Carbodiimide metathesis catalyzed by vanadium oxo and imido complexes via imido transfer
| Autor: | K.R. Birdwhistell, J. Lanza, J. Pasos |
|---|---|
| Rok vydání: | 1999 |
| Předmět: |
Organic Chemistry
Xylene Vanadium chemistry.chemical_element Metathesis Biochemistry Medicinal chemistry Catalysis Inorganic Chemistry chemistry.chemical_compound chemistry Catalytic cycle Materials Chemistry Organic chemistry Physical and Theoretical Chemistry Efficient catalyst Isopropyl Carbodiimide |
| Zdroj: | Journal of Organometallic Chemistry. 584:200-205 |
| ISSN: | 0022-328X |
| DOI: | 10.1016/s0022-328x(99)00142-4 |
| Popis: | Vanadium oxo and imido complexes: V(NC 6 H 4 Me)(O t Bu) 3 ( 1 ), V(NC 6 H 4 Me)Cl 3 ( 2 ), V(O)(O t Bu) 3 ( 3 ), V(O)(O i Pr) 3 ( 4 ), V(O)(acac) 2 ( 5 ), are catalysts for the metathesis of symmetrical carbodiimides (RNCNR, where R=cyclohexyl, isopropyl, and p -tolyl). At 138°C in p -xylene using 5 mol% of complexes 1 – 5 , the above carbodiimides are metathesized to the asymmetrical carbodiimides: N -cyclohexyl, N ′- p -tolylcarbodiimide ( 6 ), N -isopropyl, N ′- p -tolylcarbodiimide ( 7 ), N -cyclohexyl, N ′-isopropylcarbodiimide ( 8 ). An equilibrium mixture of carbodiimides is reached within minutes to hours depending on the catalyst employed. Yields obtained from gas chromatography range from 32 to 70%. Complex 2 is the most efficient catalyst with a turnover frequency greater than 100 h −1 . The oxo complexes ( 3 – 5 ) appear to be precatalysts. A mechanism is proposed for initiation with oxo complexes and a subsequent catalytic cycle involving imido complexes. |
| Databáze: | OpenAIRE |
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