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

The addition of 1 and 2 equivalents of AlMe3 to cis,cis-C6H9(NHCH2C6H4-o-R)3 (R = PPh2 (3) and SPh (4)) gives complexes [cis,cis-C6H9(NCH2C6H4-o-R-κN)2(NHCH2C6H4-o-R-κN)]AlMe (R = PPh2 (7) and SPh (8)) and [cis,cis-C6H9(NCH2C6H4-o-R)3-κ5μ2N]Al2Me3 (R = PPh2 (5) and SPh (6)), respectively. The bimetallic complexes are active in the polymerization of ε-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 1H 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