Undiscovered Potential: Ge Catalysts for Lactide Polymerization

Abstract

Polylactide (PLA) is a high potential bioplastic that can replace oil‐based plastics in a number of applications. To date, in spite of its known toxicity, a tin catalyst is used on industrial scale which should be replaced by a benign catalyst in the long run. Germanium is known to be unharmful while having similar properties as tin. Only few germylene catalysts are known so far and none has shown the potential for industrial application. We herein present Ge complexes in combination with zinc and copper, which show amazingly high polymerization activities for lactide in bulk at 150 °C. By systematical variation of the complex structure, proven by single‐crystal XRD and DFT calculations, structure–property relationships are found regarding the polymerization activity. Even in the presence of zinc and copper, germanium acts as the active site for polymerizing probably through the coordination–insertion mechanism to high molar mass polymers.

(N),C,N‐Coordinated Heavier Group 13–15 Compounds: Synthesis, Structure and Applications

“…The Ar CN *GeCl is also able to coordinate ZnCl 2 and CuX (X=Cl and I) to yield new heterobimetallic complexes {[Ar CN *(Cl)Ge]MX} 2 (M=ZnCl, Cu) (Scheme ) . The substitution reaction with K[BEt 3 H] provided {[Ar CN *(H)Ge]ZnCl 2 } 2 .…”

“…These complexes were tested as catalysts in the ring opening polymerization (ROP) of lactides (Scheme ). The polymerizations were done as solvent free experiments at 150 °C and complex {[Ar CN *(H)Ge]ZnCl 2 } 2 exhibited excellent activity with k p =3.806±0.315 L mol −1 s −1 which is much better than industrially used Sn(Oct) 2 with k p =(0.084±0.02) L mol −1 s −1 …”

N→Ge Coordinated Germylenes as Ligands for Monomeric Cu Complexes

“…Recently, we have shown that the reaction of the N!Ge coordinated germylene L(Cl)Ge (L = 2-Et 2 NCH 2 -4,6-tBu 2 -C 6 H 2 ) with CuCl or (CuI) 4 (SMe 2 ) 3 yielded the monomeric complexes [L(Cl)Ge] 2 CuX (X = Cl, I). [10] As substitution reactions of [L(Cl)Ge] 2 CuCl provided mixture of products and no selectivity was observed, here we present the reactivity of the [L(Cl)Ge] 2 CuI (1), where two L(Cl)Ge fragments coordinate monomeric CuI (Scheme 1). [10] The presence of two different halides in 1 allowed us to study its selective substitution reactions.…”

“…[10] As substitution reactions of [L(Cl)Ge] 2 CuCl provided mixture of products and no selectivity was observed, here we present the reactivity of the [L(Cl)Ge] 2 CuI (1), where two L(Cl)Ge fragments coordinate monomeric CuI (Scheme 1). [10] The presence of two different halides in 1 allowed us to study its selective substitution reactions.…”

Robust Guanidine Metal Catalysts for the Ring‐Opening Polymerization of Lactide under Industrially Relevant Conditions

“…With TOF values of up to 100000 h −1 the catalyst is classified as extremely active under industrial conditions. In addition to this development of zinc complexes for the ROP of technical grade lactide, a non‐toxic germanium complex ( 5 ) has recently been synthesized, which proved to be active in ring‐opening polymerization . Kinetic investigations showed that the germanium atom is the active center of the polymerization and that a CIM mechanism is proceeding.…”