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

A reaction of aminobisphenols EtN{CH2[(4-Alk)(6-But)(2-HO)C6H2]}2, Alk = Me (1); But (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{CH2[(2-Alk)-(4-But)C6H2(2-O–)]}2Al–Me, Alk = Me (3); But (4), and two new titanium derivatives with the ButO–Ti bond: EtN{CH2[(2-Alk)(4-But)C6H2(2-O–)]}2Ti(O–But)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.