Template synthesis of N-aminoethylated hexaaza macrobicyclic nickel(II) complexes containing one four-membered chelate ring

✍ Scribed by Shin-Geol Kang; Kiseok Ryu; Soo-Kyung Jung; Jong Hwa Jeong

• Book ID: 104138457
• Publisher: Elsevier Science
• Year: 2001
• Tongue: English
• Weight: 116 KB
• Volume: 317
• Category: Article
• ISSN: 0020-1693
• DOI: 10.1016/s0020-1693(01)00347-4

✦ Synopsis

New nickel(II) complexes of the hexadentate macrobicycles 6-(2-aminoethyl)-1, 3,6,9,11,14-hexaazabicyclo[12.3.1] 3,6,9,11,14-hexaazabicyclo[12.2.1]heptadecane (2), and 6-(2-aminoethyl)-1, 3,6,9,11,15-hexaazabicyclo[13.3.1]nonadecane (3) have been prepared selectively by the metal template condensation of formaldehyde with tris(2-aminoethyl)amine and a triamine (1,4,8-triazaoctane, 1,4,7-triazaheptane, or 1,5,9-triazanonane). The complexes [Ni(L)] 2 + (L =1, 2, or 3), in which one 2-aminoethyl pendant arm is coordinated to the metal ion, have distorted octahedral coordination geometry with a rarely observed four-membered chelate ring. They are extremely stable in neutral or basic aqueous solutions but are readily decomposed in acidic conditions. The decomposition rate of the complexes in HClO 4 solutions is not affected significantly by the ring size of the macrobicyclic ligands. Synthesis and characterization of the nickel(II) complexes are reported, together with the crystal structure of [Ni(1)][ZnCl 4 ].