Mono and bimetallic CoIII Schiff base complexes: Coordination induced ligand imidazolidine ring cleavage and stabilization

2-(2′-Hydroxyphenyl) imidazoline ring grafted dinucleating diimine-diamine-tris-phenol ligand (H3aeas) has been obtained from a two-step reaction of 2-hydroxy acetophenone, N,N′-bis-(2-aminoethyl)ethylenediamine and 2-hydroxy benzaldehyde. Reaction of the ligand with Co(ClO4)2·6H2O and NEt3 in MeOH–DCM solvent mixture yielded the monometallic complex [Co(aea)]ClO4·H2O (1) of imidazolidine ring hydrolyzed hexadentate proligand H2aea. Any solvent derived MeO− bridged Co2 complex could not be obtained due to facile cobalt coordination assisted hydrolytic cleavage of substituted imidazolidine ring. When the reaction is carried out with Co(NO3)2·4H2O and CoCl2·6H2O in presence of NH4NCS and NaN3 in MeOH–DCM and MeOH under aerobic conditions, preassembly of bimetallic [Co2(μ-OMe)]5+ and [Co2(μ-N3)]5+ cores takes place on the solvent derived methoxido and azido clips through non-hydrolytic pathways in [(SCN)2Co2(μ-OMe)(μ-aeas)]·DMF (2), and cocrystals of [(N3)2Co2(μ-OMe)(μ-aeas)] (3a) and [(N3)2Co2(μ-N3)(μ-aeas)] (3b), respectively.

Stabilization and hydrolytic cleavage of imidazolidine ring in a binucleating ligand aeas3− were examined in the presence and absence of NH4NCS and NaN3 in MeOH–DCM and MeOH solvent media with Co(NO3)2·4H2O, CoCl2·6H2O and Co(ClO4)2·6H2O.Figure optionsDownload as PowerPoint slideHighlights
► Reactivity and cobalt ion coordination with a binucleating ligand.
► Coordination induced cleavage and stabilization of substituted imidazolidine ring.
► Crystal structure of mono and dinuclear complexes of cobalt.
► Synthesis of dicobalt complex in presence of NH4SCN and NaN3.