Copper complexes mixed ligands

The stability constants of the copper(n) mixed-ligand complexes with 6-deoxy-6-(N-histamino)-P-cyclodextrin 1 (CDhm) and aliphatic or aromatic amino acids [39] are reported in Table I. 

Thus the results from the studies of copper bis-dithiocarbamate complex reactions with tin(22) antimony(22) and copper(23) halides show formation of copper(II) mixed-ligand complexes. 

Crystal stmctures of complexes of copper(II) with aromatic amine ligands and -amino acids " " and dipeptides" have been published. The stmctures of mixed ligand-copper complexes of L-tryptophan in combination with 1,10-phenanthroline and 2,2 -bipyridine and L-tyrosine in combination with 2,2 -bipyridine are shown in Figure 3.2. Note the subtle difference between the orientation of the indole ring in the two 1,10-phenanthroline complexes. The distance between the two... 

J. and Bernal, 1. (2004) A critical look on the nature of the intra-molecular iriterligarid Jt,Jt-stackrng interaction in mixed-ligand copper(II) complexes of aromatic side-chain amino acidates and a,a -diimines. Cryst Eng Comm, 6, 627. 

Ligand exchange has proved to be very successful in the separation of several enantiomers. Davankov and Rogozhin (41) used chiral copper complexes bonded to silica. The enantiomeric separation is based essentially on the formation of diastereomeric mixed complexes with different thermodynamic stabilities. It is generally accepted that chiral discrimination proceeds via the substitution of one ligand in the coordination sphere of the metal ion. Ligand exchange technique is especially effective for the enantiomeric resolution of aminoacids, aminoacids derivatives, and hydroxy acids (42). 

Substantial rate accelerations are observed in these systems for base hydrolysis. Thus for the ethylenediamine complex (18) rate increases of 4x 104 for GlyOEt to 1.4 x 107 for ethyl picolinate are observed.85 These rate accelerations are consistent with the formation of carbonyl-bonded species (18). The effects with methyl L-cysteinate and methyl L-histidinate are much less marked as such ligands can give mixed ligand complexes which do not involve alkoxycarbonyl donors. Thus in the case of methyl L-histidinate the complex (20) is formed. For these latter two esters only relatively small rate accelerations of 20-100 occur. For the chelate ester complexes, the ratios of kcm/kH2o fail within the range 3.8 x 109 to 3.2 x 1011. Such values for the relative nucleophilicity of water and hydroxide ion are comparable with those previously noted for copper(II) complexes.82... 

The ICC of the examined type with alkylamine substituents (X — O, Y — K, R = Aik, m = 2) have been studied for a long time [137,206]. The majority of them are represented by hexacoordinated structures 870. Structurally characterized copper complex 885 (M = Cu, X — O, Y = N, R = Me, m = n = 2) is an example of complexes with CN = 5 [213]. The indicated substituent at the imine nitrogen atom participates by coordination in structurally characterized mixed-ligand complex 890 obtained according to Scheme (4.53) [214] ... 

Scheme 13. Synthesis of mixed ligand yttrium/copper complexes [137]...

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