Dimeric samarium(III) alkoxides bearing N2O2 tetradentate Schiff bases and their utility for the catalytic epoxidation of trans-chalcone

Two anhydrous, dimeric samarium(III) complexes bearing a bulky μ-alkoxide (diphenylmethoxide) ligand and different “saturated” tetradentate Schiff bases {bis-5,5′-(1,3-propanediyldiimino)-2,2-dimethyl-4-hexene-3-onato and bis-5,5′-(2,2-dimethyl-1,3-propanediyldiimino)-2,2-dimethyl-4-hexene-3-onato} were synthesized and fully characterized. The complexes differ only in alkyl substitution at the three-carbon amino linker between the ketoiminato halves, with one having a CH2 group and the other a C(CH3)2 substituent along the free-ligand idealized mirror plane. Both metal-containing molecules were isolated in high-yields from direct alcoholysis of the corresponding 5-coordinate, mononuclear complexes and their catalytic activity for the epoxidation of 1,3-diphenyl propenone (trans-chalcone), an α,β-unsaturated ketone, investigated.