COMPLEXES FORMED BY ZN-II, CD-II AND HG-II IN THE PRESENCE OF THE OCTADENTATE LIGAND PYRAZOL-1-YLMETHYL)-1,4,7,10-TETRAAZACYCLODODECANE - X-RAY STRUCTURE OF THE CADMIUM COMPLEX

The potentially octadentate ligand 1,4,7,10-tetrakis(pyrazol-1-ylmethy l)-1,4 dodecane (L-1) yields with cadmium(II) compounds of formula [Cd L1]Y-2 (Y = BPh4, ClO4, PF6) in which the metal ion is coordinated by the eight nitrogen donor atoms of the ligand. The crystal structure of [CdL1] (BPh,), has been determined by X-ray diffraction. With zinc(II ) and mercury(II) L-1 affords the compounds [ML2]Y-2 [L-2 = yrazol-1-y lmethyl)-1,4,7,10-tetraazacyclododecane. M = Zn; Y = ClO4, PF6. M = Hg ; Y = PF6] where the ligand L-2 originates from L-1 by loss of the met hylpyrazole groups from two pendant arms of the macrocycle in trans po sitions. The compounds have been characterized by H-1 and C-13 NMR dat a. A variable temperature C-13 NMR study on [CdL1](PF6)(2) suggests th at the cation undergoes rearrangements in solution between two geometr ic isomers. (C) 1997 Elsevier Science Ltd.