Non-template synthesis of new tetra-aza macrocyclic ligands and their cobalt, nickel, and copper complexes: X-ray structure of (5,14,15,16,17,18-hexahydro-7-methyldibenzo[b,i][1,4,8,11]tetra-azacyclotetradecinato) nickel(II) monoperchlorate

Abstract

Reaction of the open-chain tetramines 1,3-bis(o-aminophenylamino)propane (L) or 1,3-bis(o-amino-p-methylphenylamino)propane (L′) with 3-ethoxy-2-methylacrolein gives the title macrocycle, HL¹, or its methyl substituted derivative, HL², in yields of the order of 40% without recourse to either high dilution or metal template techniques. Reaction of HL¹ or HL² with Co^II, Ni^II, or Cu^II salts is accompanied by deprotonation of the ligand and its co-ordination to the metal ion as a monoanionic species. The X-ray structure of [NiL¹][ClO₄](1) confirms the site of deprotonation and establishes the square planar geometry of the metal ion. Treatment of [NiL¹][ClO₄] with NEt₃ in air results in oxidative dehydrogenation of the ligand and the isolation of [Ni(C₁₉H₁₆N₄)]. Crystals of (1) are triclinic, space group P, with a= 12.351(3), b= 10.596(3), c= 7.841(3)Å, α= 91.971(3), β= 92.654(3), γ= 108.978(3)°, and Z= 2.