0000000000436072
AUTHOR
Norikazu Ueyama
Titanium complexes having chelating diaryloxo ligands bridged by tellurium and their catalytic behavior in the polymerization of ethylene
A series of titanium complexes having tellurium-bridged chelating bis(aryloxo) ligands, [TiX2{2,2‘-Te(4-R-6-R‘-C6H2O)2}]2 (5b, X = Cl, R = Me, R‘ = tBu; 6a, X = OiPr, R = R‘ = H; 6b, X = OiPr, R = Me, R‘ = tBu), were prepared. 5b and 6b were determined by X-ray crystallography to have chloro- and isopropoxo-bridged dimeric structures. The structural data for these complexes indicated that the Ti−Te coordination bonds were stronger than the similar Ti−S coordination bonds in the corresponding sulfur-bridged complexes. The reaction of (C5R5)TiCl3 (R = H, Me) with 2,2‘-Te(4-R-6-R‘-C6H2OLi)2 gave monocyclopentadienyl derivatives, (C5R5)TiCl{2,2‘-Te(4-Me-6-tBu-C6H2O)2} (7, R = H; 8, R = Me). The…
Polymerizations of Cyclic Esters Catalyzed by Titanium Complexes Having Chalcogen-Bridged Chelating Diaryloxo Ligands
A series of titanium complexes having tellurium-bridged chelating bis(aryloxo) ligands, [TiX2{2,2‘-Te(4-Me-6-tBu-C6H2O)2}]2 (5: X = Cl; 6: X = OiPr), catalyzed the ring-opening polymerization of cyclic esters such as e-caprolactone, δ-valerolactone, and l-lactide. The strong dependence of polymerizations on the solvent was observed in this catalytic system. When the polymerizations of e-caprolactone and l-lactide were carried out in toluene at 100 °C, tellurium-bridged bis(aryloxo)titanium complex 5 was found to give polymers with rather broad molecular weight distribution due to back-biting. When the polymerizations of e-caprolactone and l-lactide was carried out in anisole or in dioxane…