Template synthesis of amidine- and amide-functionalised cobalt(III) hexaaza cage complexes

Abstract

The reaction of [Co(sen)]Cl₃·H₂O {sen = 4,4′,4′′-ethylidynetris(3-azabutan-1-amine)} with methanal and ethyl cyanoacetate in aqueous base led to the synthesis of three functionalised cobalt(III) cage complexes: (1-cyano-8-methyl-2-oxo-3,6,10,13,16,19-hexaazabicyclo[6.6.6]icosanato)cobalt(III) chloride–water(1/3) [Co(CN,Me-2-oxosar − H)]Cl₂·3H₂O; (2-amino-1-carboxy-8-methyl-3,6,10,13,16,19-hexaazabicyclo[6.6.6]icos-2-ene)cobalt(III)]trichloride–ethanol–water(1/0.5/3.5), [Co(Me,CO₂H-2-aminosar-2-ene)]Cl₃·0.5C₂H₅OH·3.5H₂O; and (2-amino-8-methyl-3,6,10,13,16,19-hexaazabicyclo[6.6.6]icos-2-ene)cobalt(III) trichloride–water(1/3), [Co(Me-2-aminosar-2-ene)]Cl₃· 3H₂O. The amidine-functionalised cages are the first hexaaza cages of that type. The structure of [Co(CN,Me-2- oxosar − H)][ClO₄]_3/2Cl_1/2·H₂O has been established by X-ray crystallographic analysis. The syntheses, chemical reactions and spectroscopic and electrochemical properties of the cage complexes are described.