Forced ether oxygen coordination from reduced Schiff base ligand in [Cu2 ] complexes : Synthetic preference, trapping of carboxylates and catechol oxidation

Department of Chemistry, Indian Institute of Technology, Kharagpur-721 302, West Bengal, India E-mail : dray@chem.iitkgp.ernet.in Fax : 91-3222-82252 Phenol-centered heptadentate ligand H5L bearing two adjacent and flexible amine-ether-alcohol arms enforced ether oxygen coordination in [Cu2 (µ-H4L 2 )2 ](CH3CO2 )2 (1) and [Cu2 (µ-H4L 2 )2 ](HCO2 )2 (2). Dangling ligands arms were used to entrap carboxylate anions. Probable high nuclearity [Cu4 ] complexes were not formed due to the removal of acetate and formate anions from the first coordination sphere. Coordination of ether oxygen in apical position was possible due to enhanced flexibility of the ligand arms through imine reduction. X-Ray structure determination and analysis of Hirshfeld surfaces indicated the synergistic role of crystal packing and hydrogen bonding interaction for supramolecular trapping of carboxylates. Functional behavior in MeOH : MeCN (1 : 10) medium showed that complex 1 is more efficient than complex 2 for catechol oxidation