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EnglishThe reaction of [CoIII(4,4′dmsalen)(CH2Cl)(S)], where 4,4′dmsalen = 4,4′-dimethylsalen and S = solvent, with pyridine led to the formation of [CoIII(4,4′dmsalen)(CH2py)(Cl)], containing a nonstabilized pyridinium ylide as axial ligand. The complex has been unambiguously characterized by single-crystal X-ray diffraction analysis. Time-resolved 1H NMR spectra showed that the formation of [CoIII(4,4′dmsalen)(CH2py)(Cl)] occurs in a two-step process involving a metallacyclized intermediate, cis-β-[CoIII(4,4′dmsalenCH2)(py)(S)]+. A similar experiment carried out in the presence of different nitrogen bases having higher pKa values (4-Me-py or 4-t-Bu-py) allowed a better separation of the two consecutive reactions. The almost complete conversion of [CoIII(4,4′dmsalen)(CH2Cl)(S)] in the cyclized intermediate before the formation of the ylide indicates that the ylide complex forms exclusively through the nucleophilic attack of the nitrogen base at the −CH2O– carbon of the cyclized species, whereas a parallel direct conversion through the displacement of Cl– from the axial CH2Cl group of [CoIII(4,4′dmsalen)(CH2Cl)(S)] may be ruled out.
| Titolo: | Formation and Structure of a Cobalt(III) Complex Containing a Nonstabilized Pyridinium Ylide Ligand |
| Autori: | |
| Data di pubblicazione: | 2014 |
| Rivista: | |
| Abstract: | The reaction of [CoIII(4,4′dmsalen)(CH2Cl)(S)], where 4,4′dmsalen = 4,4′-dimethylsalen and S = solvent, with pyridine led to the formation of [CoIII(4,4′dmsalen)(CH2py)(Cl)], containing a nonstabilized pyridinium ylide as axial ligand. The complex has been unambiguously characterized by single-crystal X-ray diffraction analysis. Time-resolved 1H NMR spectra showed that the formation of [CoIII(4,4′dmsalen)(CH2py)(Cl)] occurs in a two-step process involving a metallacyclized intermediate, cis-β-[CoIII(4,4′dmsalenCH2)(py)(S)]+. A similar experiment carried out in the presence of different nitrogen bases having higher pKa values (4-Me-py or 4-t-Bu-py) allowed a better separation of the two consecutive reactions. The almost complete conversion of [CoIII(4,4′dmsalen)(CH2Cl)(S)] in the cyclized intermediate before the formation of the ylide indicates that the ylide complex forms exclusively through the nucleophilic attack of the nitrogen base at the −CH2O– carbon of the cyclized species, whereas a parallel direct conversion through the displacement of Cl– from the axial CH2Cl group of [CoIII(4,4′dmsalen)(CH2Cl)(S)] may be ruled out. |
| Handle: | http://hdl.handle.net/11368/2829726 |
| Digital Object Identifier (DOI): | http://dx.doi.org/10.1021/om5007374 |
| Appare nelle tipologie: | 1.1 Articolo in Rivista |
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