Sulfonamide-Supported Group 4 Catalysts for the Ring-Opening Polymerization of ε-Caprolactone and rac-Lactide

Reaction of RCH2N(CH(2)CH(2)NHSO(2)Tol)(2) (R=2-NC5H4 (8,H2Lpy) or MeOCH2 (9, H2LOme)) with Ti(NMe2)(4) at room temperature afforded Ti(L-py)(NMe2)(2) (10) or Ti(L-OMe) (NMe2)(2) (11), respectively, which contain tetradentate bis(sulfonamide)amine ligands. The corresponding reactions With Ti((OPr)-Pr-i)(4) or Zr((OPr)-Pr-i)(4). (HOPr)-Pr-i required more forcing conditions to form the homologous bis(isopropoxide) analogues, M(L-R)((OPr)-Pr-i)(2) (M=Ti R=py (12) or OMe (14); M=Zr, R=py (13) or OMe (15)). Reaction of Ti(NMe2)(2)((OPr)-Pr-i)(2) with H2LR formed 12 or 14 under milder conditions. The X-ray structures of 10-15 have been determined revealing C-s symmetric, 6-coordinate complexes except for 13 which is 7-coordinate with one kappa(2)(N,O) bound sulfonamide donor. Compounds 10- 15 are all catalysts for the ring-opening polymerization (ROP) of epsilon-caprolactone, with the isopropoxide compounds being the fastest and best controlled, especially in the case of zirconium. In addition, Zr(L-OMe)((OPr)-Pr-i)(2) (15) was an efficient catalyst for the well-controlled ROP of rac-lactide both in toluene at 100 degrees C and in the melt at 130 degrees C, giving atactic poly(rac-lactide). The polymerization rates and control achieved for 13 and 15 are comparable to those of the well-established bis(phenolate)amine-supported Group 4 systems reported recently.