Syntheses, characterizations and structures of organometallic tri- and tetra-dentate ferrocenoyl enaminone ligands and their unsymmetrical Schiff base derivatives

Abstract

Condensation of ferrocenoylacetone with alkyl or aryl diamine (1,2-diaminoethane, 1,3-diaminopropane, 1,4-diaminocyclohexane, 1,4-diaminobenzene) afforded three tridentate ferrocenoyl enaminone ligands (Fc–C(O)CHC(CH3)NHR1) (L1: R1 = CH2CH2NH2; L3: R1 = 4-C6H4NH2; L5: R1 = 4-C6H10NH2; Fc = ferrocenyl) and four symmetrical tetradentate ferrocenoyl enaminone ligands [(Fc–C(O)CHC(CH3)NH]2R (L2: R = CH2CH2; L4: R = 4-C6H4; L6: R = 4-C6H10; L8: R = CH2CH2CH2). Of which, L3 was further reacted with appropriate substituted salicylaldehydes to give unsymmetrical Schiff base ligands Fc–C(O)CHC(CH3)NH(4-C6H4)NCH(2-OHAr) (L9: Ar = C6H4; L10: Ar = 5-ClC6H3; L11: Ar = 5-NO2C6H3; L12: Ar = 3,5-Br2C6H2; L13: Ar = 3,5-tBu2C6H2). All new ligands L3∼L6, L8 and L9∼L13 were characterized by 1H NMR, 13C NMR, FT-IR, and UV–Vis spectroscopies along with their electrochemical properties. Moreover, molecular structures of ligands L2∼L4, L8 and L9 have been established by single-crystal X-ray crystallography.