Isotactic rac‐Lactide Polymerization with Copper Complexes: The Influence of Complex Nuclearity

Abstract

Diiminopyrrolide copper alkoxide complexes, LCuOR (OR(1)=N,N-dimethylamino ethoxide, OR(2)=2-pyridyl methoxide), are active for the polymerization of rac-lactide at ambient temperature in benzene to yield polymers with M(w)/M(n)=1.0-1.2. X-ray diffraction studies showed bridged dinuclear complexes in the solid state for both complexes. While LCuOR(1) provided only atactic polylactide, LCuOR(2) produced partially isotactic polylactide (P(m)=0.7). The difference in stereocontrol is attributed to a dinuclear active species for LCuOR(2) in contrast to a mononuclear species for LCuOR(1).

Phosphasalen Indium Complexes Showing High Rates and Isoselectivities in rac‐Lactide Polymerizations

“…Zirconium/salalen catalysts showed P i =0.86, but are much slower than 1 . Diimino pyrrolide copper catalysts showed lower isoselectivity ( P i =0.70) and lower rates . The only comparable catalyst was reported very recently, and is an yttrium bis(phenolate) catalyst showing high rates ( k obs =4.25×10 −3 s −1 , toluene, 298 K, [LA]=2.5 m , [catalyst]=10 m m ) and isoselectivity ( P i =0.84 at 298 K; P i =0.90 at 258 K) .…”

Zn(II) and Cu(II) unsymmetrical formamidine complexes as effective initiators for ring‐opening polymerization of cyclic esters

“…Nevertheless, some tin compounds have appreciable cytotoxicity and are susceptible to atmospheric conditions which increase the production expenses . In this regard, research is now exploring the use of other organometallic compounds with lower toxicity such as alkali metals, magnesium, calcium, zinc, copper, iron, and aluminum all of which have shown promising results.…”

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

“…Multinuclear metal catalysts, such as yttrium, rare earths, group IV, iron, magnesium, copper, zinc, and aluminum have received enormous attention for ROP of cyclic esters. Tolman and co‐workers reported that the polymerization rate for LA with dinuclear zinc catalysts compares favourably to the fastest catalysts .…”