Synthesis, structural diversity, supramolecular architecture, and catalytic reactions of mononuclear and heteronuclear benzamide cobalt complexes

Abstract

Two NNN-type benzamide derivative ligands {N,N'-(2,2′-azenidiyl-bis(2,1-phenylene))dicyclohexanecarboxamide (H3LcyHex) and N,N'-(2,2′-azenidiyl-bis(2,1-phenylene))dicyclobutanecarboxamide (H3LcyBu)} that incorporate N-amidate donors have been synthesized and characterized by 1H NMR, 13C NMR, and FT-IR techniques. Subsequently, heterometallic trinuclear cobalt-potassium complexes, [K2(DMF)6Co(HL)2] (KCyBu and KCyHex) and mononuclear cobalt complexes with complementary tetraethylammonium ions, [Et4N]2[Co(HL)2] (ECyBu and ECyHex), both incorporating these ligands, have been synthesized. Suitable crystals for single-crystal X-ray diffraction of H3LcyHex and KCyBu have been characterized using single-crystal X-ray diffraction analysis. Intermolecular interactions play a major role in the formation of the supramolecular architecture in the crystal lattice of compounds. The supramolecular structures in H3LcyHex are formed through intermolecular CH⋅⋅⋅O, CH⋅⋅⋅π, CH⋅⋅⋅O/N, and CH⋅⋅⋅N interactions, and those in KCyBu are generated by CH⋅⋅⋅π and CH⋅⋅⋅O intermolecular interactions. The amphoteric properties exhibited by new cobalt-oxygen species produced through the reaction of cobalt complexes with molecular oxygen were examined by their electrophilic reactivity in the conversion of triphenylphosphine (PPh3) to triphenylphosphoxide (OPPh3) and their nucleophilic reactivities in the deformylation reaction of 2-phenylpropionaldehyde (2-PPA) to acetophenone (catalyst/substrate ratio, 1:100). In the catalytic activity results, it was observed that the cobalt-oxygen complexes have an amphoteric feature due to their good reactivity in both reactions.