Ligand Variations in New Sulfonamide-Supported Group 4 Ring-Opening Polymerization Catalysts

The synthesis, structures, and ring-opening polymerization (ROP) capability of a wide range of sulfonamide-supported group 4 amide, alkyl, and alkoxide complexes, varying in sulfonamide N-substituent, metal, coordination number, and geometry, are reported. Reaction of Ti(NMe2)(4) or Ti(NMe2)(2)((OPr)-Pr-i)(2) with MeOCH2CH2N(CH2CH2NHSO2Me)(2) (12, (H2N2NOMe)-N-Ms) or PhCH2N(CH2CH2NHSO2R)(2) (R = Tol (10, (H2N2NPh)-N-Ts) or Me (11, (H2N2NPh)-N-Ms)) afforded Ti((N2NOMe)-N-Ms) (NMe2)(2) (18), Ti((N2NPh)-N-Ts)(NMe2)(2) (19), Ti((N2NPh)-N-Ms)(NMe2)(2) (20), Ti((N2NOMe)-N-Ms)((OPr)-Pr-i)(2) (21), Ti((N2NPh)-N-Ts)((OPr)-Pr-i)(2) (22), Ti((N2NPh)-N-Ms)((OPr)-Pr-i)(2) (23), and Ti((N2NPh)-N-Ts)((OPr)-Pr-i)(NMe2) (24). Reaction of N(CH2CH2NHSO2R)(3) (R = Tol (13, (H3N3N)-N-Ts), Me (14, (H3N3N)-N-Ms), or Ar-F (15, (H3N3N)-N-ArF, Ar-F = 3,5-C6H3(CF3)(2))) with Zr(CH2SiMe3)(4) formed Zr((N3N)-N-R)(CH2SiMe3) (R = Ts (30), Ms (31), or Ar-F (32)). Reaction of 15 with Zr(NMe2)(4) gave Zr((N3N)-N-ArF)(NMe2) (33). Complexes 19, 21, 24, 30, 32, and 33 were crystallographically characterized. Monomeric six- or five-coordinate structures were found for the titanium complexes 19, 21, and 24, whereas the zirconium alkyls 30 and 32 were dimeric in the solid state with terminal and bridging.kappa(2)(N,O)-bound sulfonamides. Complexes 18-24 and 30-33, the previously reported Ti(CyN2R)((OPr)-Pr-i)(2) (25 or 26; CyN2R.= 1,2-C6H10(NSO(2)Tol)(2) or 1,2-C6H10(NSO(2)Mes)(2)), and in situ generated isopropoxide initiators derived from 30-32 were investigated for the ROP of epsilon-caprolactone (epsilon-CL). The four-coordinate 25 was the most active, forming poly(epsilon-CL) with a relatively narrow PD1 and well-controlled M-n. Compounds 22, 23, 25, and 26 and isopropoxides generated in situ from 30-32 were all active for the ROP of rac-lactide. Of these, the initiators based on Zr((N3N)-N-R)(CH2SiMe3) (30-32) with (PrOH)-Pr-i co-initiator gave good activities and excellent PDIs (1.08-1.11) and agreement between measured and predicted M-n.