【作者】 余淑娴；

【导师】 洪三国； 陈义旺；

【作者基本信息】 南昌大学 ， 工业催化， 2014， 博士

【摘要】 聚烯烃材料是聚合物中产量最大、用途最广、发展最快的品种,对人类的进步与发展起着越来越重要的作用。催化剂是聚烯烃生产的核心技术,随着人们对催化剂结构与聚合物微观结构及性能认识的不断深入，必将对催化剂的分子设计、聚烯烃材料结构性能改善以及产业化的推进起到重要的作用。本文在实验的基础上，应用理论计算的方法，从分子和电子水平深入探究反应本质，研究催化烯烃的活化过程和聚合反应机理及影响催化活性的关键因素。1、使用后过渡金属络合物催化剂双-(-酮胺)镍(II)催化剂，与助催化剂甲基铝氧烷组成新型催化体系，催化苯乙烯单体聚合反应。在实验的基础上，采用密度泛函的方法，研究该催化体系催化苯乙烯聚合的反应机理。研究表明，苯乙烯的活化对反应的进行起着关键作用，该反应是一个四圆环的反应机理，中心离子，C=C双键和R基团构成一个四圆环。在苯乙烯聚合反应中，随着碳链的增长，反应的立体位阻增加，其活化能垒也逐渐升高。这和实验的聚合物为中等分子量观察是一致的。2、用双-(-酮胺)镍(II)络合物体系催化降冰片烯聚合。基于实验研究的基础上，采用密度泛函的方法，对上述反应进行研究，结果表明相对苯基取代基而言，萘基取代的配体催化剂由于具有较强的电子离域能力，导致其中心离子的正电荷增加较大，因此具有较强的亲电能力，催化剂活性也因此较高。研究还表明，当苯基上取代基为吸电子基团时，其活化能垒较低，催化剂的活性会大大加强。3、对双金属镍催化剂催化烯烃聚合反应的理论研究。着重研究了反应过程中双中心金属离子之间的相互协同作用。发现反应过程中，β-氢与Ni5中心原子有比较强的相互作用，其过渡态的能量大大降低，相邻的金属中心对增加聚合的动力学速率，增加聚合反应中链的长度起着很重要的作用。两个Ni中心对该类催化聚合反应都是很重要的，其中一个是主催化中心，一个是副催化中心，两者协同作用。4、采用B3LYP方法，计算了双锡化合物Ar′SnSnAr′和Ar*SnSnAr*的分子结构、电子结构以及其与乙烯的反应性能。结果表明Ar　S nSnAr　和Ar*SnSnAr*存在不同的稳定自旋态：对于Ar′SnSnAr′，其基态是两个中心芳环几乎与C(ipso)SnSnC(ipso)共平面的单重态；对于Ar*SnSnAr*,其基态是两个中心芳环与C(ipso)SnSnC(ipso)互相垂直的的三重态；研究表明Ar′SnSnAr′与Ar*SnSnAr*，由于都存在势能面交叉点，因此会产生系间窜越，单重态和三重态之间可以相互转化。此外，Ar′SnSnAr′和Ar*SnSnAr*的三重态分别与乙烯反应均会经过一个优势协同反应通道，然后经过势能面交叉点而得到单重态产物，同时发现该催化剂对烯烃有较强的活化作用。更多还原

【Abstract】 Polyolefin material is a variety with largest yield and widest applications amongpolymers, which plays more and more important roles in human progress anddevelopment. Moreover catalysis is a core technology for production of polyolefin.Novel catalytic systems involving mono-anionic or neutral, bidentate or tridentate,oxygen-, nitrogen-, or phosphorus-containing chelating ligands have recently beendescribed for ethylene polymerization and are still being investigated. In fact， thereaction mechanism will play a vital role in catalyst designing, andimprovement the performance of polyolefin material. In this article, we wouldexplore reaction mechanism at molecular and electron level as well as key factors thateffect catalytic activity by combining experimental and theoretical methods..1. Styrene was polymerized by using bis (b-ketoamino) nickel (II) complex asthe catalyst precursor and methylaluminoxane (MAO) as the cocatalyst. At same time,styrene polymerization using (2Z,4E)-4-(methylimino)-pent-2-en-2-ol Ni (MPNi)catalyst has been studied using density functional theory at the B3LYP/6-31g (d, p)level. In particular, the reaction mechanisms have been investigated in detail. Theresults indicate that the reaction involves a four-mamboed cyclic transition state withan energy barrier of21.63kcal mol-1. In addition, the analysis indicates that strongp-d interactions between styrene and Ni2+are very important for the activation ofstyrene.2. Norbornene polymerizations proceeded with bis(b-ketoamino)-nickel(II){Ni[CH3C(O)CHC(NR)CH3]2[R=phenyl (1) or naphthyl (2)]} complexes as thecatalyst precursors and the organo-Lewis compound tris(pentafluorophenyl)borane[B(C6F5)3] as a unique cocatalyst. From our calculations, comparing with phenyl assubstituent group of ligand, the naphthyl has strong electron delocalization ability.Because the positive charge of central ion will increase sharply, it possesses strongelectrophilic capacity and the catalyst activity is also high. The study also shows thatwhen substituent group of phenyl is electrondrawing group, the catalyst activitywould be enhanced greatly. 3. In this part, we have studied bimetallic effects in the reaction of ethylenepolymerization for enhanced polar comonomer enchainment selectivity. The studiedshowed the hydrogen bond between H atom of alkane and Ni atom is that thebimetallic catalysts exhibit significantly higher activities than the monometalliccatalysts. Mechanistic studies confirm that, polymerizations follow a coordinativeinsertion process, with enhanced monomer enchainment facilitated by the secondcatalytic center4. The molecular structure and electronic structure of Ar′SnSnAr′andAr*SnSnAr*as well as their reaction activity with ethylene were studied by usingB3LYP DFT calculations in the present paper. The results show that Ar′SnSnAr′andAr*SnSnAr*have different stable spin state. For Ar’SnSnAr’, the singlet state isground state with a planar structure (PL) that the plan of two central aryl rings areparallel and almost in a plane. However, for Ar*SnSnAr*, the triplet state is groundstate with a perpendicular structure (PE), the plan of two central aryl rings areperpendicular with each other. The result shows that the singlet and triplet statestabile stations are able to transfer to each other by crossing points of PES. Ourcalculation also indicates that both Ar’SnSnAr’ and Ar*SnSnAr*reacts withethylene to via a concert reaction channel of triplet state via3TS3that was followedby a potential energy surfaces crossing point to reach to the product of singlet state.For the stepwise channel, both triplet and singlet potential energy surfaces holdhigher energy barrier than their in the concerted reactions.更多还原