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Predetermined Chirality at Metal Centers of Various Coordination Geometries: A Chiral Cleft Ligand for Tetrahedral (T‐4), Square‐Planar (SP‐4), Trigonal‐Bipyramidal (TB‐5), Square‐Pyramidal (SPY‐5), and Octahedral (OC‐6) Complexes
Author(s) -
Mamula Olimpia,
von Zelewsky Alex,
Bark Thomas,
StoeckliEvans Helen,
Neels Antonia,
Bernardinelli Gérald
Publication year - 2000
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/1521-3765(20001002)6:19<3575::aid-chem3575>3.0.co;2-#
Subject(s) - octahedron , tetrahedron , square (algebra) , square pyramidal molecular geometry , crystallography , chirality (physics) , trigonal bipyramidal molecular geometry , planar , planar chirality , ligand (biochemistry) , metal , materials science , chemistry , physics , geometry , crystal structure , mathematics , quantum mechanics , enantioselective synthesis , chiral symmetry , metallurgy , computer science , biochemistry , nambu–jona lasinio model , computer graphics (images) , receptor , quark , catalysis
Two tetradentate bis‐pinene–bipyridine type ligands, each with six stereogenic carbon centers, were synthesized from (−)‐α‐pinene. Their ability to predetermine chiral configurations at metal centers was studied. The two diastereoisomers, L1 and L2 , differ in their absolute configuration at the bridgehead position. These ligands form metal complexes with Ag I , Pd II , Zn II , Cu II , and Cd II , with coordination numbers four, five, and six and with complete control of chirality at the metal centers. Using L1 rather than L2 leads to complexes of inverted absolute configuration at the metal centers. These diastereomeric coordination species can be obtained either as separate compounds or, in some cases, as solids containing them in a 1:1 ratio. Ligands L1 and L2 thus show that the pinene–bipyridines are versatile molecules for the formation of metal complexes with predetermined chirality. In all cases, absolute configurations were determined in the solid state by X‐ray diffraction methods and in solution by CD spectroscopy. The sign of exciton couplets from the π–π* transitions always agrees with the expectations for a given local configuration at the metal center. The five‐coordinate, inherently chiral species of Zn II and Cu II described in this article are the first examples of trigonal‐bipyramidal metal complexes with predetermined absolute configuration containing topologically linear ligands.