2)(CH2CH(Me)CH2)}{η5-C5Me4(CH2C(Me)CH2)}] (4) and paramagnetic Ti(III) compound [Ti{η5-C5Me4(SiMe2CH2CHCHMe)}(μ-η3,η1:η5,η1(Ti:Mg){C5Me3(CH2)(SiMe2CHCHCMe)})Mg(OC4H8)2] (6), respectively. The reluctance of titanocene intermediates to undergo intramolecular cyclization to cyclopentadienyl-ring-tethered titanacycles (as typically observed) can be explained by a shortness of the 2-methylallyl group and steric hindrance of its double bond in the former case and, in the latter case, by an attack of magnesium on the titanocene intermediate, faster than cyclization reactions. The crystal structures of 4 and 6 were determined by single-crystal X-ray diffraction. |
| Databáze: | OpenAIRE |
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