Synthesis and co-ordination chemistry of 1,5,9-triazacyclododecane monosubstituted with imidazole and pyrazole

Abstract

The potentially tetradentate ligands 1-(imidazol-4-ylmethyl)- (L ¹ ), 1-(1-methylimidazol-2-ylmethyl)- (L ² ) and 1-(pyrazol-3-ylmethyl)-1,5,9-triazacyclododecane (L ³ ) have been synthesized; L ¹ was isolated as the tetrahydrochloride, L ¹ ·4HCl. The basicity constants of L ¹ and L ³ have been determined by potentiometry at 25 °C in NaCl. The co-ordination chemistry of L ¹ and L ³ toward some 3d metal ions has been investigated and the complexes [ML ³ (Cl)]Y (M = Mn or Fe, Y = BPh ₄ ; M = Ni, Y = BF ₄ ) and [ML(ClO ₄ )]BPh ₄ (M = Co, L = L ³ ; M = Cu or Zn, L = L ¹ or L ³ ) have been isolated and characterized. The structures of the iron(II) and nickel(II) complexes of L ³ have been determined by single-crystal X-ray analyses. Both contain dimeric [{ML ³ (Cl)} ₂ ] ²⁺ complex cations in which each metal ion is six-co-cordinated by four nitrogen donors of one L ³ ligand and by two bridging Cl ^- ions in an approximately octahedral environment.