Metal specific variable binding modes in Schiff base complexes — facile synthesis and crystal structure of anionic bis-N-(2-oxyethyl-5-bromosalicylal-diminato) cobalt(III)

The Schiff bases N-(2-hydroxyethyl)-X-salicylaldimine (X=H, Br) which show monobasic bidentate binding mode in their copper(II) complexes, in contrast offer dibasic tridentate chelation and almost spontaneous reaction leading to the synthesis of anionic bis-tridentate cobalt(III) chelates. On the other hand the Schiff bases N-(2-hydroxyphenyl)-X-salicylaldimine (X=H, Br) which are in dibasic tridentate binding mode in their copper(II) complexes are involved in monobasic bidentate chelation yielding neutral bis-bidentate cobalt(II) complexes. Crystal structure analysis of bis-N-(2-oxyethyl-5-bromosalicylal-diminato) cobalt(III) anion confirms near perfect octahedral geometry around cobalt(III).