Mono-and Dinuclear Complexes of Chiral Tri-and Tetradentate Schiff-Base Ligands Derived from 1,1'-Binaphthyl-2,2'-diamine

摘要

The synthesis and characterization of the bis(bidentate)Schiff-base ligand [(R)-2] formed by the condensation reaction of(R)-1,1'-binaphthyl-2,2'-diamine [(R)-BINAM] with pyridine-2-carboxaldehyde is presented.The coordination chemistry of(R)-2 with Ni(CI0_4)_2(center dot)6H_20,Co(CI0_4)_2(center dot)6H_20,CuCI_2,and CuS0_4 has been investigated.Reaction of(R)-2 with the first two metal salts leads to complexes of the type [M((R)-4)_2](CI0_4)_2(M=Mi~II,Co~II),where(R)-4 is a tridentate ligand resulting from the hydrolytic cleavage of one of the pyridyl groups from(R)-2.Both complexes were characterized by X-ray crystallography,which showed that the A absolute configuration of the metal center is favored in both cases.1H NMR spectroscopy suggests that the high diastereoselectivity of A-[Co((R)-4)2](CI04)2 is maintained in solution.The reaction of(R)-2 with CuCI_2 leads to the dinuclear complex [Cu_2((R)-2)CI_4],which has a [Cu_2(mu~2-CI_2)] core.The reaction of CuS0_4 with(R)-2 gives a dimeric complex,{Cu((R)-4)S0_4}_2,which features a [Cu_2(mu~2-(S0_4)_2)] core.This complex can be prepared directly by the reaction of(R)-BINAM with pyridine-2-carboxaldehyde and CuS0_4.The use of rac-BINAM in this synthetic procedure leads to the heterochiral dimer [Cu_2((R)-4)((S)-4)(S0_4)_2];that is,the ligands undergo a self-sorting(selfonself discrimination)process based on chirality.The reaction of rac-BINAM,pyridine-2-carboxaldehyde,and Co(CI0_4)_2(center dot)6H_20 proceeds via a homochiral self-sorting pathway to produce a racemic mixture of [Co((R)-4)_2]~(2+)and [Co((S)-4)_2]~(2+).The variable-temperature magnetic susceptibilities of the bimetallic complexes [Cu_2((R)-2)CI_4],[Cu((R)-4)(mu~2-S0_4)]_2,and [Cu_2((R)-4)((S)-4)-(mu~2-S0_4)_2] all show weak antiferromagnetic coupling with J=-1.0,-0.40,and-0.67 cm~(-1),respectively.