Synthesis and characterisation of pendant-arm alcohol derivatives of [9]aneN2S and complexation with CuII ([9]aneN2S = 1-thia-4,7-diazacyclononane)†

Abstract

An improved detosylation of 4,7-bis(tolyl-p-sulfonyl)-1-thia-4,7-diazacyclononane to give the free amine [9]aneN₂S has been accomplished using Li/NH₃ or HBr/acetic acid. Reaction of [9]aneN₂S with ethylene oxide, 1,1-dimethylethylene oxide and methylenecyclohexane oxide in alcoholic solution affords the potentially pentadentate ligands 4,7-bis(hydroxyethyl)-1-thia-4,7-diazacyclononane (H₂L¹), 4,7-bis(2-hydroxy-2-methylpropyl)-1-thia-4,7-diazacyclononane (H₂L²) and 4,7-bis(2-cyclohexyl-2-hydroxymethyl)-1-thia-4,7-diazacyclononane (H₂L³) respectively. The copper(II) complexes of these ligands have been prepared and reveal that increasing the steric bulk on the pendant arm has a marked effect upon the resultant co-ordination chemistry. Thus, the complex of H₂L¹ shows a dimeric structure [Cu₂(HL¹)₂][PF₆]₂ 1 in which one of the hydroxy groups has been deprotonated. With H₂L² two complexes can be isolated: the dimer [Cu₂(HL²)₂][PF₆]₂ 2 and the monomer [Cu(HL²)][PF₆] 3. In contrast, with H₂L³ only the monomer [Cu(HL³)][PF₆] 4 could be isolated. Single crystal structures of 1 and 3 have been determined. Magnetochemistry of 1 indicates that the two copper(II) centres are essentially non-coupled.