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Studies have been conducted on the copper complexes formed with two sexadentate macrocyclic ligands containing four thioether sulfur donor atoms plus either two nitrogen or two oxygen donor atoms on opposing sides of the ring. The resulting two ligands, L, designated as [18]aneS4N2 and [18]aneS4O2, respectively, represent homologues of the previously studied Cu(ii/i) system with a macrocycle having six sulfur donor atoms, [18]aneS6. Crystal structures of [CuII([18]aneS4O2)](ClO4)2 and [CuI([18]aneS4O2)]ClO4 have been determined in this work. Comparison of the structures of all three systems reveals that the oxidized complexes are six coordinate with two coordinate bonds undergoing rupture upon reduction. However, the geometric changes accompanying electron transfer appear to differ for the three systems. The stability constants and electrochemical properties of both of the heteromacrocyclic complexes have been determined in acetonitrile and the CuII/IL electron-transfer kinetics have been studied in the same solvent using six different counter reagents for each system. The electron self-exchange rate constants have then been calculated using the Marcus cross relationship. The results are compared to other CuII/IL systems in terms of the effect of ligand geometric changes upon the overall kinetic behavior. [ABSTRACT FROM AUTHOR]

The activation of tris(dimethylamino)borane towards reaction with a chiral methimazole by N-methylimidazole has been used to prepare the first example of a chiral tris(methimazolyl)borate ligand. Coordination of this neutral ligand to Ru(ii) has been achieved by reaction with [(p-cymene)RuCl2]2 to provide a single diastereomer complex in which the chirality of the methimazolyl substituents dictate the chirality of the bicyclo[3.3.3]cage formed by the ligand on coordination to the metal. The alternative approach to chiral tris(methimazolyl)borate ligands involving the introduction of a chiral group onto the boron atom has been explored by replacing N-methylimidazole in the above reaction by chiral oxazolines as activating bases in reaction with simple methimazole. However, although the B(NMe2)3 is activated to reaction with methimazole by these oxazolines, an intramolecular oxazoline ring-opening by a coordinated methimazolyl sulfur occurs and prevents the successful synthesis of these ligands. [ABSTRACT FROM AUTHOR]