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On the Theme of Amidiniophosphines: Synthesis and Reactivity of Benzo-, Diimidazolo-Tris-Annelated P -Aminodiazaphosphepines.
- Source :
-
Phosphorus, Sulfur & Silicon & the Related Elements . 2015, Vol. 190 Issue 5/6, p789-802. 14p. - Publication Year :
- 2015
-
Abstract
- After a brief overview of the current development of carbeniophosphine ligands for applications in catalysis, in particular of imidazoliophosphines, a focus is given on the reference class of moderately flexible benzo-,diimidazolo-2,3,4,5,6,7-tris-annelated 3,6-diazaphosphepine derivatives with various exocyclic P–R substituents. The cases R = NMe2, NiPr2are addressed by comparison to the known cases R = Ph,tBu. After selective N,N′-dimethylation of the imidazole nitrogen atoms with MeOTf, further P-oxidation of the resulting dication withm-CPBA is shown to occur readily for R = NiPr2, as previously reported for R =tBu. In contrast, the same oxidative treatment of a parent neutral P-aminophosphepine is found to afford acis/transstereoisomeric mixture of the P-oxide. On the basis of line shape analyses of1H and31P NMR spectra between 313 and 373 K, the free enthalpy of activation of the stereo-conversion process is shown to be ca 17 kcal/mol. ROESY1H NMR experiments show that the major isomer exhibits acisorientation of the NiPr2group and the phenylene bridge. The corresponding boat conformation of the diazaphosphepine ring is confirmed by X-ray crystallography. As in the R =tBu series, the same boat conformation is observed in the crystal state of the dicationic oxide and neutral and dicationic P(III) parents. [ABSTRACT FROM PUBLISHER]
Details
- Language :
- English
- ISSN :
- 10426507
- Volume :
- 190
- Issue :
- 5/6
- Database :
- Academic Search Index
- Journal :
- Phosphorus, Sulfur & Silicon & the Related Elements
- Publication Type :
- Academic Journal
- Accession number :
- 103642872
- Full Text :
- https://doi.org/10.1080/10426507.2014.1002613