YTTRIUM(III) PINCER COMPLEXES AS CATALYSTS IN RING-OPENING POLYMERIZATION OF epsilon-CAPROLACTONE

Reaction of YCl3 with Li[N(SiMe3)(2)] in a mixture toluene-tetrahydrofurane gives the complex YCl2 [N(SiMe3)(2)] (THF)(3) (1). This complex reacts with the tridentate ligands 2,6-bis(3,5-dimethylpyrazol-1-ylmethyl) pyridine and 2,6-bis(indazol-2-ylmethyl) pyridine to yield pincer complexes of general formula YCl2 [N(SiMe3)(2)] {2,6-bis(azolylmethyl) pyridine-N, N, N}(2,3). The yttrium(III) complexes were synthesized at NMR scale and characterized by NMR spectroscopy (H-1, C-13, Si-29). The complexes behave as highly active catalysts in the polymerization of epsilon-caprolactone at room temperature. The polymers were characterized by means of IR and NMR spectroscopy, and SEC (Size Exclusion Chromatography).