Aluminium complexes bearing functionalized trisamido ligands and their reactivity in the polymerization of ε-caprolactone and rac-lactide

The addition of 1 and 2 equivalents of AlMe(3) to cis,cis-C(6)H(9)(NHCH(2)C(6)H(4)-o-R)(3) (R = PPh(2) (3) and SPh (4)) gives complexes [cis,cis-C(6)H(9)(NCH(2)C(6)H(4)-o-R-kappaN)(2)(NHCH(2)C(6)H(4)-o-R-kappaN)]AlMe (R = PPh(2) (7) and SPh (8)) and [cis,cis-C(6)H(9)(NCH(2)C(6)H(4)-o-R)(3)-kappa(5)mu(2)N]Al(2)Me(3) (R = PPh(2) (5) and SPh (6)), respectively. The bimetallic complexes are active in the polymerization of epsilon-caprolactone and rac-lactide whereas the monometallic complexes are not, although no cooperative behaviour is observed between the two aluminium atoms of 5 and 6. The polycaprolactone samples, which were characterized using (1)H NMR, MALDI-TOF, and SEC, show the presence of residual ligands 3 or 4 bound to the polymer and the in situ NMR studies confirm that the insertion occurs in an Al-N bond.