Investigation of redox switchable titanium and zirconium catalysts for the ring opening polymerization of cyclic esters and epoxides

Abstract

The synthesis and characterization of (thiolfan*)Zr(OtBu)2 (thiolfan* = 1,1′-di(2,4-di-tert-butyl-6-thiophenoxide)ferrocene) is reported, as well as its activity toward the ring-opening polymerizations of l-lactide and ε-caprolactone.

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.…”

Exploring Oxidation State-Dependent Selectivity in Polymerization of Cyclic Esters and Carbonates with Zinc(II) Complexes

“…However, in the case of the reduced species, a direct zinc-phosphine interaction was not observed. Despite this finding, and because of our interest in redox-switchable catalytic processes ( Abubekerov et al., 2016 , Abubekerov et al., 2017 , Wang et al., 2014 , Wang et al., 2015 , Quan and Diaconescu, 2015 , Brosmer and Diaconescu, 2015 , Abubekerov and Diaconescu, 2015 , Upton et al., 2014 , Broderick et al., 2011a , Broderick et al., 2011b , Broderick et al., 2011c , Quan et al., 2016 , Quan et al., 2017 , Lowe et al., 2017 , Shepard and Diaconescu, 2016 ), we set out to investigate the influence of the redox state of fc P,B on the zinc-mediated ring-opening polymerization of cyclic esters and carbonates. In addition, an investigation into the redox and polymerization activity of a monomeric ferrocene-chelating heteroscorpionate zinc complex, (fc P,B )Zn(OPh), is reported.…”

Use of pyrazoles as ligands greatly enhances the catalytic activity of titanium iso-propoxide for the ring-opening polymerization of l-lactide: a cooperation effect

“…Because of the non-cytotoxic property and strong Lewis acidity of titanium, Ti complexes 22,23,[30][31][32][33] are commonly used catalysts in LA ROP. Numerous Ti complexes bearing various ligands such as calix [4] arene, 33,34 Schiff base, [35][36][37][38][39] salen, [40][41][42] salan, [43][44][45][46] phenolate, [47][48][49][50] aminophenolate, 51,52 benzotriazole phenolate, [53][54][55] phosphinophenolate, 56 thiophenolate, 57,58 bis-phenolate-N-heterocyclic carbene, 45 pyridonate, 59,60 and pyrrolide 61 have been reported to exhibit considerable catalytic activity or controllability, which is contributed by ligands. However, for most studies, focusing on materials is inconvenient, because the synthesis and purication of Ti catalysts are time-consuming processes.…”