Yttrium and aluminium complexes bearing dithiodiolate ligands: synthesis and application in cyclic ester polymerization

Yttrium and aluminium complexes of two dithiodiolate ligands that feature different bridges (CF3)(2)C(OH)CH2SRSCH2C(OH)(CF3)(2) (L-1-H-2, R = CH2CH2 and L-2-H-2, R = C6H4) were synthesized in good yields by reacting tris(silylamide)yttrium or trimethylaluminium with one equivalent of the proligand. All complexes were characterized by NMR and elemental analysis, and single-crystal X-ray structural analysis was also performed for one of the yttrium complexes. The catalytic activities of the four complexes in the ring-opening polymerization of epsilon-caprolactone and rac-lactide have been investigated. Furthermore, DOSY experiment and DFT calculations have been carried out to determine the structure of the isopropoxo derivative of the complex (LY)-Y-2 amide.