J. Junker et al., Structure determination of a key intermediate of the enantioselective Pd complex catalyzed allylic substitution reaction, CHEM-EUR J, 6(17), 2000, pp. 3281-3286
The structure of a catalytic intermediate with important implications for t
he interpretation of the stereochemical outcome of the palladium complex ca
talyzed allylic substitution with phosphino-oxazoline (PHOX) ligands is det
ermined by liquid state NMR. The complex displays a novel structure that is
highly distorted compared with other palladium eta(2)-olefin complexes kno
wn so far. The structure has been determined from nuclear overhauser data (
NOE), scalar coupling constants, and long range projection angle restraints
derived from dipole dipole cross-correlated relaxation of multiple quantum
coherence. The latter restraints have been implemented into a distance geo
metry protocol. The projection angle restraints yield a higher precision in
the determination of the relative orientation of the two molecular moietie
s and are essential to provide an exact structural definition of the olefin
ic part of the catalytic intermediate with respect to the ligand.