Versatile metal complexes of 2,5-bis{N-(2,6-di isopropylphenyl)iminomethyl}pyrrole for epoxide–CO2 coupling and ring opening polymerization of ε-caprolactone

Abstract

The catalytic activities of metal complexes of 2,5-bis{N-(2,6-diisopropylphenyl)iminomethyl}pyrrole 1 for epoxide-CO 2 coupling and ring opening polymerization (ROP) of 3-caprolactone (CL) were explored.The Zn(II) 2, Cd(II) 3,4 and Cu(II) 5 complexes of 1, in the presence of tetrabutylammonium bromide (TBAB) as co-catalyst, effectively catalyzed the epoxide-CO 2 coupling reaction at 1 atm of CO 2 to produce cyclic carbonates. In addition, the catalytic activities of these complexes (2-5) were investigated for the ROP of CL in the presence and absence of benzyl alcohol (BnOH). All these complexes were active for ROP of CL at mild temperature. In particular, the complexes 2 and 5 exhibited remarkable catalytic activities for ROP of CL at 25 C in toluene in the presence of BnOH. The ROP of CL catalyzed by 2 and 5 complexes, not only proceeded through living polymerization but also immortal.

Zn(ii) and Cu(ii) formamidine complexes: structural, kinetics and polymer tacticity studies in the ring-opening polymerization of ε-caprolactone and lactides

“…10) established the living polymerization behavior of these catalysts. 59,60 The observed increase in polymer weight with the increase in [CL]/[catalyst] ratio (low catalyst concentration) further supported this living polymerization nature (Table 3) and is consistent with a small number of active sites at lower concentration of the catalyst. Generally, the polymers obtained in this study exhibited narrow to moderate molecular weight distributions, 1.12-2.47 and 1.79-2.25 for PCLs and PLAs, respectively, indicating some degree of control of the ROP and minimal esterification and epimerization reactions.…”

Diiminopyrrolide Copper Complexes: Synthesis, Structures, and rac-Lactide Polymerization Activity

“…Babu et al reported (L diip ) 2 Cu­(MeOH) (L diip = 2,5-bis­(diisopropylphenylimino)­pyrrolide), which interestingly showed bidentate coordination of one and tridentate coordination of the other diiminopyrrolide ligand . Diiminopyrrolide complexes have not been used in lactide polymerization, but diiminopyrrolide yttrium and lanthanide complexes were active in the polymerization of ε-caprolactone. , We speculated that diiminopyrrolide ligands would be able to stabilize the open coordination site in a square-planar copper alkoxide complex, thus avoiding the decomposition reactions observed for copper diketiminates. In the presence of lactide monomer they would likely easily isomerize to bidentate coordination (Scheme ).…”

A unique cooperative catalytic system carrying metallic iron and 2-hydroxyethyl 2-bromoisobutyrate for the controlled/living ring-opening polymerization of ε-caprolactone

“…However, we have to admit that the catalytic activity of this polymerization system is lower than that using the Zn complex for the ROP of CL at 25 C (M n ¼ 11 956 g mol À1 , PDI ¼ 1.12, conversion ¼ 98%, 6 h). 24 The chain extension experiment also conrmed the controlled/living nature of the HEBiB/Fe-catalyzed ROP of CL. Fig.…”

“…All the listed hydroxyl initiators are suitable for the CL polymerization in this system, yielding the product with moderate to high yields depending on the nucleophilic character and steric feature of the hydroxyl initiator. 24…”

“…These polyesters have good hydrolyzability, mechanical properties, biocompatibility and miscibility with other polymers, making them leading candidates as drug delivery vehicles in the biomedical eld, scaffolds in tissue engineering, adhesives, microelectronics, and packaging. [1][2][3][4][5] Organometallic catalysts of Al, [6][7][8][9][10][11][12][13] Fe, [14][15][16][17] Zn, [18][19][20][21][22][23][24][25][26] Sn, [27][28][29] among several others, [30][31][32][33][34][35][36][37][38][39][40] have been used in these conversion processes. 2,3,[41][42][43] The difficulty of catalyst removal and the inherent toxicity associated with certain types of catalysts are the major barriers in the commercialization of PCLs and PLAs.…”