Phenylselenenylalkanes, their adducts with the dirhodium complex Rh2(MTPA)4 and ligand exchange mechanisms in solution as studied by 1H, 13C and 77Se NMR spectroscopy
✍ Scribed by Shahid Malik; Stefan Moeller; Gábor Tóth; Tamás Gáti; Muhammad Iqbal Choudhary; Helmut Duddeck
- Publisher
- John Wiley and Sons
- Year
- 2003
- Tongue
- English
- Weight
- 192 KB
- Volume
- 41
- Category
- Article
- ISSN
- 0749-1581
- DOI
- 10.1002/mrc.1197
No coin nor oath required. For personal study only.
✦ Synopsis
Abstract
Twelve secondary phenylselenenylalkanes and ‐cycloalkanes were studied by ^1^H, ^13^C and ^77^Se NMR spectroscopy in the presence of the chiral dirhodium complex Rh~2~[(R)‐MTPA]~4~ [Rh–Rh; MTPA‐H = (R)‐(+)‐methoxytrifluoromethylphenylacetic acid, Mosher's acid]. The 1 : 1 and 2 : 1 adducts were identified in solution at low temperatures. Two different mechanisms of ligand exchange, ‘switch’ and ‘replacement,’ were characterized and their energy barriers estimated and steric congestion during the exchange transitions is discussed. Coordination‐induced shifts Δδ(^77^Se) are generally negative (shielding). For menthone bis(phenylselenoacetal) (7), these values indicate that a selection of the two selenium atoms occurs showing that 7 prefers complexation at the equatorial selenium atom whereas the axial selenium atom is hardly involved. Copyright © 2003 John Wiley & Sons, Ltd.