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Phenylselenenylalkanes, their adducts with the dirhodium complex Rh 2 (MTPA) 4 and ligand exchange mechanisms in solution as studied by 1 H, 13 C and 77 Se NMR spectroscopy
Author(s) -
Malik Shahid,
Moeller Stefan,
Tóth Gábor,
Gáti Tamás,
Choudhary Muhammad Iqbal,
Duddeck Helmut
Publication year - 2003
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1197
Subject(s) - chemistry , steric effects , adduct , ligand (biochemistry) , selenium , rhodium , stereochemistry , nuclear magnetic resonance spectroscopy , atom (system on chip) , crystallography , catalysis , organic chemistry , biochemistry , receptor , computer science , embedded system
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.