Coordination-insertion Mechanism Research Articles

Use of samarium(III)–amino acid complexes as initiators of ring-opening polymerization of cyclic esters

Poly(e-caprolactone) (PCL) and poly(l-lactide) (PLA) were prepared by ring-opening polymerization (ROP) using samarium(III) acetate (SmAc3) and amino acid complexes of samarium(III) as initiators. The catalytic behavior of samarium(III) acetate and their respective amino acid complexes, Sm(2,2′-bipyridine)(Ln)3 (L1 = l-aspartic acid; L2 = l-glutamic acid and L3 = glycine), was studied. It could be observed that the amino acid structure and chemical bond type have great influence on the catalytic activity. Polymerization reaction temperature was 125 °C and the effect of time reaction on the conversion of monomers to polymers and the molecular weight were studied. The results indicate that the initiators induce the polymerization of e-caprolactone (e-CL) and l-lactide (l-LA). Polymers were characterized by size exclusion chromatography (SEC) and nuclear magnetic resonance (1H-NMR) and size exclusion chromatography (SEC). Polyesters with average-number molar mass of 1.50 × 103 − 104 Da were obtained. Based on the 1H-NMR end group analysis of low molecular weight of polymers, a coordination–insertion mechanism is proposed for the polymerization of lactones. Kinetics study indicated a polymerization rate of first order with respect to monomer concentration. Differences in the rates of polymerization in the four initiators appeared to be governed by the different degrees of steric hindrance in the initiator structure and monomer.

Synthesis and characterization of trinuclear and mononuclear rare-earth metal aryloxides supported by Salpn ligand and their application for the polymerization of rac-lactide

Four rare-earth metal complexes supported by Salpn ligand were synthesized, and their catalytic behaviors for the polymerization of rac-lactide (rac-LA) were explored. The amine elimination reactions of Salpn ligand LH2 (LH2=(CH2)3[N=CH(C6H4-2-OH)]2) with RE[N(SiMe3)2]3 (RE=Y, Yb, Sm, Nd) in a 1:1M ratio, and then with 1 equiv. of phenol ArOH (ArO=2,6-But2-4-MeC6H2O) in THF gave the trinuclear rare-earth metal aryloxo complexes [LRE(OAr)(HMPA)]3 (RE=Y (1), Yb (2), Sm (3)), and the mononuclear neodymium complex LNd(OAr)(HMPA)2 (4), respectively, in good yields in the presence of HMPA (HMPA=hexamethylphosphoric triamide). Complexes 1 and 2 can also be prepared by the phenol elimination reactions of (ArO)3RE(THF) with LH2 in a 1:1M ratio or salt metathesis reaction of LLi2(THF)x with anhydrous RECl3, then with NaOAr in THF. Complexes 1–4 were well characterized by elemental analyses and IR, as well as NMR spectroscopy in the case of complex 1. The definitive molecular structures of complexes 1–4 were determined by single-crystal X-ray analysis. The catalytic behaviors of these complexes for rac-LA polymerization were investigated. It was found that complexes 1–4 can initiate efficiently this polymerization and gave hetero-rich PLA. Kinetics study demonstrated that rac-LA polymerization initiated by complexes 1–3 has a first order relationship between polymerization rate and monomer concentration. A comparative kinetics study in THF and CHCl3 revealed that polymerization media have significant influence on the activity order of complexes 1–3 for rac-LA polymerization. The observed activity-increasing order of these complexes in THF is in agreement with the increasing order of their ionic radii, whereas it is in reverse order in CHCl3. A mechanism study demonstrated that the polymerization proceeded via a coordination-insertion mechanism, and the aryloxo group in these complexes acted as the initiating group.

Aluminum Alkyl Complexes Bearing Salicylaldiminato Ligands: Versatile Initiators in the Ring-Opening Polymerization of Cyclic Esters

Linear aliphatic polyesters are degradable thermoplastic polymers, which can be obtained by ring-opening polymerization (ROP) of cyclic esters through a coordination-insertion mechanism. Aluminum based organometallic complexes have a leading position as efficient catalysts for this polymerization process. Aluminumalkyl complexes bearing salicylaldiminato ligands, although less explored, have been shown to be efficient and versatile catalysts for the ROP of various cyclic esters. These species have the potential to function as active catalysts in the ROP because of their less coordinatively saturated nature with respect to analogous SALEN-type complexes. They have been used as efficient catalysts in the ROP of commercially available cyclic esters, such as ε-caprolactone, l-lactide, rac-lactide, and glycolide. Moreover, they resulted in efficient catalysts for the ROP of cyclic esters with large ring-size and for the ROP of functionalized lactide. Furthermore, they have been used in the co- and ter-polymerization of various cyclic esters affording well controlled polymerization and a plethora of microstructural architectures, ranging from random to block to multiblock.

Synthesis of amine-bridged bis(phenolate) rare-earth metal aryloxides and their catalytic performances for the ring-opening polymerization of l-lactic acid O-carboxyanhydride and l-lactide.

A series of rare-earth metal complexes stabilized by different amine bridged bis(phenolate) ligands were synthesized and well characterized. Their catalytic performances for the ring-opening polymerization of l-lactic acid O-carboxyanhydride (l-lacOCA) and l-lactide were explored. Sequential reactions of amine bridged bis(phenol) with (C5H5)3RE(THF) in a 1 : 1 molar ratio, followed by 1 equivalent of p-cresol gave the amine bridged bis(phenolate) rare-earth metal aryloxides {La[NNOO-R](OC6H4-4-CH3)(THF)}2 {[NNOO-R] = Me2NCH2CH2N}{CH2-(2-O-C6H2-R2-3,5)}2, R = Me (1), La[NNOO-R](OC6H4-4-CH3)(THF)2 [R = tBu (2); R = Cumyl (3)], Y[NNOO-R](OC6H4-4-CH3)(THF) [R = tBu (4)] and {Y[THFONOO-tBu](OC6H4-4-CH3)}2 {THFONOO-tBu = (CH2)3OCHCH2N[CH2-(2-O-C6H2-3,5-tBu2)]2} (5) in good isolated yields. Single-crystal structure determination revealed that complexes 1 and 5 have dimeric structures, whereas complexes 2 and 3 have monomeric structures in the solid state. It was found that these complexes are efficient initiators for the ring-opening polymerization of l-lacOCA, and the overall coordination environments around the metal centers and the ionic radii of the metal centers have an obvious influence on the catalytic performance. A comparative study on the polymerization kinetics of l-lacOCA and l-lactide initiated by complex 5 was carried out for the first time. The results obtained demonstrated that the polymerization of l-lacOCA and l-lactide is first order for the catalyst and monomer concentration in dichloromethane, respectively, and the Gibbs energy of activation of l-lacOCA and l-lactide is found to be essentially the same. Mechanistic studies revealed that l-lacOCA polymerization initiated by these rare-earth metal complexes proceeded via a coordination-insertion mechanism.

Suppressing Cyclic Polymerization for Isoselective Synthesis of High-Molecular-Weight Linear Polylactide Catalyzed by Sodium/Potassium Sulfonamidate Complexes

A new sodium/potassium crown ether complex system with a series of bichelating sulfonamides as ligands was developed for the ring-opening polymerization (ROP) of rac-lactide. In this system, the side reaction of cyclic polymerization can be suppressed very well because of very different ROP rates initiated by BnOH and sulfonamide anion. The synthesis of high molecular weight linear polylactide with molecular weight high up to 107 kg/mol was successful. The best isoselectivity also can reach to a high value of Pm = 0.84. The NMR analysis of the reaction mixture of rac-lactide and complex 3 together with kinetic studies suggests the mechanism of ROP in the absence of alcohol is a coordination–insertion mechanism. After addition of BnOH, the ROP rate can increase remarkably due to the cooperation interaction of alcohol and complex 3.

Theoretical studies on aluminum trialkoxide-initiated lactone ring-opening polymerizations: Roles of alkoxide substituent and monomer ring structure

Four aluminum (III) trialkoxides, namely, Al(III) ethoxide (1), Al(III) isopropoxide (2), Al(III) tert-butoxide (3), and Al(III) sec.-butoxide (4), have been evaluated their efficiency as initiators for bulk ring-opening polymerizations (ROP) of some lactones (γ-butyrolactone (GBL), γ-valerolactone (GVL), δ-valerolactone (VL) and ε-caprolactone (CL)). The influences of the initiator’s alkoxide substituent and monomer ring structure on the initiating activity and mechanism of ROP were computationally analyzed by means of density functional theory (DFT) method. Upon the activation energies, the relative activities of the initiators toward CL ROP follow the trend 4>2>3>1, which were also confirmed by experiment. All initiators were found to follow the coordination-insertion mechanism. It was shown that 2 and 4 were efficient initiators for the reaction and the calculations demonstrate that their branch substituents play a key role in stabilizing intermediates and transition states that leads to lower reaction energies and activation barriers. The rate-determining step of the initiation was the formation of penta-O-coordinated Al, and their computed activation energies (24.5–34.8kcal/mol) were in agreement with available kinetic data.

Cadmium acetate as a ring opening polymerization catalyst for the polymerization of rac-lactide, ε-caprolactone and as a precatalyst for the polymerization of ethylene

In the present study, we have discussed the bulk ring opening polymerization (ROP) of rac-lactide (rac-LA) and e-caprolactone (e-CL) using Cd(OAc)2. Cd(OAc)2 appeared to be a good catalyst for the polymerization of rac-LA and e-CL yielding high molecular weight (Mn) polymers with narrow molecular weight distributions (MWDs). The catalytic activity of the system can be increased markedly upon using catalytic amount of BnOH as external alcoholic initiator. There is a first order dependence of the rate constant with respect to monomer concentrations as understood from the kinetic studies. The rate was found to be faster in the presence of BnOH. The polymerization process was controlled. The polymerization proceeded via the coordination-insertion mechanism without BnOH as well as activated monomer mechanism in the presence of BnOH. In the absence of BnOH, the acetyl group initiated the polymerization as understood from the 1H NMR and MALDI-TOF analysis. The benzyloxy group initiated the polymerization in the presence of BnOH. Moderate activity towards the polymerization of ethylene was observed using MAO as alkyl aluminum activator. The polymerization parameters towards the polymerization of ethylene were widely investigated.

Insertion Polymerization of Divinyl Formal

Copolymerization of ethylene and divinyl formal by [{κ2-P,O-(2-MeOC6H4)2PC6H4SO3}PdMe(dmso)] (1) by a coordination–insertion mechanism affords highly linear polyethylenes with a high (12.5 mol %) incorporation of divinyl formal. This significantly exceeds the thus far relatively low incorporation (6.9 mol %) and activity with vinyl ether monomer in insertion polymerization. The resulting ethylene–divinyl formal copolymers exclusively (>98%) contain five-membered (trans-1,3-dioxolane) and six-membered (cis-/trans-1,3-dioxane) cyclic acetal units in the main chain, and also in the initiating ends of this functionalized polyethylene. Comprehensive NMR analysis of the microstructure of these copolymers revealed that under pressure reactor conditions consecutive 2,1–1,2-insertion of divinyl formal into a Pd–H bond is preferred, but consecutive 1,2–1,2-insertion of divinyl formal into more bulky Pd–alkyls (growing polymer chain) is favored. Moreover, homopolymerization of divinyl formal yielded a non-cross-link...

Synthesis, characterization and l-lactide polymerization behavior of rare-earth metal bis(silylamide) complexes supported by arylamido ligand

Salt metathesis of LnCl3, [2,6-iPr2C6H3N(SiMe3)]Li and LiN(SiHMe2)2 in 1:1:2 molar ratio in THF produced the mono-arylamido-ligated rare-earth metal bis(silylamide) complexes [2,6-iPr2C6H3N(SiMe3)]Ln[N(SiHMe2)2]2(THF) (Ln = Y (1), Lu (2), La (3)) in good isolated yields. All these complexes were characterized by elemental analysis, NMR spectroscopy and FT-IR spectroscopy. 1 was further structurally authenticated by single crystal X-ray diffraction. These complexes alone could serve as highly active initiators for l-lactide polymerization in toluene at 50 °C. Employing 1 as the initiator, l-lactide polymerization proceeded in a controllable fashion via the coordination-insertion mechanism verified by end group analysis of the oligomer.

Structural and kinetic studies of the ring-opening polymerization of cyclic esters using N,N′ diarylformamidines Zn(II) complexes

The reactions of N,N′-bis(2,6-dimethylphenyl)formamidine (L1) and N,N′-bis(2,6-diisopropylphenyl)formamidine (L2), with Zn(OAc)2·2H2O salt and auxiliary benzoate ligands produced the respective Zn(II) formamidine benzoate complexes 1–4. All the complexes were characterized by IR, NMR spectroscopy elemental analysis and single crystal X-ray diffraction analyses for complexes 1, 2 and 3. Complexes 1–4 were active in the ring opening polymerization (ROP) of ɛ-caprolactone (ɛ-CL), d,l-lactide (d,l-LA) and l-lactide (l-LA) monomers. The kinetic results indicated a pseudo-first order dependency on the monomers. The nature of the N,N′ diarylformamidines ligands, auxiliary benzoate and solvent were found to affect the catalytic activity as well as the properties of the polymers. Activation parameters obtained from Eyring plots for the ROP of ɛ-CL using complex 4 points to coordination insertion mechanism.

DSC Kinetics Analysis for the Synthesis of Three‐Arms Poly(ε‐caprolactone) Using Aluminum Tri‐sec‐Butoxide as Initiator

ABSTRACTThe kinetics of the ring‐opening polymerization (ROP) of ε‐caprolactone (ε‐CL) initiated by soluble aluminum tri‐sec‐butoxide (Al(OsecBu)3) has been investigated by the differential scanning calorimetry (DSC). The DSC polymerizations were carried out under nonisothermal and isothermal conditions to obtain three‐arms poly(ε‐caprolactone) (PCL). From nonisothermal DSC, the polymerization rate (dα/dt) increased with increasing heating rates. The values of Ea were determined from Kissinger ( kJ mol−1), Friedman (31.0 – 63.0 kJ mol−1), and Starink (64.0 – 71.0 kJ mol−1) methods. From isothermal DSC, the dα/dt and the apparent rate constant (kapp) increased with increasing polymerization temperatures. The ROP of ε‐CL initiated by Al(OsecBu)3 occurred via the coordination insertion mechanism. The number average molecular weight () and percent yield of the synthesized PCL was enhanced by increasing polymerization temperature. The synthesized PCL with of 2.4 × 104 was obtained using a molar ratio of monomer to Al‐O active center ([M]/[Al‐O]) of 400 at 150ºC for 24 h. Al(OsecBu)3 is one of the promising initiator due to its solubility, low transesterification reaction, and high efficiency in ε‐CL polymerization.

Iron-catalyzed dehydropolymerization: a convenient route to poly(phosphinoboranes) with molecular-weight control.

The catalyst loading is the key to control the molecular weight of the polymer in the iron-catalyzed dehydropolymerization of phosphine-borane adducts. Studies showed that the reaction proceeds through a chain-growth coordination-insertion mechanism.

Ring-opening polymerization of lactides by (pyrazol-1-ylmethyl)pyridine Zn(II) and Cu(II) complexes: Kinetics, mechanism and tacticity studies

The kinetics, mechanism and polymer microstructure studies of ring-opening polymerization (ROP) of lactides (LA) by Zn(II) and Cu(II) complexes of (pyrazolylmethyl)pyridine ligands, 2-(3,5-dimethylpyrazol-1-ylmethyl)pyridine (L1) and 2-(3,5-diphenylpyrazol-1-ylmethyl)pyridine (L2) is described. The complexes [Zn(Ac)2(L1)] (1), [Cu(Ac)2(L1)] (2), [Zn(Ac)2(L2)] (3) and [Cu 2 (Ac) 4 (L2) 2 ]( 4) form active initiators in the ROP of D,L-LA and L-LA monomers. Generally Zn(II) complexes 1 and 3 exhibit higher activities compared to the corresponding Cu(II) complexes 2 and 4. Polymerization kinetics of D,L-LA show higher rates compared to the L-LA reactions. All the polymerization reactions follow pseudo first-order kinetics with respect to monomer while 1 shows second-order dependency on the polymerization reactions. Molecular weights of the polymers range from 813 g mol –1 to 9207 g mol –1 and exhibit relatively narrow molecular weight distributions between 1.2 to 1.6. While poly(D,L-LA) are predominantly atactic, poly(L-LA) are largely isotactic. All polymerization reactions proceed through coordination insertion mechanism followed by hydrolysis of the end groups.

Catalytic Activity of a Titanium(IV)/Iron(II) Heterometallic Alkoxide in the Ring-Opening Polymerization of ε-Caprolactone andrac-Lactide

The activity of the heterometallic alkoxide [FeCl{Ti2(OiPr)9}] (1) towards polymerization of rac-lactide (rac-LA) and e-caprolactone (e-CL) was investigated in toluene solution and in bulk at various temperatures, monomer/heterometallic alkoxide molar ratio and reaction times. The alkoxide 1 was active in solution for e-CL and in bulk for both monomers. Polymers were obtained in good yields with molecular weights ranging from 3890 to 15000 g moL-1 and polydispersity indexes (PDI) values varying from 1.3 to 2.5. Based on the 1H nuclear magnetic resonance (NMR) end-group analysis of polymers, a coordination-insertion mechanism was suggested for both monomers. The average number of growing chains per molecule of initiator (4 to 5 for rac-LA and 7 to 8 for e-CL) indicates that both bridging and terminal isopropoxides are active initiating groups. Kinetic studies with e-CL indicated that the polymerization rate is first order with respect to monomer concentration. The catalytic properties of 1 were compared to those found for other titanium(IV) and iron(II) complexes using e-CL as a model monomer.

Synthesis and Characterization of Amine-Bridged Bis(phenolate) Yttrium Guanidinates and Their Application in the Ring-Opening Polymerization of 1,4-Dioxan-2-one

A series of neutral yttrium guanidinates supported by an amine-bridged bis(phenolate) ligand were synthesized, and their catalytic behaviors for the ring-opening polymerization of 1,4-dioxan-2-one (p-dioxanone, PDO) were explored. Metathesis reactions of amine-bridged bis(phenolate) yttrium chlorides LLnCl(THF) [L = Me2NCH2CH2N{CH2-(2-OC6H2-tBu2-3,5)}2] with corresponding lithium guanidinates generated in situ in a 1:1 molar ratio in THF gave the neutral yttrium guanidinates LY[R2NC(NR1)2] [R1 = −Cy, R2N = −N(TMS)2 (1), −NiPr2 (2), −N(CH2)5 (3); R1 = −iPr, R2N = −NiPr2 (4) −NPh2 (5))]. These complexes were well characterized by elemental analyses, IR, and NMR spectroscopy. The definitive molecular structures of these complexes were determined by single-crystal X-ray analysis. It was found that these complexes can efficiently initiate the ring-opening polymerization (ROP) of PDO, and the catalytic activity is affected by the nature of the guanidinate groups with the active sequence of 1 > 2 ≈ 3 ≈ 4 > 5. The influences of reaction conditions such as polymerization time, polymerization temperature, and molar ratio of monomer to initiator on the polymerization were also investigated. The polymerization kinetics of PDO catalyzed by complex 1 is first-order with respect to monomer concentration, and the apparent activation energy amounts to 30.8 kJ mol–1. The mechanistic investigations showed that the ROP of PDO proceeded through a coordination–insertion mechanism with a rupture of the acyl–oxygen bond of the monomer. MALDI-TOF mass spectrum analysis of the oligomer revealed that there are two kinds of polymer chains in this catalytic system, e.g., the linear chains H–[OCH2CH2OCH2CO]n–OH and the PPDO macrocycles.

Effects of alkoxide alteration on the ring-opening polymerization of ε-caprolactone initiated by n-Bu3SnOR: a DFT study

The ring-opening polymerization (ROP) of e-caprolactone (CL) initiated by tributyltin alkoxides (n-Bu3SnOR), where R = methyl (Me), ethyl (Et), propyl (Pr), and butyl (Bu), was investigated using density functional theory at B3LYP level with mixed basis set. A coordination–insertion mechanism with two transition states was found for all ROP reactions: (1) starting with a coordination of CL onto Sn center led to a nucleophilic addition of the carbonyl group of CL, (2) followed by the exchange of alkoxide ligand with Sn atom and the ROP of CL was completed through classical acyl-oxygen bond cleavage. The barrier heights of all reactions with different initiators were calculated using potential energy profiles. All ROP reactions initiated with n-Bu3SnOR demonstrated exothermic reaction and the rate-determining step was the first transition state. The ROP of CL with n-Bu3SnOMe has the smallest value of barrier height compared to other reactions. Moreover, the activation energies for all ROP reactions, calculated using the transition state theory with TheRATE program, are in good agreement with available experimental data.

Carbene oligomerization promoted by nickelocene derived complexes

New catalytic systems based on nickelocene were used as initiators in polymerization of ethyl acetate carbene derived from ethyl diazoacetate. Nickelocene itself and nickelocene activated with n-butyllithium or diphenylmethyllithium led to the formation of oligomers with average molecular weight about 800Da. η5-Cyclopentadienyl(1,3-diallyl-imidazolin-2-ylidene)nickel bromide activated with an excess of methylalumoxane gave ethyl acetate carbene polymer with average molecular weight 21,800Da. MALDI TOF spectra indicate coordination–insertion mechanism of polymerization in all catalytic systems applied.

Theoretical study on the mechanism and kinetics of ring-opening polymerization of cyclic esters initiated by tin(II) n-butoxide

The coordination–insertion mechanisms of ring-opening polymerizations (ROP) of γ-valerolactone (GVL), δ-valerolactone (DVL) and l-lactide (LL) initiated by tin(II) n-butoxide were investigated using hybrid density functional theory at the B3LYP level with a mixed basis set. Analysis of geometries and corresponding energies revealed six intermediate states (including two transition states) observed in all three ROP reactions, which confirmed a coordination–insertion mechanism. Calculated energy profiles demonstrated exothermicity for each ROP reaction with a rate-determining step found for the first transition state that involved the attraction of an oxygen atom of the monomer to the metal atom of the initiator. By using the resulting energy barriers and transition state theory, the thermal rate constants could be obtained with the predicted rates of GVL and LL found to be equal and faster than that of DVL. In addition, by comparisons of the ring-strain energies and the barrier heights, we found that the effect of ring strain was at most only a partial driving force for the ROP reactions.

ɛ‐caprolactone and lactide polymerization promoted by an ionic titanium(IV)/iron(III) polynuclear halo‐alkoxide

ABSTRACTThe ionic [Ti3(µ3‐OPri)2(µ‐OPri)3(OPri)6][FeCl4] halo‐alkoxide (A) was investigated for its activity towards the bulk polymerization of rac‐lactide (rac‐LA) and ɛ‐caprolactone (ɛ‐CL) in various temperatures, monomer/A molar proportions, and reaction times. The reactivity of A in the ring‐opening polymerization (ROP) of both monomers is mainly due to the cationic [Ti3(OPri)11]+ unity and proceeds through the coordination–insertion mechanism. Molecular weights ranging from 6,379 to 13,950 g mol−1 and PDI values varying from 1.22 to 1.52 were obtained. Results of ROP kinetic studies for both ɛ‐CL and rac‐LA confirm that the reaction rates are first‐order with respect to monomers. The production of poly(ɛ‐caprolactone) shows a higher sensitivity of the reaction rate to temperature, while the polymerization of rac‐LA is slower and more dependent on the thermal stability of the active species during the propagation step. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 2509–2517

Dinuclear Zinc–N‐Heterocyclic Carbene Complexes for Either the Controlled Ring‐Opening Polymerization of Lactide or the Controlled Degradation of Polylactide Under Mild Conditions

AbstractWe describe the synthesis of the new Zn–N‐heterocyclic carbene (NHC) alkoxide complexes [(S,CNHC)ZnCl(OBn)]2 (5) and [(O,CNHC)ZnCl(OBn)]2 (6) for use as ring‐opening polymerization (ROP) initiators for lactide polymerization. Complexes 5 and 6 are readily available through an alcoholysis reaction between BnOH and the corresponding Zn–NHC ethyl species [(S,CNHC)ZnCl(Et)] (3) and [(O,CNHC)ZnCl(Et)] (4), and species 3 and 4 were obtained from the reaction of ZnEt2 with the N‐methyl‐N'‐ethylphenylsulfide (1⋅HCl) and N‐methyl‐N'‐ethylmethylether (2⋅HCl) imidazolium salts, respectively. Both solution and solid‐state structural data for Zn benzyloxide species 5 and 6 agree with dimeric structures under the studied conditions (reaction conditions: CH2Cl2 or THF, room temperature). A computational analysis of species 3 and 4 supports a dimeric structure in solution. The ZnII alkoxide species 5 and 6 were found to mediate either the ROP of lactide (in an effective and controlled manner) to produce chain length‐controlled polylactide (PLA) or, in the presence of an alcohol source such as MeOH, the controlled degradation of PLA through extensive transesterification reactions to afford methyl lactate as the major product. A thorough DFT computational analysis of the ROP of lactide initiated by complex 5 was performed, which revealed that the operating coordination–insertion mechanism was assisted by the second Zn center, leading to a lower‐energy ROP process; this result may be of interest for the future design of well‐defined and high‐performance metal‐based catalysts.