Geminal dehydrogenation of ether and amine C(sp3)H2 groups by electron-rich Ru(ii) and OsElectronic supplementary information (ESI) available: crystallographic data, fractional coordinates and isotropic thermal parameters, anisotropic thermal parameters, and bond distances and angles. See http://www.rsc.org/suppdata/nj/b2/b200168n
| Autor: | Joseph N. Coalter, Odile Eisenstein, Kenneth G. Caulton, Hélène Gérard, German Ferrando-Miguel, John C. Huffman |
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| Rok vydání: | 2002 |
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| Zdroj: | New Journal of Chemistry. 26:687-700 |
| ISSN: | 1369-9261 1144-0546 |
| Popis: | Reaction of [RuHCl(PiPr3)2]2 with THF or dioxolane doubly dehydrogenates the carbon α to the oxygen to yield RuHCl(H2)(PiPr3)2, together with the coordinated cyclic carbene, RuHCl[CO(CH2)2E](PiPr3)2, where E=CH2 or O. In the presence of CH2CHtBu as hydrogen acceptor, all Ru is converted to its carbene complex. The cyclic amines RN(CH2)4 (R=H, Me) react analogously, to produce N-substituted carbene complexes by geminal dehydrogenation; a crystal structure is presented for the carbene complex with R=H, which reveals intermolecular NH⋯Cl hydrogen bonding. Similar chemistry is established for Os(H)3Cl(PiPr3)2, at 25°C, in the presence of H2CCHtBu, to give OsHCl[CO(CH2)3](PiPr3)2. Pyrrolidine reacts rapidly at 25°C to give first a 1∶1 amine adduct, then slowly the trihydride carbene Os(H)3Cl[C(NH)(CH2)3](PiPr3)2, together with H2. Os(H)2Cl2(PiPr3)2 is first dehydrochlorinated by one mole of pyrrolidine, then a second mole of pyrrolidine is geminally dehydrogenated to form Os(H)3Cl[C(NH)(CH2)3](PiPr3)2. The five-coordinated carbene OsHCl[CO(CH2)3](PiPr3)2 will add H2, and the resulting product exists as two isomers, a trihydride with Cl cis to the carbene and a species with Cl trans to carbene and H and “2H” mutually trans. Isomer preferences, strength of H2 binding, and carbene plane orientation are discussed, together with DFT calculations on the thermodynamics of ether dehydrogenation by ruthenium. The latter reveal that coordination of removed H2 to Ru is essential to achieving favorable thermodynamics. |
| Databáze: | OpenAIRE |
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