Synthesis of Tetraazabicyclic Ligands

Anhydrous CoCl₂, Co(OAc)₂, and NiCl₂ were purchased from Aldrich and used as received. Anhydrous Ni(OAc)₂ was prepared from Ni(OAc)₂·4H₂O (Fluka) dried under vacuum over refluxing ethanol in an Abderhalden drying pistol until a constant weight was reached, which corresponded to the loss of four equivalents of water.
4,11-Dibenzyl-1,4,8,11-tetraazabicyclo[6.6.2]hexadecane (1),²⁴ 4,10-dibenzyl-1,4,7,10-tetraazabicyclo[5.5.2]tetradecane (2),²⁴ 4-benzyl-11-methyl-1,4,8,11-tetraazabicyclo[6.6.2]hexadecane (3),^{16 (link)} and 4-benzyl-10-methyl-1,4,7,10-tetraazabicyclo[5.5.2]tetradecane (4),^{20 (link)} 4,11-dimethyl-1,4,8,11-tetraazabicyclo[6.6.2]hexadecane (5),²⁴ 4,10-dimethyl-1,4,7,10-tetraazabicyclo[5.5.2]tetradecane (6),^{25 (link)} and 1,4-bis((11-methyl-1,4,8,11-tetraazabicyclo[6.6.2] hexadecan-4-yl)methyl)benzene (7).^{16 (link)}