Synthesis, characterization and catalytic studies of aluminium complexes containing sulfonamido–oxazolinate or –pyrazolinate ligands

•Several aluminium sulfonamido–oxazolinate or –pyrazolinate complexes have been prepared.•Complexes bearing sulfonamido–pyrazolinate ligands show better activities towards ROP.•Poor activities towards ROP might result from the steric effect on the pyrazolyl ring.

A series of sulfonamido–oxazolinate ligand precursors, HNSO2PhHOxa, HNSO2PhMeOxa, HNSO2PhTriMeOxa, or sulfonamido–pyrazolinate ligand precursors, HNSO2PhHPzH, HNSO2PhMePzH, HNSO2PhTriMePzH, HNSO2PhFPzH, HNSO2PhHPzMe, HNSO2PhMePzMe, HNSO2PhTriMePzMe, have been prepared. Treatment of ligand precursors, HNSO2PhAOxa or HNSO2PhAPzB, with 1.1 equiv. of AlMe3 in THF affords aluminium sulfonamido–oxazolinate dimethyl complexes, (NSO2PhAOxa)AlMe2 [A = H (1); A = Me (2); A = TriMe, (3)], or aluminium sulfonamido–pyrazolinate dimethyl complexes, (NSO2PhAPzB)AlMe2 [A = H, B = H (4); A = Me, B = H (5); A = TriMe, B = H (6); A = F, B = H (7); A = H, B = Me (8); A = Me, B = Me (9); A = TriMe, B = Me (10)]. The aluminium bis(sulfonamido–pyrazolinate) methyl complex 5′ was isolated from recrystallization of 5 as minor product. The molecular structures of compounds 2, 5′ and 8 were determined by single-crystal X-ray diffraction techniques. Their catalytic activities towards the ring opening polymerization of ε-caprolactone in the presence of benzyl alcohol are also under investigation.

Graphical abstractA series of aluminium dimethyl complexes bearing sulfonamido–oxazolinate or sulfonamido–pyrazolinate ligands has been prepared. They exhibit catalytic activities towards the ring opening polymerization of ε-caprolactone in the presence of benzyl alcohol.Figure optionsDownload full-size imageDownload as PowerPoint slide