Synthesis, spectral and thermal behavior of two novel complexes of Cr(III) with dibromobenziloxime

Abstract

The reaction of 4,4′-dibromobenzilmonoxime (BBOH) with CrCl3·6H2O in DMF gives the mono nuclear Cr(III) complex, [Cr(BBO)3] (1). Reaction of complex (1) with a methanolic solution of KOH at room temperature leads to a dinuclear Cr(III)–Cr(III) complex, [Cr(BBO)2(OH)]2 (2). Both complexes were characterized on the basis of their elemental analysis, molar conductivity, Mass, IR, electronic spectra, and thermal analysis methods in addition to magnetic susceptibility technique. These studies suggest that oxime ligand is bonded to Cr(III) ions through the oxygen atom of the carbonyl, and the nitrogen atom of the oxime groups. In addition, the presence of a hydroxo bridge in the dimeric complex (2) is inferred from the IR spectral studies. The electronic spectral data of both complexes are in good agreement with the octahedral coordination of Cr(III) ion. The electronic spectra of the complexes revealed two bands due to d–d transitions, and one band assignable to an oxygen (p π) → Cr(e g *) LMCT transition observed in both Cr(III) complexes. An additional charge transfer transition, assignable to μ–OH(p π) → Cr(e g *), was only observed for the dimeric Cr(III) complex (2). The ligand field parameters for these complexes, i.e., splitting energy and Racah parameter were calculated to be 18,382 and 557 cm−1 for [Cr(BBO)3] (1), 18,248 and 553 cm−1 for [Cr(BBO)2(OH)]2 (2) respectively. The reaction of 4,4′-dibromobenzilmonoxime (BBOH) and CrCl3·6H2O in DMF has yielded the monomeric complex [Cr(BBO)3]. Addition of KOH to this monomeric complex afforded the dimeric complex [Cr(BBO)2(OH)]2.