New Racemic and Single Enantiopure Hybrid Scorpionate/Cyclopentadienyl Magnesium and Zinc Initiators for the Stereoselective ROP of Lactides

Abstract

The preparation of the first racemic bis(pyrazol-1-yl)methane-based NNCp-donor hybrid scorpionate/cyclopentadienyl magnesium and zinc complexes [Mg(R)(κ 2 -η 5 -NNCp)] (1−6) [NNCp = bpztcp, R = Me (1), Et (2), CH 2 SiMe 3 (3); bpzpcp, R = Me (4), Et (5), CH 2 SiMe 3 (6)] and [Zn(R)(κ 2 -η 1 -NNCp)] (7−12) [NNCp = bpztcp, R = Me (7), Et (8), CH 2 SiMe 3 (9); bpzpcp, R = Me (10)

Cubane‐Type Polynuclear Zinc Complexes Containing Tridentate Schiff Base Ligands: Synthesis, Characterization, and Ring‐Opening Polymerization Studies of rac‐Lactide and ε‐Caprolactone

“…ROP processes offer excel control in terms of molecular weight ( M n ), polydispersity (MWDs) and microstructure . Several complexes have been successfully employed in the ROP of lactide, including lithium, sodium, potassium, magnesium, calcium, strontium, aluminum, tin, zinc, some transition metals, and rare‐earth metals . Since complete elimination of catalyst rests from the polymer is virtually impossible, it is highly preferable to use non‐ or low toxic metals (for instance for biomedical applications).…”

Zinc Complexes of Sequential Tetradentate Monoanionic Ligands in the Isoselective Polymerization of rac‐Lactide

“…[11] Although af ew of these catalysts exhibited high activities, they have traditionally tended to be either non-stereoselective or heteroselective, [12] ando nly recently have several reports appeared describing isoselective polymerization of rac-LA. [13] One remarkable zinc catalyst was introduced by Hillmyer,T olman and co-workers in 2003 ( Figure 1). [14] The precatalyst wasa ne thylzinc unit bound to at ridentate monoanionic diamine-monophenolate {ONN} ligand.T he addition of ethyl alcoholl ed to ac atalystt hat exhibitedv ery high activity,c onsuming 500 equivalents of rac-LA in 5min at RT.H owever, the PLA obtained was atactic.…”

Synthesis and Application of Bimetallic Zinc(II) Phenoxy-Imine Complexes as Initiators for Production of Lactide Polymers

“…L1 and L2 were synthesized in high yields according to a modified literature procedure. [14][15][16][17]22 Complexes C1 and C2 ( Figure 1) were also obtained in high yields. The structures of these ligands allow the coordination of two zinc(II) centers while the vast majority of the phenoxy-imine ligands coordinate to only one metal.…”

“…Yield: 62%; mp > 300 °C; elemental analysis for C 24 C1 was prepared using a modified literature procedure. [14][15][16][17] In a 25 mL Schlenk flask, 15% hexane solution of ZnEt 2 (0.20 mL, 0.22 mmol) was added dropwise to a solution of L1 (0.100 g, 0.11 mmol) in dry toluene (10 mL) at 0-4 °C (L1/ZnEt 2 molar ratio = 1:2). The reaction mixture was stirred overnight at room temperature.…”