Trianionic Pincer Complexes of Niobium and Tantalum as Precatalysts for ROMP of Norbornene
| Autor: | Khalil A. Abboud, Sudarsan VenkatRamani, Adam S. Veige, Christopher D. Roland, James G. Zhang, Ion Ghiviriga |
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| Rok vydání: | 2016 |
| Předmět: |
Steric effects
010405 organic chemistry Ligand Organic Chemistry Nuclear magnetic resonance spectroscopy ROMP 010402 general chemistry Metathesis 01 natural sciences 0104 chemical sciences Pincer movement Inorganic Chemistry chemistry.chemical_compound chemistry Polymerization Polymer chemistry Organic chemistry Physical and Theoretical Chemistry Norbornene |
| Zdroj: | Organometallics. 35:2675-2682 |
| ISSN: | 1520-6041 0276-7333 |
| DOI: | 10.1021/acs.organomet.6b00421 |
| Popis: | This report details the synthesis and characterization of a series of Nb complexes and one tantalum complex supported by the [CF3–ONO]3– trianionic pincer-type ligand. Access to the trianionic Nb dichloride complex, [CF3–ONO]NbCl2(OEt2) (3-Et2O), allows for the synthesis of Nb-dialkyl complexes, [CF3–ONO]NbR2 (where R = benzyl (5), neopentylsilyl (6), neophyl (7)). The sterically encumbered Nb-neophyl complex (7) is thermally stable and fails to convert to the alkylidene even in the presence of donor ligands. Complex 7, however, promotes catalytic ring-opening metathesis polymerization (ROMP) of norbornene, suggesting the plausible intermediacy of a Nb-alkylidene. The corresponding Ta analogue, [CF3–ONO]Ta(CH2C(CH3)2(C6H5))2 (9), requires dramatically higher temperatures to initiate ROMP and provides poor yields of polymer. Complexes 5 and 6 also promote ROMP of norbornene. Characterization of all new complexes includes multinuclear NMR spectroscopy and combustion analysis. For complex 7, characterization... |
| Databáze: | OpenAIRE |
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