Synthesis, characterization and catalytic activity of magnesium and zinc aminophenoxide complexes: Catalysts for ring-opening polymerization of l-lactide

Abstract

A series of novel magnesium and zinc aminophenoxide complexes were successfully synthesized and one zinc complex was characterized by X-ray crystallography. They were also investigated as initiators for the ring opening polymerization of L-lactide. The complexes are effective in forming polylactides with good conversions. The nature and steric bulk of the ligands coordinated to the central metal ions enormously influenced the polymer properties. Among all the complexes, the zinc aminophenoxide complexes as initiators produced polymers with good molecular weight control and relatively narrow PDIs.

Dual zinc catalysts for L‐lactide polymerization and reaction of CO2 with cyclohexene oxide

“…For instance, LA conversion is only 7% within 45 second when a mixture of BnOH and L ‐LA was added to L 4‐OMe ZnEt ( 3 ) (entry 11 in Table ), and the conversion reached 92% after 3 hr (entry 12, Mn NMR = 4,500, Mn GPC = 7,200, Đ = 1.19), and it implied that the mixing ethyl Zn complexes and BnOH for 1 hr beforehand was very important. This may be ascribed to the fact that alkyl Zn complexes could react with benzyl alcohol forming active Zn alkoxide complexes as reported in the literature . To understand the real mechanism, the 1 H NMR study of the mixture of LA, L diBu ZnEt (5) , and BnOH (4:1:2) in benzene‐d 6 and toluene (2:1) cosolvent was investigated as shown in Figure S1.…”

DFT calculations as a ligand toolbox for the synthesis of active initiators for ROP of cyclic esters

“…The well-defined aminophenolate zinc complexes with a single-site motif determined by X-ray analysis are limited to merely a few examples. 29,37,38,40 All of them possess a di-tert-butyl phenol core in the ancillary ligands, and their coordination properties are controlled by backbone variations on nitrogen atoms. The modification of the aryl core or amine substituents with sterically bulky groups has been routinely used to restrict the aggregation of metal aryloxides formed during an alcoholysis.…”

“…The distances and angles are all comparable with bond lengths and angles observed for similar complexes described in the literature. 37,38,43,44 The geometric parameters for (L ox ZnEt) 2 obtained by DFT calculations were compared with the experimental data ( Table 1). The agreement between the optimized geometric structure and the experimental data from the X-ray analysis is fully satisfactory, and the only essential difference may be the position of the ethyl group bonding to the zinc centres ( Fig.…”

“…Excellent initiators have been obtained using biometals coordinated by numerous ancillary ligands such as β-diketiminate, [20][21][22][23][24] tris(pirazolyl)borate, [25][26][27][28][29] and related N,O-donor ligands. [29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45] However, most of them have been generated by in situ alcoholysis of alkyl LMR/(LMR) 2 compounds.…”

Preparation and Characterization of Self-Assembled Poly(l-Lactide) on the Surface of β-Tricalcium Diphosphate(V) for Bone Tissue Theranostics

“…The most effective and controlled method for PLA synthesis is metal-catalyzed/-initiated ring-opening polymerization (ROP) of lactide [12][13][14]. Among the wide variety of catalytic systems, the most attractive so far are the single-site initiators based on structural motif L-M-OR, where L is the ancillary ligand, M is the metal center, and OR is the initiating group [15][16][17][18][19][20][21][22][23]. Alternative, similarly attractive in the controlled synthesis of PLA are binary catalytic systems based on the homoleptic complexes and external alcohol combination [24][25][26].…”