Syntheses and Properties of Tris[1-(p-substituted phenyl)-1, 3butanedionate]cobalt(III) Complexes

Abstract

The cobalt (III) complexes, CoL3, were synthesized with 1-(p-substituted phenyl) -1, 3-butanediones (HL, L=p-XC₆H₄COCHCOCH₃, X=NO₂[1], COOH[2], COOCH₃[3], Br[4], C1[5], H[6], NHCOCH₃[7], C₂H₅[8], CH₃[9], OCH₈[10], OH[11]), and were separated into the fac and mer isomers by column chromatography on alumina. The ¹H-NMR spectra of CH₃ and CH exhibited a single peak for the fac isomer, and three p2eaks for the mer isomer. The chemical shifts of CH₃ and CH protons in chloroform-d and benzene-d₆ were observed at 1.9-2.4 ppm and 5.9-4.3 ppm, respectively, and the substituent effect and solvent effect for both protons were investigated. The ligand field bands, v₁(³T_1g←¹A_1g) and v3(¹T_1g←¹A1_1g) shifted linearly to the higher frequency side as the substituents became more electro n donative. The stability of these complexes was found to increase in the order of[1]<[2]<[3]<[4]<[5]<[6]=[7]<[8]<[9]<[10]<[11]in terms of the crystal field splitting energy 10 Dq obtained from the ligand field bands.