Synthesis, structure, and catalytic activity of new aluminum and titanium complexes based on aminobisphenolate ligands containing bulky substituents

A reaction of aminobisphenols EtN{CH 2 [(4-Alk)(6-But)(2-HO)C 6 H 2 ]} 2 , Alk = Me ( 1 ); Bu t ( 2 ) containing alkyl substituents in the phenol groups with trimethylaluminum and tetra( tert -butoxy)titanium gave two new aluminum derivatives with the Me–Al bond: EtN{CH 2 [(2-Alk)-(4-Bu t )C 6 H 2 (2-O–)]}2Al–Me, Alk = Me ( 3 ); Bu t ( 4 ), and two new titanium derivatives with the Bu t O–Ti bond: EtN{CH 2 [(2-Alk)(4-Bu t )C 6 H 2 (2-O–)]}2Ti(O–Bu t ) 2 , Alk = Me ( 5 ); But ( 6 ). The structures of new compounds were confirmed by NMR spectroscopy and elemental analysis. The structures of complexes 3 and 6 were studied by X-ray crystallography. Complexes 3 and 6 are monomeric in the solid phase: a coordination number of Al atom is 4 , that of Ti atom is 5 , in addition to the M–O bonds the M←N interactions are also present. Complexes 3–6 were studied as initiators of the ring-opening polymerization of ε-caprolactone. The resulting polymers are characterized by relatively high values of number average molecular weight, with the polydispersity being relatively low.