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

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.