N-Methylation of macrocyclic hexaaminecobalt(III) complexes
Abstract
Reaction between formaldehyde and the pendant arm macrocyclic complex (trans-6,13-dimethyl-1,4,8,11-tetraazacyclotetradecane-6,13-diamine)cobalt(III) [CoL1]3+ yielded the diimine derivative trans-6,13-dimethyl-6,13-bis(methyleneamino)-1,4,8,11-tetraazacyclotetradecane (L3) as its cobalt(III) complex. Reduction of the imines has been achieved with NaBH4 and the meso and rac cobalt(III) complexes of trans-6,13-dimethyl-6,13-bis(methylamino)-1,4,8,11-tetraazacyclotetradecane (L5) have been prepared. Crystal structures of the macrocyclic complexes [CoL1][ClO4]3, [CoL3][ClO4]3 and meso-[CoL5][ClO4]3·2H2O were determined and some unusual structural, spectroscopic and electrochemical variations observed going from the parent hexaamine [CoL1]3+ to [CoL3]3+ (diimine) and ultimately to [CoL5]3+ (bis-N-methylated hexaamine).