C−H activation and C−C coupling reactions in 2-vinylpyridine cationic complexes of iridium
| Autor: | Isabel T. Dobrinovitch, Eduardo Sola, Marta Martín, Luis A. Oro, Janeth Navarro, Fernando J. Lahoz |
|---|---|
| Přispěvatelé: | Ministerio de Ciencia y Tecnología (España), Diputación General de Aragón, Universidad del Zulia |
| Jazyk: | angličtina |
| Rok vydání: | 2004 |
| Předmět: |
chemistry.chemical_classification
2-Vinylpyridine Stereochemistry Hydride Organic Chemistry Cationic polymerization Regioselectivity chemistry.chemical_element Medicinal chemistry law.invention Inorganic Chemistry chemistry.chemical_compound C c coupling chemistry law Iridium Physical and Theoretical Chemistry Crystallization Alkyl |
| Zdroj: | Digital.CSIC. Repositorio Institucional del CSIC instname |
| Popis: | The complex [IrH2(NCCH3)3(PiPr3)]BF4 (1) reacts with 2-vinylpyridine to form the hydride [IrH{NC5H4-2-Z-(CHCH)-κ-N,C}(NCCH3)2(PiPr3)]BF4 (3) in a reaction that likely involves the observed dihydride [IrH2(NC5H4-2-CHCH2-κ-N)(NCCH3)2(PiPr3)]BF4 (2). Crystallization of the C−H activation product 3 affords the dicationic derivative [IrH{μ-η2-NC5H4-2-(Z-CHCH)-κ-N,C}(NCCH3)(PiPr3)]2(BF4)2 (4). 3 reacts with 2-vinypyridine, CH2CH2, CH⋮CH, PhC⋮CH, tBuC⋮CH, and PhC⋮CPh to form the corresponding alkyl or alkenyl insertion products. The structure of [Ir(NC5H4-2-(Z-CHCH)-κ-N,C)(NC5H4-2-CH2CH2-κ-N,C)(NCCH3)(PiPr3)]BF4 (5), which contains two chelating ligands derived from 2-vinylpyridine, has been determined by X-ray diffraction. The other insertion products 7−11 retain the structure of the precursor 3 even after insertions of different regioselectivity, as evidenced by the 1-alkyne derivatives [Ir{C(Ph)CH2}{NC5H4-2-Z-(CHCH)-κ-N,C}(NCCH3)2(PiPr3)]BF4 (9) and [Ir(E-CHCHtBu){NC5H4-2-Z-(CHCH)-κ-N,C}(NCCH3)2(PiPr3)]BF4 (10). All obtained insertion products are stable toward the reductive elimination of C−C bonds. However, derivatives 9 and 10 undergo a C−C coupling reaction to form [Ir{NC5H4-2-Z-(CHCH)-κ-N,C}{NC5H4-2-Z-(CHCH)CH(R)CH2-κ-N,C}(NCCH3)(PiPr3)]BF4 (R = Ph, 12; R = tBu, 13) after treatment with 2-vinylpyridine excess. These latter products are isostructural, despite the different stereochemistry of the alkenyl ligands in the precursors. Under similar conditions, both the alkyl complex [Ir(Et){NC5H4-2-Z-(CHCH)-κ-N,C}(NCCH3)2(PiPr3)] BF4 (7) and the diphenylacetylene derivative [Ir{Z-C(Ph)CHPh}{NC5H4-2-Z-(CHCH)-κ-N,C}(NCCH3)2(PiPr3)]BF4 (11) form the compound [Ir{NC5H4-2-Z-(CHCH)-κ-N,C}2(NCCH3)(PiPr3)]BF4 (15), after elimination of ethane and cis-stilbene, respectively. These latter observations are discussed to conclude that the observed C−C coupling processes comprise the initial generation of an alkene at the coordination sphere of iridium followed by the alkene insertion into an Ir−C bond. Financial support for this research was provided by Plan Nacional de Investigación, MCYT (Project No. BQU2000-1170). J.N. thanks the Universidad del Zulia for a grant. I.T.D. thanks DGA for a grant. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|