Synthesis, structure and reactivity of samarium complexes supported by Schiff-base ligands

Three tris(salicyladiminato) samarium complexes [3,5-Bu2t-2-(O)C6H2CHNAr′]3Sm(THF)n[Ar′=4-ClC6H4(1),4-CH3C6H4(2),8-C9H6N(quinoline)(3)] were synthesized by the reaction of anhydrous SmCl3 with the sodium salts of the Schiff-bases in THF in 3:1 molar ratio. X-ray diffraction studies revealed that the coordination geometry around samarium atom could be best described as a distorted pentagonal bipyramidal for complexes 1 and 2 and as a distorted tricapped trigonal prism for complex 3. It was found that the coordination environment around samarium atom has significant effect on the catalytic activity of homoleptic Schiff-base complexes of lanthanide. The increasing order of the catalytic activity for the ring-opening polymerization of ε-caprolactone, as well as guanylation of aniline with N,N-diisopropylcarbodiimide is 3 < 2 < 1.

Graphical abstractThree of homoleptic Schiff-base samarium complexes [3,5-Bu2t-2-(O)C6H2CHNAr′]3Sm(THF)n[Ar′=4-ClC6H4(1),4-CH3C6H4(2),8-C9H6N(quinoline)(3)] were prepared and structurally characterized. Complexes 1 and 2 showed moderate activity for the ring-opening polymerization of ε-caprolactone, as well as guanylation of aniline with N,N-diisopropylcarbodiimide, whereas complex 3 was almost inactive under the same reaction conditions.Figure optionsDownload full-size imageDownload as PowerPoint slide