–ONNO–四齿配体负载铜(Ⅱ)配合物的合成与结构研究:环二酯开环聚合的高效催化剂(英文)

The –ONNO– tetradentate Schiff base ligand N,N'-bis(2-hydroxy-3- methoxybenzaldehyde) benzene-1,2-diamine(HMBBD) has been synthesized. The ligand was attached to copper(Cu-HMBBD) in methanol under N_2 atmosphere to give a mononuclear complex. The reactivity of this complex in the ring-opening polymerization(ROP) of lactide has been studied. The complex has a square planner geometry, as determined by X-ray diffraction studies. The copper complex is highly active towards the ring-opening polymerization of lactide, and the rate of polymerization is heavily dependent on the initiator used. The copper complex allows controlled ring-opening polymerization, as shown by the linear relationship between the percentage conversion and the number average molecular weight. Based on the literature, a mechanism for the ROP of lactide has been proposed.     

Polymerization of lactide and synthesis of block copolymer catalyzed by copper(Ⅱ) Schiff base complex

In the present investigation, the novel copper Schiff base complex was synthesized and its catalytic activity was evaluated for the ring-opening polymerization (ROP) of lactide and block polymerization of poly(lactide) with poly(ethylene glycol)methyl ether.     

Thermodynamic and Kinetic Polymerizability of Cyclic Esters

Recent advances in the controlled ring-opening polymerization (ROP) of cyclic aliphatic esters are reviewed with a particular attention to thermodynamics and kinetics of the polymerization of industrially important monomers, namely: lactide (LA), 1,4-dioxan-2-one (DX), and ϵ-caprolactone (CL). For comparison, polymerization of β-lactones is discussed. Progress in stereocontrolled polymerization of monomers bearing centers of chirality [LA and β-butyrolactone (BL)] is also briefly reviewed.     

Alkaline Earth Metal‐Mediated Highly Iso‐selective Ring‐Opening Polymerization of rac‐Lactide

Alkaline earth (Ae) metal complexes of the aminophosphine borane ligand are highly active and iso‐selective catalysts for the ring‐opening polymerization (ROP) of rac‐lactide (LA). The polymerization reactions are well controlled and produce polylactides with molecular weights that are precise and narrowly distributed. Kinetic studies reveal that the ROP of rac‐LA catalyzed by all Ae metal complexes had a first‐order dependency on LA concentration as well as catalyst concentration. A plausible reaction mechanism for Ae metal complex‐mediated ROP of rac‐LA is discussed, based on controlled kinetic experiments and molecular chain mobility.     

A computational insight into a metal mediated pathway for the ring-opening polymerization (ROP) of lactides by an ionic {(NHC)2Ag}(+)X(-) (X = halide) type N-heterocyclic carbene (NHC) complex

A metal mediated coordination-insertion pathway for the ring-opening polymerization (ROP) of L-lactide by an ionic {(NHC)(2)Ag}(+)X(-) (X = halide) type silver complex of N-heterocyclic carbene (NHC) has been investigated using the density functional theory (DFT) method. A clear insight into the lactide insertion process could be obtained by modeling two consecutive monomer addition steps with the first one mimicking chain initiation with the second representing a propagation step. In particular, in each of the cycles, the reaction initiates with the formation of a lactide coordinated species, [1+LL] and [2+LL] that transforms into a metal bound cyclic lactide intermediate, I([1+LL]→2) and I([2+LL]→3), which subsequently ring opens to give the lactide inserted products, 2 and 3. The estimated overall activation barrier for the initiation step is 42.0 kcal mol(-1) while the same for the propagation step is 31.5 kcal mol(-1). Studies on higher monomer insertions showed a decrease in the relative product energies as anticipated for an addition polymerization pathway.     

Mechanism of living lactide polymerization by dinuclear indium catalysts and its impact on isoselectivity

A family of racemic and enantiopure indium complexes 1-11 bearing bulky chiral diaminoaryloxy ligands, H(NNO(R)), were synthesized and fully characterized. Investigation of both the mono- and the bis-alkoxy-bridged complexes [(NNO(R))InX](2)[μ-Y][μ-OEt] (5, R = (t)Bu, X = Y = Cl; 8, R = Me, X = I, Y = OEt) by variable temperature, 2D NOESY, and PGSE NMR spectroscopy confirmed dinuclear structures in solution analogous to those obtained by single-crystal X-ray crystallography. The dinuclear complexes in the family were highly active catalysts for the ring-opening polymerization (ROP) of lactide (LA) to form poly(lactic acid) (PLA) at room temperature. In particular, complex 5 showed living polymerization behavior over a large molecular weight range. A detailed investigation of catalyst stereoselectivity showed that, although (R,R/R,R)-5 is highly selective for l-LA, only atactic PLA is obtained in the polymerization of racemic LA. No such selectivity was observed for complex 8. Importantly, the selectivities obtained for the ROP of racemic LA with (R,R/R,R)-5 and (R,R/R,R)-8 are different and, along with kinetics investigations, suggest a dinuclear propagating species for these complexes.     

Synthesis, characterization of neodymium chloride complex of amine-bis(phenolate) ligand and its reactivity in the ring-opening polymerization of ε-caprolactone

The neodymium chloride complex[Nd（ONN’O）Cl（THF）]₂ supported by amine-bis（phenolate） ligand was synthesized by the metathesis reaction of anhydrous NdCl₃ with Li₂（ONN’O）[H₂ONN’O = Me₂NCH₂CH₂N（CH₂-3-Bu₂^t-5-Me-C₆H₂OH）₂]in high yield.X-ray structural determination shows[Nd（ONN’O）Cl（THF）]₂ complex consists of two seven-coordinate neodymium centers linked throughμ-Cl bridges.And this complex was successfully used to initiate the ring-opening polymerization（ROP） ofε-caprolactone.     

Rare-earth metal complexes supported by 1,omega-dithiaalkanediyl-bridged bis(phenolato) ligands: synthesis, structure, and heteroselective ring-opening polymerization of rac-lactide

Monomeric yttrium and lutetium bis(phenolato) complexes [Ln(OSSO){N(SiHMe 2) 2}(THF)] (Ln = Y, Lu) were prepared from the reaction of silylamido complexes [Ln{N(SiHMe 2) 2} 3(THF) 2] with 1 equiv of tetradentate 1,omega-dithiaalkanediyl-bridged bis(phenol) (OSSO)H 2 1- 9 in moderate to high yields. In contrast to the rigid configuration of scandium analogues, the yttrium complexes 2b and 3b and the lutetium complex 3c that contain a C 2 bridge between the two sulfur donors of the ligand are symmetric in solution. The monomeric nature of these complexes was indicated by an X-ray diffraction study of the yttrium complex 6b. The yttrium center in 6b is coordinated to the tetradentate [OSSO]-type ligand, one silylamido group and one THF ligand with the two oxygen donors of the [OSSO]-type ligand located trans. Corresponding bis(phenolato) silylamido complexes of larger rare-earth metals could not be obtained from similar reactions: Reaction of [La{N(SiHMe 2) 2} 3(THF) 2] with 1,2-xylylene-linked bis(phenol) gave a dinuclear lanthanum complex 6d of the formula [La 2(OSSO) 3] with two inequivalent eight-coordinate metal centers. The yttrium and lutetium complexes efficiently initiated the ring-opening polymerization (ROP) of lactides in THF. The heteroselectivity during the ROP of rac-lactide was enhanced when the steric demand of the bis(phenolato) ligand was increased, either by extending the bridge length or by introducing bulky ortho-substituents in the phenoxy units. A C 3 bridge within the ligand backbone is essential to allow configurational interconversion of the active site between Lambda and Delta configuration during polymerization, allowing accommodation of both enantiomers of the monomer in an alternating fashion.     

Investigation of the synthesis of poly-D,L-lactide-co-poly(ethylene glycol) flexible thermoplastic

A series of biodegradable poly(D,L-lactide)-poly(ethylene glycol) multiblock poly(ether-ester-urethane)s with various lactide-to-poly(ethylene glycol) (LA/PEG) mole ratios has been successfully synthesized by ring-opening polymerization (ROP) followed by chain extension reaction through formation of urethane linkage. Resulting FT-IR spectra indicate complete polymerization of lactide monomers, while NMR analysis quantitatively marks the chain length of polymer blocks. The molecular weight and dispersion index of copolymers were investigated by GPC analysis. DSC thermogram and XRD diffractogram of the prepared copolymers were studied as well for revealing the thermal and crystallinity behavior of the copolymer as LA/PEG mole ratios varied.     

Microwave‐assisted synthesis and characterization of biodegradable block copolyesters based on poly(3‐hydroxyalkanoate)s and poly(D,L‐lactide)

Microwave (MW)‐assisted ring‐opening polymerization (ROP) provides a rapid and straightforward method for engineering a wide array of well‐defined poly(3‐hydroxyalkanoate)‐b‐poly(D,L ‐lactide) (PHA‐b‐PLA) diblock copolymers. On MW irradiation, the bulk ROP of D,L ‐lactide (LA) could be efficiently triggered by a series of monohydroxylated PHA‐based macroinitiators previously produced via acid‐catalyzed methanolysis of corresponding native PHAs, thus affording diblock copolyesters with tunable compositions. The dependence of LA polymerization on temperature, macroinitiator structure, irradiation time, and [LA]₀/[PHA]₀ molar ratio was carefully investigated. It turned out that initiator efficiency values close to 1 associated with conversions ranging from 50 to 85% were obtained only after 5 min at 115 °C. A kinetic investigation of the MW‐assisted ROP of LA gave evidence of its “living”/controlled character under the experimental conditions selected. Structural analyses and thermal properties of biodegradable diblock copolyesters were also performed. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Mechanism of the living lactide polymerization mediated by robust zinc guanidine complexes

Zinc bis(chelate) guanidine complexes promote living lactide polymerization at elevated temperatures. By means of kinetic and spectroscopic analyses the mechanism has been elucidated for these special initiators that make use of neutral N-donor ligands. The neutral guanidine function initiates the polymerization by a nucleophilic ring-opening attack on the lactide molecule. DFT calculations on the first ring-opening step show that the guanidine is able to act as a nucleophile. Three transition states were located for ligand rearrangement, nucleophilic attack, and ring-opening. The second ring-opening step was modeled as a representation for the chain growth because here, the lactate alcoholate opens the second lactide molecule via two transition states (nucleophilic attack and ring-opening). Additionally, the resulting reaction profile proceeds overall exothermically, which is the driving force for the reaction. The experimental and calculated data are in good agreement and the presented mechanism explains why the polymerization proceeds without co-initiators.     

Synthesis and characterisation of lanthanide phenolate compounds and their catalytic activity towards ring-opening polymerisation of cyclic esters

Five new heteroleptic lanthanide(III) phenolate compounds have been synthesised in high yield, four via a transamination reaction between Ln(N(SiMe(3))2)3 and two equivalents of the phenol, HOC(6)H(2)(2,4-Bu(t))-6-CH(2)N(Me)CH(2)CH(2)NMe(2) [corrected] (LH) in thf {L(2)LnN(SiMe(3))2 where Ln = La (1); Nd (2); Sm (3); Yb (4)}. The fifth compound, [L(2)La][BPh(4)] 5 was formed by conversion of 1 by treatment with one equivalent of [Et(3)NH][BPh(4)] in toluene. Compound 3 was subjected to a single-crystal X-ray analysis and revealed a five-coordinate, distorted trigonal bipyramidal samarium(III) metal centre where each phenolate ligand is bidentate coordinating through the phenolate oxygen and nitrogen yielding six-membered chelate rings. Compound 1 exhibited fluxional behaviour in C(4)D(8)O solution which was temperature dependent. All five compounds were assessed as catalyst precursors towards the ring-opening polymerisation of both L-lactide and epsilon-caprolactone. These polymerisation studies revealed that catalysts containing larger lanthanide metals were more efficacious than those with smaller lanthanide metals. Furthermore, replacement of the [N(SiMe(3))2] initiating group in 1 with [BPh(4)] in 5 reduced catalytic activity by this compound. Detailed kinetics analysis of the ring-opening polymerisation of L-lactide by compound 1, the most efficacious catalyst precursor analysed in this study, revealed the following rate law: -d[LA]/dt = k[LA](2)[1](1) which is second order in lactide and first order in catalyst. End-group analysis by ESI mass spectrometry revealed the presence of phenolate end-groups and lactide cycles, the latter formed by intra-molecular, intrachain transesterification.     

乙酰丙酮铁催化丙交酯开环聚合的研究

以乙酰丙酮铁 [Fe(acac) 3]为催化剂进行D ,L 丙交酯的开环聚合及在聚乙二醇 (PEG)存在下的开环共聚 ,研究了催化剂用量、反应温度和反应时间对聚合反应的影响以及PEG用量对共聚反应的影响 ,并探讨了丙交酯开环聚合机理 .结果表明 ,Fe(acac) 3是按配位 插入机理催化丙交酯开环聚合的 ;在本文的聚合条件下 ,大部分聚合的单体转化率都达 90 %以上 ,聚合产物的粘均分子量最高可达 6 6 0 0 0 ,均显示出较好的催化性能 .在PEG存在下 ,PEG作为引发剂参入了丙交酯的开环聚合 ,D ,L 丙交酯是沿着PEG分子两端开环聚合的 ,分子链的链端结构是以羟基为端基的乳酰基结构单元 ,Fe(acac) 3有促进PEG参与聚合成酯的作用 .     

Ultrafast organocatalytic ring-opening polymerization of N-sulfonyl aziridine in the melt

An ultrafast approach for controlled synthesis of well-defined polysulfonamides is established through organocatalytic anionic ring-opening polymerization (ROP) of N-sulfonyl aziridine in the melt. Several different organobases are investigated, and it is found that N,N,N′,N″,N″-pentamethyldiethylenetriamine (PMDETA) catalyzed ROP of 2-methyl-N-tosylaziridine (TsMAz) gives the desired polymer, while 1,4-diazabicyclo[2.2.2]octane (DABCO) and 1,8-diazabicyclo[5.4.0]-undec-7-ene (DBU) initiate the polymerization along with initiator to produce uncontrolled polymers. Using PMDETA as the catalyst, poly(2-methyl-N-tosylaziridine) with molecular weight over 100 kg/mol can be synthesized in less than 90 s. Various initiators, including carboxylic acid, N-sulfonyl amide, unactivated amine, phenol, and thiol, are applicable for this protocol to give the molecular weight and end-group controlled polymers under the open-flask condition. Combining this ultrafast ROP with ring-opening metathesis polymerization (ROMP), a brush copolymer is facile synthesized. This approach allows the ultrafast metal-free synthesis of polysulfonamide and expands the scope of initiators for the ROP of N-sulfonyl aziridines.     

Zinc and magnesium complexes incorporated by bis(amine) benzotriazole phenoxide ligand: synthesis, characterization, photoluminescent properties and catalysis for ring-opening polymerization of lactide

A new bis(amine) benzotriazole phenoxide ligand, (C8NN)BTP-H (1) was prepared from the Mannich condensation of 2-(2H-benzotriazol-2-yl)-4-(2,4,4-trimethylpentan-2-yl)phenol with the mixtures of excess paraformaldehyde and N,N,N-trimethylethylenediamine under reflux conditions. Zinc and magnesium complexes bearing the N,N,O-tridentate (C8NN)BTP ligand were synthesized and fully characterized. The reaction of (C8NN)BTP-H with ZnEt(2) (1.2 molar equiv.) in toluene gives the monomeric tetra-coordinated zinc complex [((C8NN)BTP)ZnEt] (2). The homoleptic and monomeric complexes [((C8NN)BTP)(2)M] (M = Zn (3) and M = Mg (4)) result from treatment of ZnEt(2) or Mg(n)Bu(2) with (C8NN)BTP-H (two equiv.), in which the metal center is hexa-coordinated by two tridentate (C8NN)BTP ligands. Luminescent properties and catalysis for lactide (LA) polymerizations of complexes 2-4 are studied. Complexes 2-4 produce bright green fluorescence with emission maxima ranging from 510 to 520 nm in the solid state. Experimental results indicate that complex 2 catalyzes the ring-opening polymerization of LA in the presence of 9-anthracenemethanol (9-AnOH) with efficient catalytic activities in a controlled fashion, yielding poly(rac-lactide) with a slight isotactic predominance (P(m) = 0.59).     

Ring opening polymerization of lactide promoted by alcoholyzed heteroscorpionate aluminum complexes

The alcoholysis of the heteroscorpionate methyl aluminum complex (bpzmp)AlMe₂ ( 1 ) (bpzmp = 2,4‐di‐tert‐butyl‐6‐(bis‐(3,5‐dimethylpyrazol‐1‐yl)methyl)phenoxo), promoted both by phenol and isopropanol, has been investigated. The reaction of 1 with phenol afforded the dimeric mono(phenoxo) derivative 2 , whereas the alcoholysis of 1 with the less acidic isopropanol involved the coordinated heteroscorpionate ligand and led to the tetrahedral complex 3 in which the aluminum atom is surrounded by one κ²‐N,O^? coordinated bpzmp ligand and one η¹‐O^? coordinated ppzmp ligand (ppzmp = 2,4‐di‐tert‐butyl‐6‐(i‐propoxy‐(3,5‐dimethylpyrazol‐1‐yl)methyl)phenoxo). Complexes 1 – 3 have been tested in the ring opening polymerization (ROP) of L ‐lactide. The dimeric mono(phenoxo) derivative 2 was inactive in the ROP of L ‐lactide. Quite surprisingly, complex 3 was found to be active in ROP of L ‐ and rac‐lactide, showing a good molar‐mass control. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3632–3639, 2010     

Controlled ring-opening polymerization of cyclic esters with phosphoric acid as catalysts

(R)-(?)-1,1′-Binaphthyl-2,2′-diyl hydrogen phosphate (BPA) has been demonstrated as an efficient organocatalyst for controlled ring-opening homopolymerization of ε-caprolactone (ε-CL) and copolymerization of ε-CL with glycolide and lactide. High molar mass PCL with narrow molar mass distribution has also been synthesized from the bulk ring-opening polymerization (ROP) of ε-CL with BPA as catalysts; the highest molar mass of PCL is 4.35?×?10⁴ g/mol with polydispersity index of 1.20. The successful synthesis of high molar mass PCL is attributed to the bifunctional activation mechanism for the ROP of ε-CL catalyzed by BPA. More interestingly, ppm level of BPA is sufficient to catalyze controlled ROP of ε-CL.     

Chemical upcycling of poly(lactide) plastic waste to lactate ester,lactide and new poly(lactide) under Mg-catalysis condition

Chemical upcycling of end-of-life poly(lactide) plastics to lactide, lactate ester and new poly(lactide) has been achieved by using magnesium bis[bis(trimethylsilyl)amide] [Mg(HMDS)₂] as promoter. Mg(HMDS)₂ showed high efficiency in l-lactide polymerization and poly(lactide) depolymerization. Mg(HMDS)₂/Ph₂CHOH catalytic system displayed high ring-opening selectivity and the characteristic of immortal polymerization. Taking advantage of transesterification, depolymerizations of end-of-life poly(lactide) plastics to lactate ester (polymer to value-added chemicals) and lactide (polymer to monomer) were achieved with high yields. Besides, a new “depolymerization-repolymerization” strategy was proposed to directly transform poly(lactide) into new poly(lactide). This work provides a theoretical basis for the design of polymerization and depolymerization catalysts and promotes the development of degradable polymers.     

Complexities in the ring-opening polymerization of lactide by chiral salen aluminum initiators

The preparation of (R, R)- and (S, S)-salen Al(OR) complexes, where R = Et, CH2(i)Pr, CH2(t)Bu, and CH2CH(S)MeCl, are reported, along with their reactions with rac-lactide (salen = N, N'-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediamino). Rapid, reversible coordination of LA to the salen metal complex is observed, and it is shown that the relative rates of alcohol/alkoxide exchange are comparable to the NMR time scale while the rate of chain transfer involving (R, R)-salenAl(O-R-R) and (S, S)-salenAl(O-S-R) is much faster than the initial rate of ring opening of the LA monomer. For a primary [Al-OR] moiety, the ring opening of rac-LA is much faster than the ring-opening polymerization/enchainment of LA, and in the initial ring-opening event, the diastereoselectivity is dependent on the solvent, the chirality of the salen ligand, and the OR group. Irrespective of the initiator group OR or the solvent, the system moves to a pseudostatic equilibrium concentration of L- and D-LA which is dependent on the nature of the chirality of the salen ligand. Further studies show that the relative rate of trans-esterification is slower than the rate of LA enchainment and that the rate of epimerization is the slowest reaction in the system. Adventitious water leads to loss of catalytic activity and formation of the inert oxo-bridged compound [(salen)Al]2(mu-O) which has been structurally characterized.     

Polymerization of (L,L)‐lactide and copolymerization with ϵ‐caprolactone initiated by dibutyltin dimethoxide in supercritical carbon dioxide

Ring‐opening polymerization (ROP) of (L,L)‐lactide (LA) has been initiated by dibutyltin dimethoxide in supercritical carbon dioxide (sc CO₂). Polymerization is controlled and proceeds at quasi the same rate as in toluene, which indicates that the reactivity of the propagating species is not impaired by parasitic carbonation reaction. Random copolymerization of LA with ?‐caprolactone (CL) has also been studied in sc CO₂, and the reactivity ratios have been determined as 5.8 ± 0.5 for LA and 0.7 ± 0.25 for CL. These values have to be compared to 0.7 ± 0.25 for LA and 0.15 ± 0.05 for CL in toluene. Good control on ROP of CL and LA in sc CO₂ has been confirmed by the successful synthesis of diblock copolymers by sequential polymerization of CL and LA. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2777‐2789, 2005