Bimetallic aluminum complexes supported by bis(salicylaldimine) ligand: Synthesis,characterization and ring-opening polymerization of lactide

Two types of bifunctional bis(salicylaldimine) ligands (syn-L and anti-L) were designed and synthesized to support bimetallic aluminum complexes.Owing to the rigid anthracene skeleton,syn-L and anti-L successfully locked two Al centers in close proximity (syn-Al2) and far apart (anti-Al2),respectively.The distance between two Al centers in syn-Al2 was defined by X-ray diffraction as 6.665 (A),which is far shorter than that in anti-Al2.In the presence of stoichiometrical BnOH,syn-Al2 and anti-Al2 were both efficient for ring-opening polymerization (ROP) of rac-LA with the former being more active.In the presence of excess BnOH,syn-Al2 showed an efficient and immortal feature,consistent with high conversions,matched Mns,narrow molecular weight distributions and end group fidelity,while anti-Al2 had a much lower activity or even became entirely inactive due to rapid decomposition,indicated by in situ 1H-NMR experiments of A1 complexes with BnOH.     

Microwave-assisted Polymerization of ε-Caprolactone with Maleic Acid as Initiator and Drug Release Behavior of Ibuprofen-Poly(ε-caprolactone) System

Poly( ε-caprolactone)(PCL) with weight-average molar mass over 10000g/mol was synthesized by microwave-assisted ring -opening polymerization of ε-caprolactone(ε-CL) with maleic acid(MA) as initiator (2.45GHz,360W,85min),Ibuprofen-PCL controlled release system was prepared directly by the ROP of ε-CL in its mixture with ibuprofen.The release of ibuprofen from the system was sustained and steady.     

Polymerization of lactic <Emphasis Type="Italic">O</Emphasis>-carboxylic anhydride using organometallic catalysts

The ring-opening polymerization of 5-methyl-1,3-dioxolane-2,4-dione(lactic O-carboxylic anhydride,LacOCA) using organometallic complexes,including Co(Ⅲ) complexes with Schiff base ligands,Tin(Ⅱ) alphatates and Al(Ⅲ) complexes with Schiff base ligands,was explored.The polymerization was carried out by treatment of the organometallic complexes with LacOCA in toluene under mild conditions.The corresponding poly(lactic acid) was characterized by spectroscopy and thermal analyses,which revealed insight into the structure of the effective catalyst for the polymerization of LacOCA.     

稀土硫化物：e–己内酯开环聚合新催化剂

The ring-opening polymerization （ROP） of ε-caprolactone （ε-CL） using lanthanide thiolate complexes [（CH3CsH4）2Sm（μ-SPh）（THF）]2 （1） and Sm（SPh）3（HMPA）3 （2） as initiators has been investigated for the first time. Both of 1 and 2 were found to be highly efficient initiators for the ROP of ε-CL. The poly（ε-caprolactone） （PCL） with molecular weight Mn up to 1.97 ×10^5 and relatively narrow molecular weight distributions （1.20〈MW/Mn〈 2.00） have been obtained in high yield in the temperature range of 35-65℃. According to the polymer yield, 2 showed much higher activity than 1. However, the number-average molecular weight of PCL obtained with 2 was much lower than with 1. The possible polymerization mechanism of the ε-CL polymerization has been proposed based on the results of the end group analysis of the ε-CL oligomer.     

Controlled/living ring-opening polymerization of ε-caprolactone catalyzed by phosphoric acid

The bulk ring-opening polymerization(ROP) of ε-caprolactone(ε-CL) by various phosphoric acids using phenylmethanol as the initiator was conducted.1,1’-bi-2-Naphthol(BINOL)-based phosphoric acid was found to be an effective organocatalyst for ROP leading to polyesters at 90℃.The overall conversion to poly(ε-caprolactone) was more than 96% and poly(ε-caprolactone) with M w of 8400 and polydispersity index of 1.13 was obtained.1 H NMR spectra of oligomers demonstrated the quantitative incorporation of the protic initiator in the polymer chains and showed that transesterification reactions did not occur to a significant extent.The controlled polymerization was indicated by the linear relationships between the number-average molar mass and monomer conversion or monomer-to-initiator ratio.In addition,the present protocol provided an easy-to-handle,inexpensive and environmentally benign entry for the synthesis of biodegradable materials as well as polyesters for biomedical applications.     

Lanthanum heterocyclic Schiff-base complex initiated ring-opening polymerization of ε-caprolactone

Lanthanum complex supported by the heterocyclic Schiff-base ligand of N-(2-pyridyl)-3,5-di-tert-butyl-salicylaldimine was prepared and employed for the ring-opening polymerization(ROP)ofε-caprolactone(ε-CL).The polymers obtained with this initiator showed a unimodal molecular weight distribution implied that only one active species was present.Mechanism study revealed that the polymerization proceeds via acyl-oxygen bond cleavage.     

HETEROCYCLIC SCHIFF BASE NEODYMIUM COMPLEX AS CATALYST FOR RING-OPENING POLYMERIZATION OF ε-CAPROLACTONE

An aromatic heterocyclic Schiff base neodymium complex bearing thiazole was synthesized and its activity in the ring-opening polymerization ofε-caprolactone(CL)was examined.The conditions of the CL/Nd molar ratio,monomer concentration,polymerization time and temperature were investigated.Activities of ca.171 kg/Nd·h were obtained under the optimum condition(CL/Nd=1600(molar ratio),[CL]=2.26 mol L~(-1),1 h at 50℃),giving a poly(ε-caprolactone)(PCL)of number-average molecular weight M_n=5.4×10~4 and molecular weight distribution MWD=1.96.The conversion of CL monomer as high as 94% was observed after polymerized for one hour.The mechanism of coordination polymerization has also been illustrated.     

Living polymerization of 1,3-butadiene catalyzed by half-titanocene complex bearing dibenzhydryl-substituted aryloxide ligand

Half-titanocene complexes bearing dibenzhydryl-substituted aryloxide ligands(2a-2d) were prepared. Among them, 2c adopted a three-legged distorted tetrahedral geometry evidenced by X-ray crystallography. The poly-1,3-butadiene with high molecular weight and narrow molecular weight distribution was obtained by using these complexes as the catalysts activated with methylaluminoxane(MAO). The catalytic activities of the complexes depended on their structures. The Ti―O―C bond in the complexes with large angle afforded them with higher activity, while Cp*-based complexes exhibited lower activities than the Cp-based analogues. The activity of complex increased with increasing the polymerization temperature while the selectivity remained no change, indicating the high thermal stability. Furthermore, the polymerization of 1,3-butadiene catalyzed by 2a/MAO at 0 °C has been found in a living fashion.     

Oligomerization and Polymerization of Ethylene Initiated by a Novel Ni(Ⅱ)-Based Acetyliminopyridine Complexes as Single-Site Catalysts

Novel Ni(Ⅱ)-based acetyliminopyridine complexes 1b, 2b, 3b (1-3b), which are synthesized from ligands 1a, 2a, 3a (1-3a) and [NiCl2(DME)], are suitable precursors for the catalysts that are necessary for ethylene oligomerization and polymerization reactions, activated by methylaluminoxane (MAO). The MAO-treated 1-3b presents an active catalytic center, which may oligomerize and polymerize ethylene to produce linearα-olefins and polyethylene, respectively. The molecular weight distributions of oligomers that are obtained are in good agreement with the Schulz-Flory rules for oligomers>C4. The activity of 3b-MAO complex is 6.3×107 g/(molNi·h) at 50℃. The activities and molecular weight distributions of oligomers show significant reliance on the structures of catalyst precursors.     

Synthesis and Molecular Structure of Phosphorus-Sulfur Hybrid Atom Ligand and Their Palladium Complexes With the Studies on the C—H Bond Activation and Photochemical Carbonylation Reaction of Benzene

In this paper, a novel and ideal synthetic method of the phosphorus and sulfur hybrid atom ligand is reported. The speciality of this method is that the by-products of some reactions could be used circularly as starting materials in the synthetic route. Further, we synthesized a series of organopalladium complexes containing these hybrid atom chelate ligands, among them the molecular structures of novelorganopalladium complexes Pd((i-Pr)_2-P(CH_2)_2SEt)Cl_2, Pd(Et_2P(CH_2)_2SEt)Cl_2 and Pd(Ph_2P(CH_2)_2SEt)Cl_2 were determined by using the X-ray single crystal diffraction method. We first used the organotransition metal complexes containing phosphorus and sulfur hybrid atom ligands to activate the σ-C—H bond, and researched the catalytic activity, i.e. the photochemical carbonylation of benzene was catalyzed by these palladium complexes.     

Mono-and Binuclear Cobalt(Ⅱ) Complexes Supported by Quinoline-2-imidate Ligands:Synthesis,Characterization,and 1,3-Butadiene Polymerization

A series of mono-and binuclear Co(II) complexes(Co1–Co7) supported by quinoline-2-imidate ligands were synthesized and thoroughly characterized.Measured by single crystal X-ray crystallography,complexes Co1 and Co3 adopted distorted tetrahedral structures around the cobalt center.Upon activation by ethylaluminium sesquichloride(EASC),these cobalt complexes exhibited high catalytic activity and cis-1,4-selectivity towards 1,3-butadiene polymerization.The effects of ligand environment,polymerization temperature,and cocatalyst types on the polymerization were investigated in detail.Interestingly,the binuclear Co(II) complexes exhibited high thermal stability,and the polymer yields were up to 97.2% even at a high temperature of 70 °C.     

AN APPROACH TO SYNTHESIZE POLY(ETHYLENE GLYCOL)-b-POLY(ε-CAPROLACTONE) WITH TERMINAL AMINO GROUP via SCHIFF’S BASE AS AN INITIATOR

A new method to synthesize a degradable terminal amino group-containing copolymer,poly(ethylene glycol)-b- poly(ε-caprolactone)(MPEG-PCL-NH_2),was developed in the following three steps:(1)the ring-opening polymerization (ROP)ofε-caprolactone from the Schiff base prepared from benzatdehyde and ethanolamine(Ph-CH=NCH_2CH_2OH)used as an initiator to obtain heterobifunctional poly(ε-caprolactone)with one terminal Schiff base group and one hydroxyl group (HO-PCL-CH_2CH_2N=CH-Ph);(2)the coupling reaction of two reactive precursors,a hydroxy-terminated HO-PCL- CH_2CH_2N=CH-Ph andα-monocarboxy-ω-monomethoxy poly(ethylene glycol)(CMPEG)to synthesize MPEG-PCL- CH_2CH_2N=CH-Ph;(3)the conversion of the -N=CH-Ph end-group into NH_2 end-group by acidification of acetic acid to obtain MPEG-PCL-NH_2.The structures from the precursors to the terminal amino group-containing copolymer were confirmed by ~1H-NMR and their molecular weights were measured by gel permeation chromatography.The amphiphilic terminal amino group-containing copolymer could self-assemble into micelles in an aqueous system with PCL block as the core and PEG block as the shell.The micelle formation of the terminal amino group-containing block copolymer was studied by fluorescent probe technique and the existence of critical micellar concentration(cmc)confirmed the amphiphilic nature of the resulting copolymer.ESEM and DLS analysis of the micelles revealed a homogeneous spherical morphology and a unimodal size distribution.     

Effect of surface acidity and pore size of Al-substituted plugs-containing SBA-15 and MCM-41 silicas on the polymerization of THF

We reported here the simultaneous influence of surface acidity and pore size of Al-substituted hexagonal mesoporous silicas(Al-doped plugs-containing SBA-15 and Al-doped MCM-41) on polymerization of THF.These materials were directly synthesized by introduced aluminum isopropoxide into reaction mixture including surfactant and siliceous precursor.Al-doped plugs-containing SBA-15(denotes as PAS) samples not only possess typical two-step desorption isotherms,which implied PAS materials generated plugs in their mesochannel,but also exhibit larger pore size and thicker wall than that of Al-doped MCM-41(denotes as ACM), which implied PAS would have a great advantage on catalytic reaction involving large molecular(e.g.polymer of THF) in industrial point of view.To investigate catalytic activity of PAS and ACM with moderate acidic sites the polymerization of THF in the presence of acetic anhydride was carried out.The results showed PAS exhibiting good performance on polymerization of THF.Such result could be related to the large pore size and moderate acidic sites.     

Mononuclear and Dinuclear Yttrium Complexes Supported by Pyrrolide Ligands: Syntheses,Structures and Catalytic Behaviors towards the Ring-opening Polymerization of ε-Caprolactone

The syntheses, structures and catalytic activities of two yttrium complexes supported by pyrrolide ligands are reported. Treatment of Y(N(Si Me3)2)3 with one equivalent of H3bptd(H3bptd = 1,9-bis(2-pyrrolyl)-2,5,8-triazanona-1,8-diene) in THF gave a complex of composition [Y(bptd)(THF)]2(1). Reaction of Y(N(Si Me3)2)3 with one equivalent of H3tpa(H3tpa = tris(pyrrolyl-?-methyl)amine) in THF generated [Y(tpa)(THF)3](2) in good yield. Complexes 1and 2 have been characterized by single-crystal X-ray diffraction, elemental analyses and NMR spectroscopy. Complex 1 is dinuclear. The two metal centers are doubly bridged by two amine nitrogen atoms to form a Y–N–Y–N four-membered rhombus ring. The geometries of Y3+ ions in 1and 2 are well described as pentagonal bipyramid and capped octahedron, respectively. The ring-opening polymerization reactions of ?-caprolactone initiated by 1 and 2, respectively, were investigated. They both exhibited good catalytic activity for the polymerization of ?-caprolactone. All of the obtained polymers have high molecular weights and relatively narrower PDIs. The polymers generated by 2 possessed polydispersity close to 1.1. The good catalytic activities of 1 and 2 reveal their potential applications in polymer industry.     

POLYMERIZATION OF ETHYLENE WITH UNSYMMETRIC 2,6-BIS(IMINO)PYRIDINE IRON(Ⅱ)COMPLEX

An unsymmetric 2,6-bis(imino)pyridine iron(II) complex 1' was synthesized. The relationship between catalyststructure and its activity in ethylene polymerization is discussed. The kinetic behavior of ethylene polymerization and theeffects of polymerization conditions such as temperature, aluminum/iron molar ratio on the activity of catalyst and thecharacteristics of polyethylene were reported. The unsymmetric catalyst 1' has a good catalytic performance of 3.47×10~6 gPE·mol~(-1)·Fe·h~(-1) at 40℃ with aluminum/iron molar ratio = 2500. A dependence of catalyst activity on themethylaluminoxane (MAO) concentration and reaction temperature was found. The molecular weight (MW) of polyethylenewith broad dispersity is about 10~4-10~5 g/mol. The melting temperature and branching of polyethylenes vary with changingreaction temperature and aluminum/iron molar ratio.     

VINYL POLYMERIZATION OF NORBORNENE CATALYZED BY [2-(2-BENZIMIDAZOLYL)-6-((1-ARYLIMINOETHYL)PYRIDYL)]NICKEL CHLORIDE/MAO SYSTEM

The catalytic system of[2-(2-benzimidazolyl)-6-((1-aryliminoethyl)pyridyl)]nickel chloride/MAO(methylalu- minoxane)was found to be good active for vinyl polymerization of norbornene and provided polymers with relative narrow molecular distributions.Various reaction parameters,such as the ratios of nickel precursor to MAO or monomer norbornene, and the nature of the ligands in complexes were carefully investigated to realize their effects on the catalytic activities, polymer molecular weight and molecular...     

Aluminum and Titanium Complexes Containing Pyrrole-imine Ligands: Syntheses,Structures, and Ring-opening Polymerization of ε-Caprolactone

Syntheses and properties of aluminum and titanium complexes incorporating the pyrrole-imine ligands, N-((~1H-pyrrol-2-yl)methyl)-1-(~1H-pyrrol-2-yl)methanimine(H_2L1) and 2-cyano-~1H-pyrrole(HL2), have been investigated. Addition of one equiv of H_2L1 to AlMe3 and AlEt_3, respectively results in the formation of dinuclear complexes [Al2(L1)2 Me2](1) and [Al2(L1)2 Et2](2). Treatment of Ti(NMe2)4 with one equiv of HL2 and two equiv of iPrOH or three equiv of BnOH results in the production of complexes [Ti(HL3)2(OiPr)2](3) and [Ti2(HL3)2(OBn)6](4)(H_2L~3 = N,N-dimethyl-~1H-pyrrole-2-carboximid-amide). HL_3 anion is an intermediate which is in situ formed from the reaction of HL2 and Ti(NMe2)4. The structures of 1～4 were characterized by single crystal X-ray diffraction. The catalytic properties of 1～4 toward ring-opening polymerization(ROP) of ε-caprolactone were studied. All of the compounds could effectively initiate the polymerization reactions with good activities.     

RING-OPENING POLYMERIZATION OF ε-CAPROLACTONE BY LANTHANOCENE CATALYSIS*

Ring-opening polymerization of ε-caprolactone (CL) catalyzed bylanthanocenes, O(C_2H_4C_5H_3CH_3)_2YCl (Cat-YCl) and Me_2Si[(CH_3)_3SiC_5H_3]_2NdCl(Cat-NdCl) has been carried out for the first time. It has been found that both yttroceneand neodymocene are very efficient to catalyze the polymerization of CL, giving high molec-ular weight poly (ε-caprolactone) (PCL ). The effects of [cat] / [ε- CL] molar ratio, polymeriza-tion temperature and time, as well as solvents were investigated and polymerization tem-perature is found to be the most important factor affecting the polymerization. The bulkpolymerization gives higher molecular weight PCL and higher conversion than that in solu-tion polymerization. NaBPh_4 was found to promote the polymerization of ε-caprolactone,and thus to increase both the polymerization conversion and MW of poly (ε- caprolactone ).     

In situ generation of biodegradable poly(p-dioxanone) micro-particles by polymerization in supercritical carbon dioxide

Ring-opening suspension polymerization of p-dioxanone（PDO） in supercritical carbon dioxide（scCO₂） was investigated in the presence of poly（caprolactone）-perfluropolyether-poly（caprolactone）（PCL-PFPE-PCL）.The molecular weight,yield and particle morphology of poly（p-dioxanone）（PPDO） were studied.The stabilizer was effective to stabilize the ring-opening polymerization（ROP） of PDO in scCO₂,leading to the formation of resorbable microparticles in a"one pot"procedure.The mean size of PPDO microparticles obtained from suspension polymerizations was sensitive to the rate of agitation and the stabilizer concentration.The method to generate PPDO microparticles has overcome its unprocessable drawback with common organic solvents and provided new product form for biomedical applications.     

–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.