Self-adaptable catalysts: substrate-dependent ligand configuration.
Pd(II) allyl and Pd(0) olefin complexes containing the configurationally labile ligand 1,2-bis-[4,5-dihydro-3H-dibenzo[c-e]azepino]ethane were studied as models for intermediates in Pd-catalyzed allylic alkylations. According to NMR and DFT studies, the ligand prefers C(s) conformation in both eta3-1,3-diphenylpropenyl and eta3-cyclohexenyl Pd(II) complexes, whereas in Pd(0) olefin complexes it adopts different conformations in complexes derived from the two types of allyl systems in both solution and, as verified by X-ray crystallography, in the solid state. These results demonstrate that the Pd complex is capable of adapting its structure to the reacting substrate. The different structural preferences also provide an explanation for the behavior of 1,3-diphenyl-2-propenyl acetate and 2-cyclohexenyl acetate in Pd-catalyzed allylic alkylations using pseudo-C2 and pseudo-C(s) symmetric ligands.
Zalubovskis
Raivis
R
KTH School of Chemical Science and Engineering, Department of Chemistry, Organic Chemistry, SE 100 44 Stockholm, Sweden.
Bouet
Alexis
A
Fjellander
Ester
E
Constant
Samuel
S
Linder
David
D
Fischer
Andreas
A
Lacour
Jérôme
J
Privalov
Timofei
T
Moberg
Christina
C