Steric Effects in Reactions of Decamethyltitanocene Hydride with Internal Alkynes, Conjugated Diynes, and Conjugated Dienes
作者： Jiří Pinkas , Róbert Gyepes , Ivana Císařová , Jiří Kubišta , Michal Horáček
DOI: 10.1021/OM500296H
关键词: Substituent 、 Carbon-13 NMR 、 Stereochemistry 、 Agostic interaction 、 Trimethylsilyl 、 Chemistry 、 Medicinal chemistry 、 Electron paramagnetic resonance 、 Conjugated system 、 Hydride 、 Steric effects
摘要: Titanocene hydride [Cp*2TiH] (Cp* = η5-C5Me5) (1) readily inserts simple internal alkynes R1C≡CR2 into its Ti–H bond, yielding titanocene alkenyl Ti(III) compounds of two structural types. The less sterically congested products [Cp*2Ti(R1C═CHR2)] (2a–e) contain a σ1-bonded group, whereas the bearing at least one trimethylsilyl substituent and other bulky substituents (R1 SiMe3; R2 SiMe3, 4a; CMe3, 4b; Ph, 4c) possess remarkable agostic bond group. This feature is consistent with solution EPR spectra 4a–4c showing doublet due to coupling hydrogen nucleus d1 electron. Compound 1 reacts molar equivalent conjugated buta-1,3-diynes (RC≡C)2 give η3-butenyne complexes (R 5a; 5b). 2a–2e 5a 5b were oxidatively chlorinated PbCl2 Ti(IV) chloro-alkenyl [Cp*2TiCl(R1C═CHR2)] 3a–3e chloro-alkenynes 6a 6b, respectively. 1H 13C NMR 3...
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