Investigation of a zirconium compound for redox switchable ring opening polymerization

Abstract

Redox switchable catalysis with a ferrocene Schiff base zirconium complex allowed the synthesis of diblock and triblock copolymers.

Cooperative Effects in Multimetallic Complexes Applied in Catalysis

“…Further investigations into this research area led to the development of a series of symmetrically substituted tetradentate 1,1'-ferrocene ligands that incorporate early transition or group 13 metals (Figure 15). [136,[137][138][139][140] While detailed examinations of these catalysts have already been summarized in another review, [114] in regards to cooperativity it should be noted that oxidation generally influences the reactivity of the catalyst. An interesting example for this is the usage of a Y(III) and an In(III) catalyst, which bear the same ligand in polymerization of trimethylene carbonate.…”

“…[141] A remarkable achievement is the usage of redox-active polymerization catalysts to generate triblock polymers by means of switching the catalyst in situ multiple times (Scheme 44). [138][139][140] Oxidation of the complex leads to a change in selectivity towards the monomers, essentially switching off the activity for one substrate, while switching it on for another.…”

Switchable Ring‐Opening Polymerization by a Ferrocene Supported Aluminum Complex

“…It is unusual for metal complexes to be able to ring open TMC in the presence of LA, due to a strong 5‐membered ring metal lactide‐coordination‐insertion intermediate, but we attempted to study this reaction further given the success in synthesizing the (PTMC/PLA)‐PCHO‐PLA‐O i Pr block copolymer. First, LA was polymerized to a near full completion, which required heating for 4 days at 100 °C (Table , entry 6).…”

“…The aluminum analogue, (thiolfan*)Al(O t Bu), was not very selective between the two oxidation states, but could be used to synthesize various AB type diblocks with and without employing redox switching. Related supported ligands could also be used with zirconium as redox switchable catalysts: (salfan)Zr(O t Bu) 2 (salfan=1,1′‐di(2‐ tert ‐butyl‐6‐ N ‐methylmethylenephenoxy)ferrocene, Figure b) had the capability to synthesize an ABC type triblock of PBL‐PCHO‐PLA‐O t Bu, while (salfen)Zr(O i Pr) 2 (salfen=1,1′‐di(2,4‐bis‐ tert ‐butyl‐salicylimino)ferrocene, Figure c) could synthesize an ABA type PLA‐PCHO‐PLA triblock via two redox switches. When the indium analogue, (salfen)In(O t Bu) (Figure d), was examined, a high ring‐opening polymerization activity toward several lactones was observed with the reduced compound, but the catalyst was not redox switchable.…”

Synthesis of Biodegradable Polymers: A Review on the Use of Schiff-Base Metal Complexes as Catalysts for the Ring Opening Polymerization (ROP) of Cyclic Esters

“…Similarly, the reaction rate as well as the heterotactic bias increased with the steric bulk of the ligand. Finally, a redox-switchable Salfen Zr species has been successfully employed in the synthesis of bi-and triblock copolymers of L-LA and cyclohexene oxide [46].…”