Complexes formed by Zn II, Cd II and Hg IIin the presence of the octadentate ligand 1,4,7,10-tetrakis(pyrazol-1-ylmethyl)-1,4,7,10-tetraazacyclododecane. X-ray structure of the cadmium complex

Abstract

The potentially octadentate ligand 1,4,7,10-tetrakis(pyrazol-1-ylmethyl)-1,4,7,10-tetraazacyclododecane (L 1) yields with cadmium(II) compounds of formula [CdL 1]Y 2 (Y = BPh 4, ClO 4, PF 6) in which the metal ion is coordinated by the eight nitrogen donor atoms of the ligand. The crystal structure of [CdL 1] (BPh 4) 2 has been determined by X-ray diffraction. With zinc(II) and mercury(II) L 1 affords the compounds [ML 2]Y 2 [L 2 = 1,7-bis(pyrazol-1-ylmethyl)-1,4,7,10-tetraazacyclododecane. M = Zn; Y = ClO 4, PF 6. M = Hg; Y = PF 6] where the ligand L 2 originates from L 1 by loss of the methylpyrazole groups from two pendant arms of the macrocycle in trans positions. The compounds have been characterized by 1H and 13C NMR data. A variable temperature 13C NMR study on [CdL 1](PF 6) 2 suggests that the cation undergoes rearrangements in solution between two geometric isomers