Mixed Ligand Complexes with Diamines

each chloride was extracted from each of the former three fractions by shaking repeatedly with water and isolated as solids by evaporating the solution and then by adding ethanol. After repeated chromatography A-[Co(R-pn)3]Cl3, A-[Ct en -(R-pn)2]Cl3 2 H2O and A-[Co(en)2(R-pn)]Cl3 H2O were obtained as pure compounds. 

At the same time, Dwyer et al. determined equilibrium concentrations for the isomers in the reaction mixtures with varied molar ratios of en/pn. For en/pn = 1/2, the paper chromatography on Whatman 3 MM with 5ec-Bu0H H20 10 mol/dm HCl (70 20 10), the separated bands corresponded to A-[Co(R-pn)3fA-[Co(en)-(R-pn)2p , A-[Co(en)2(R-pn)] and A-isomers + [Co(en)3p . The last fraction was rechromatographed on a paper with n-BuOH H2O 60% HCIO4 (70 20 10), four bands being completely separated. The experiment of en/pn = 2/1 was carried out 

The cellulose column chromatography was soon applied to equilibrium mixtures of the complexes with R,S-propylenediaminethe first fraction contained A(+)[Co(S-pn)3f and A(—)[Co(R-pn)3f the second fraction A(+)[Co(S-pn)2- 

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Heterocyclic nitrogen donors and their adducts with zinc chloride have been studied.623,624 A large number of other ligand systems have also been characterized, for example, zinc halide adducts of 2,2-dimethylpropane-1,3-diamine and hexamethylphosphoramide have been studied.625,626 The formation of mixed ligand complexes with chloride and substituted pyridines has been studied.627 The zinc tris(pyridyl) chloride anion has also been structurally characterized.628 Manganese(II) ions have been used to probe the stereochemistry in reactions of zinc halides with pyrazine.629... 

Chelating diamines eg diaminoethane (en) or diaminopropane (pn) form complexes when mixed with cobalt(II) salts in presence of an oxidant. Mixed ligand complexes may be also prepared in presence of a second ligand. 

An example of recognition of nucleotides through formation of mixed complexes with polyamine ligands is provided by the system Cu +-4,7,10,13-tetrazahexadecane-1,16-diamine (100)- AMP (Scheme 21) ... 

In initial work [37], we demonstrated that complexes containing different imine ligands could be synthesized in each others presence. When pyridine-2-carbaldehyde and benzaldehyde-2-sulfonate were mixed in aqueous solution with the diamine shown in Scheme 1.9, a library of ligands is created in dynamic equilibrium with the starting materials. The addition of copper(I) eliminated all but two of these ligands, forming complexes 8 and 9 in quantitative yield [37]. 

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