[Ru(NHC)(xantphos)(CO)H2] complexes: intramolecular C–H activation and applications in C–C bond formation
- 27 May 2009
- journal article
- Published by Royal Society of Chemistry (RSC) in Dalton Transactions
- No. 35,p. 6941-6947
- https://doi.org/10.1039/b906010c
Abstract
Treatment of [Ru(PPh3)(xantphos)(CO)H2] (1) with the N-heterocyclic carbenes (NHCs) IEt2Me2 (1,3-diethyl-4,5-dimethylimidazol-2-ylidene), IiPr2Me2 (1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) and IMes (1,3-dimesitylimidazol-2-ylidene) at elevated temperature affords the C–H activated carbene complexes [Ru(NHC)′(xantphos)(CO)H] (2–4). In contrast, ICy (1,3-dicyclohexylimidazol-2-ylidene) reacts with 1 to give the substitution product [Ru(ICy)(xantphos)(CO)H2] (6), which can be converted into the C–H activated species [Ru(ICy)′(xantphos)(CO)H] (7) upon thermolysis in the presence of H2CCHSiMe3. Addition of H2 to 2 yields [Ru(IEt2Me2)(xantphos)(CO)H2] (5), while H2 reacts with 7 to reform 6. Complexes 2–4 and 7 catalyse the Knoevenagel reaction of PhCH2OH with tBuC(O)CH2CN, although they prove to be somewhat less active than the phosphine complex 1.Keywords
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