Stability constants of copper(I) and silver(I) complexes with open-chain, macrocyclic and -bicyclic aza-ligands in acetonitrile and comparison with results in dimethylsulfoxide

Stability constants of copper(I) and silver(I) with butylamines, monoaza- a nd diaza-crown ethers and cryptands have been determined in acetonitrile (A N). The stability constants of the silver(I) complexes are markedly larger than those with copper(I), and the complexation behaviour of silver(I) is d etermined to a much larger extent by the tendency to form inclusion complex es involving interactions with both, oxygen and nitrogen donor atoms. Silve r(I) forms only 1:1 inclusion complexes with macrobicylic cryptand ligands, for example, whereas copper(I) additionally forms 2:1 (Cu+:ligand) complex es in which the cryptands act as monodentate ligands. A comparison of the r esults in AN with those reported in dimethylsulfoxide (N. Heidari, A. Thale r, H. Schneider, B.G. Cox, Inorg. Chim. Acta 279 (1998) 186) shows that in cryptand complexes the cation is normally well shielded from interactions w ith the solvent, such that the free energies of transfer of the ligands and cryptates are very similar. All other complexes show evidence of residual interactions of the complexed cations with the solvent. The observed differ ence between the complexation reactions of silver(I) and copper(I) in AN an d in the responses of their complex stabilities to solvent transfer, can be attributed to different preferences of the two cations for binding with ni trogen and oxygen atoms; copper(I) in particular shows a very strong prefer ence for nitrogen donor atoms. (C) 1999 Elsevier Science S.A. All rights re served.