Cobalt(III) complexes with racemic polyamine ligands 1. Isomers formed using 5,5,7(R,S),12,12,12,14(R,S)-hexamethyl-1,4,8,11-tetraazacyclotetradecane (tetb) |
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Affiliation: | 1. Department of Radiology, Shanghai Jiao Tong University Affiliated Sixth People''s Hospital, Shanghai 200233, China;2. Radboud University, Institute for Molecules and Materials, Heyendaalseweg 135, 6525 AJ Nijmegen, the Netherlands;3. State Key Laboratory of Chemical Engineering and Shanghai Key Laboratory of Multiphase Materials Chemical Engineering, East China University of Science and Technology, Shanghai 200237, China |
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Abstract: | cis-[Co(ox)(tetb]ClO4 is readily isolated from the reaction between tetb (tetb = rac-Me6-cyclam = 5,5,7(R,S),12,12,14(R,S)-hexamethyl-1,4,8,11-tetraazacyclotetradecane) and K3Co(ox)3·3H2O in aqueous solution. Removal of the coordinated oxalato ligand by acid hydrolysis (with HCl/HClO4) results in the formation of α-trans-(RRRR,SSSS), [CoCl2{(SSeq,RReq)-tetb}]ClO4 with both six-membered rings in the twist conformation. The (RR)-(+)-tartrate (−2) ion coordinates enantioselectively with this isomer to give (–)-cis-[Co2{μ-(RR)-(+)-(tart)}{(RR)-tetb}2](ClO4)2 and this, in turn, reacts with HCl/HClO4 to give (–)-α-trans-(1S,4S,8S,11S)-[CoCl12{7Req,14Req)-tetb}]ClO4. The absolute configuration of the tetraamine obtained in the resolution procedure was established by synthesizing the α-trans-dichloro isomer using tetb of known absolute configuration. |
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