Ring-opening polymerization of lactide using chiral salen aluminum complexes as initiators: high productivity and stereoselectivity

Abstract

Chiral salen aluminum complexes have been synthesized and investigated as initiators for l-lactide and rac-lactide polymerization.

Simple Zn(ii) complexes for the production and degradation of polyesters

“…However, the stereoselective ROP of rac-lactide can improve the material properties of the polymer and thus it is oen studied in academic research. A diverse range of metals has been applied to lactide ROP including Mg(II), 15,16 group IV, [17][18][19][20][21][22][23][24] Fe(II/III), [25][26][27][28][29][30][31][32] Al(III), [33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49] and In(III). [50][51][52] Initiators based on zinc(II) have consistently shown high activity under solvent-free conditions and, in some cases, stereocontrol is observed.…”

Tuning the Thiolen: Al(III) and Fe(III) Thiolen Complexes for the Isoselective ROP of rac-Lactide

“…There are examples of initiators based on Lewis acidic metals that produce isotactic PLA. These include: Na(I)/K(I), [9][10][11][12] Mg(II), 13,14 Ti(IV), 15 Zr(IV)/Hf(IV), [16][17][18][19][20][21][22] Zn(II), [23][24][25][26][27][28][29][30] Y(III), [31][32][33][34][35] Al(III) [36][37][38][39][40][41][42][43][44][45][46][47][48][49] and In(III). [50][51][52][53] The exact reasons why certain ligand-metal combinations offer high selectivity is still a matter of great academic and industrial interest.…”

“…There are examples of initiators based on Lewis acidic metals that produce isotactic PLA. These include: Na­(I)/K­(I), − Mg­(II), , Ti­(IV), Zr­(IV)/Hf­(IV), − Zn­(II), − Y­(III), − Al­(III), − and In­(III). − The exact reasons why certain ligand–metal combinations offer high selectivity is still a matter of great academic and industrial interest …”

Enhanced Reactivity of Aluminum Complexes Containing P-Bridged Biphenolate Ligands in Ring-Opening Polymerization Catalysis

“…These complexes are intriguing as their catalytic activities are finely tunable by judiciously varying the peripheral substituents on the two phenolate rings and/or the bridge in between. While most studies concentrate on metal complexes of tetradentate biphenolate ligands such as ONNO (Ovitt and Coates, 2000; Zhong et al, 2002; Hormnirun et al, 2006; Zelikoff et al, 2009; Chen et al, 2012; Gao et al, 2015; Jones et al, 2015; Kirk et al, 2016; MacDonald et al, 2016; McKeown et al, 2016; Robert et al, 2017; Pang et al, 2018), OSSO (Buffet and Okuda, 2011; Buffet et al, 2011), ONSO (Stopper et al, 2012), and ONOX (X = OR, NR 2 ) (Alcazar-Roman et al, 2003; Gendler et al, 2006; Tang and Gibson, 2007; Phomphrai et al, 2010; Wichmann et al, 2012) as exemplified in Figure 1, parallel research centered upon tridentate counterparts is relatively rare (Chmura et al, 2006; Chang and Liang, 2007; Hsu and Liang, 2010; Liang et al, 2011, 2013a,b,c,d,e; Huang et al, 2013; Klitzke et al, 2014a,b; Chang et al, 2016).…”