Premium
Diastereopure Cationic NCN‐Pincer Palladium Complexes with Square Planar η 4 ‐ N , C , N , O Coordination
Author(s) -
Gosiewska Silvia,
Herreras Martinez Sara,
Lutz Martin,
Spek Anthony L.,
van Koten Gerard,
Klein Gebbink Robertus J. M.
Publication year - 2006
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.200600508
Subject(s) - chemistry , pincer movement , palladium , enantiopure drug , cationic polymerization , ligand (biochemistry) , medicinal chemistry , pincer ligand , coordination complex , stereochemistry , bromide , intramolecular force , crystal structure , diastereomer , magnesium bromide , catalysis , crystallography , polymer chemistry , organic chemistry , enantioselective synthesis , biochemistry , receptor , metal , magnesium
Neutral NCN‐pincer palladium bromide complex 2 containing the monoanionic, enantiopure pincer ligand 2,6‐bis{[( S )‐2‐hydroxymethyl‐1‐pyrrolidinyl]methyl}phenyl bromide ( 1 ) with bis‐ ortho ‐( S )‐prolinol substituents was synthesized and isolated as a mixture of three stereoisomers [( S N , S N , S C , S C ), ( R N , S N , S C , S C ), and ( R N , R N , S C , S C )] in a 1:1:1 ratio. Upon abstraction of the bromide ion from the unresolved mixture of 2 , single diastereoisomers of the cationic complexes [ 3 ]BF 4 and [ 3 ]PF 6 , respectively, were formed with a uniqueη 4 ‐ N , C , N , O coordination mode of ligand 1 . X‐ray crystal structure determination established the intramolecularη 4 ‐ N , C , N , O coordination of 1 to palladium where the typical mer ‐η 3 ‐ N , C , N pincer coordination is accompanied by coordination of one of the hydroxy groups of the ( S )‐prolinol moieties. The water molecule that was cocrystallized in the crystal structure of [ 3 ]PF 6 does not coordinate to palladium, but instead is involved in a hydrogen bonding network. The catalytic potential of both cationic complexes, [ 3 ]BF 4 and [ 3 ]PF 6 , was tested in an aldol reaction of aldehydes with methyl isocyanoacetate to yield the oxazoline products as racemic mixtures.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)