Cyclization in situ of isoprene polymerization catalyzed by Nd-Al bimetallic complex

Function of chloride and effect of various alkylaluminiums, C1/A1 molar ratio, solvents on cyclization in situ of isoprene polymerization catalyzed by Nd-Al bimetallic complex were studied. The structure of cyclized products was characterized by means of IR and H-1 NMR, The results indicated that in the course of isoprene polymerization with rare earth catalytic system, the function of alkylchloride introduced is terminating cis-polymerization and generating cationic species with alkyl-aluminums to initiate cyclization in situ. Soluble cyclized polyisoprene was obtained with fragments of cyclopolyisoprene.

Theoretical studies of nonlinear optical properties of compounds K(4)Ln(2)(CO3)(3)F-4 (Ln=Pr, Nd, Sm, Eu, Gd)

K(4)Ln(2)(CO3)(3)F-4 (Ln=Pr, Nd, Sm, Eu, Gd) is a special type of frequency doubling compound, whose crystal structure exhibits a scarcity of fluorine ions. This leads to two different coordination polyhedrons in the general position of K(2) atoms: [K(2)O6F(1)(2)F(2)] and [K(21)O6F(1)(2)] in a 2/1 ratio. The chemical bonding structures of all constituent atoms of the compound K4Gd2(CO3)(3)F-4 (KGCOF) are comprehensively studied; moreover, the relationship between the chemical bonding structure and the nonlinear optical (NLO) properties is investigated from the chemical bond viewpoint. The theoretical prediction of the NLO tensor coefficient d(11) of KGCOF is in agreement with experimental observation. Theoretical analyses show that the nonlinearity of this crystal type mainly originates from K-O bonds. In addition, the correlation between the NLO tensor d(11) and the refractive index n(0) of KGCOF is discussed. (C) 2000 American Institute of Physics. [S0021-8979(00)07506-X].

激光晶体Nd:KGW晶体的表面缺陷观察

本文采用助熔剂籽晶提拉法生长出了Nd :KGW激光晶体。利用光学显微镜对晶体表面进行观察、并拍摄到晶体裂缝、生长丘、生长条纹和包裹物等缺陷的照片。分析其原因 ,是由于晶体生长工艺的不稳定 ,尤其是晶体生长过程中的温度梯度不够合适、提拉速度过快、降温速率偏快等所致。并由于生长体系粘度较大 ,容易形成包裹 ,晶体包裹物经XRD分析认为其中主要是熔体。

Synthesis and crystal structure of [Nd(eta(6)-1,3,5-C6H3Me3)(AlCl4)(3)]( C6H6) and structural comparison of Ln(eta(6)-arene)(AlCl4)(3)

Reaction of NdCl3, with AlCl3 and mesitylene in benzene gives complex [Nd(eta (6)-1,3,5-C6H3Me3) (AlCl4)(3)] (C6H6) (1) which was characterized by elemental analysis, IR spectra, MS and X-lay diffractions. The X-ray determination indicates that 1 has a distorted pentagonal bipyramidal geometry and crystallizes in the monoclinic, space group P2(1)/n with a = 0.9586(2), b = 1.1717(5), c = 2.8966(7) nm, beta = 90.85 (2)degrees, V = 3.2529(6) nm(3), D-c = 1.573 g/cm(3), Z = 4. A comparison of bond parameters for all the reported Ln(eta (6)-Ar) (AlCl4)(3) complexes indicates that the bond distance of Ln-C is shortened with the increasing of methyl group on benzene and with the decreasing of radius of lanthanide ions.

The influence of bond valence on bond covalency in RMn2O5 (R=La, Pr, Nd, Sm, Eu)

The relationship between bond valence and bond covalency in RMn2O5 (R = La, Pr, Nd, Sm, Eu) has been investigated by a semiempirical method. This method is the generalization of the dielectric description theory of Phillips, Van Vechten, Levine and Tanaka scheme. The results indicate that larger valences usually result in higher bond covalencies, in good agreement with the point that the excess charge in the bonding region is the origin of formation of bond covalency. Other factors, such as oxidation state of elements, only make a small contribution to bond covalency.

The effect of preparation conditions on the catalyst Nd(P-507)(3)/H2O/Al(i-Bu)(3) for the polymerization of styrene

The catalyst system neodymium phosphonate Nd(P-507)(3)/H2O/Al(i-Bu)(3) for the polymerization of styrene was examined. Effects of the addition order of the catalyst components, catalyst aging time and aging temperature on the catalyst activity and the polymer characteristics were investigated. The catalyst activity for isospecific polymerization of styrene increases with aging time and reaches the maximum with a catalyst aged for 45 min at 70 degrees C. The aging time that the catalyst needs to reach the highest activity for isospecific polymerization decreases with increasing aging temperature. The preformed catalyst and the in situ catalyst were compared with respect to the kinetic behavior of the styrene polymerization and the polymer characteristics.

Synthesis and x-ray structure of a highly symmetrical selenium-centered hexanuclear neodymium complex, [(Cp6Nd6Se13)-Nd-t](-) (Cp-t=eta(5)-(BuC5H4)-C-t)

The half-sandwich tert-buthylcyclopentadienyl neodymium complex [(CpNdCl2)-Nd-t(THF)(2)](2) (1) reacts with Na2Se5 to give organoneodymium polyselenide complex [Na(THF)(6)][(Cp6Nd6)-Nd-t(mu(6)-Se)(mu(2)-Se-2)(6)] (2) which has been characterized by X-ray crystallography.

Structural analysis of nonlinearities of Ca4ReO(BO3)(3) (Re = La, Nd, Sm, Gd, Er, Y)

From the chemical bond viewpoint, second-order nonlinear optical (NLO) tensor coefficients of the family of new oxoborates Ca4ReO(BO3)(3) (CReOB, Re = La, Nd, Sm, Gd, Er, and Y) have been theoretically predicted. The d(11) tensor coefficient of CReOB is predicted to be -11 d(36)(KDP), which is the largest d(ij) tensor that has been found in borate crystals. From the structural characteristic of CReOB, we find the isolated BO33- clusters play a dominant role in contributions to the total nonlinearity, and the largest d(11) tensor of CReOB-type crystals is also ascribed to these BO33- clusters. We also find the NLO property of this family does not change dramatically for different rare-earth elements. The details of the calculation of CGdOB only are presented.

Nd-Al双金属配合物催化双烯聚合反应动力学

以Nd-Al双金属配合物为催化剂，考察了丁二烯和异戊二烯聚合反应的动力学，得到稳态聚合速率方程式为RP＝K［M］[ND］ｎ（ｎ＝１）；丁二烯比异戊二烯有更大的表观增长速率常数ｋ．这些与聚合体系中是否存在过量的烷基铝无关．对多组分稀土催化剂作用下异戊二烯聚合反应动力学方程中出现较高ｎ值的现象进行了初步的探讨

Crystal growth and TG-DTA properties of K(2)Ln(NO3)(5).2H(2)O (Ln = La, Ce, Pr, Nd, Sm)

Single crystals of KLnN(Ln=La, Ce, Pr, Nd, Sm) can be grown in water solution with pH approximate to 1 similar to 2 at about 40 degrees C. Crystals of KLnN (Ln=La, Ce, Pr, Nd) are orthorhombic with space group Fdd2. KPrN crystal was grwon and its crystal structure was determined for the first time. The KPrN crystal parameters obtained by the direct method are as follows: a=21.411(3) Angstrom, b=11.2210(10)Angstrom, c=12.208(2) Angstrom, Z=6, R=0.0240. The TG-DTA curves of KLnN(Ln=La,Ce, Pr, Nd, Sm) demonstrate that the processes of dehydration, melt, irreversible phase transition and decomposition of NO3- take place in sequence with the temperature increasing(except KCN). There are three steps in the decomposition of NO3- in KLnN(Ln=La, Nd, Sm) while two steps in KLnN (Ln=Ce, Pr). K(2)Ln(NO3)(5). 2H(2)O are formed at about 225 degrees C by the reaction of the starting materials of KNO3 and Ln(NO3)(3). nH(2)O.

K_2Ln(NO_3)5·2H_2O(Ln=Pr,Nd)的晶体结构和非线性光学性质

本文采用水溶液中生长晶体的方法合成了ＫＬｎＮ（Ｌｎ＝Ｐｒ，Ｎｄ）的单晶，研究了ＫＰｒＮ的单晶结构及ＫＬｎＮ（Ｌｎ＝Ｐｒ，Ｎｄ）的非线性光学性质。ＫＬｎＮ（Ｌｎ＝Ｐｒ，Ｎｄ）均属正交晶系，Ｆｄｄ２空间群。ＫＰｒＮ的晶胞参数为：ａ＝２．１４１１（３）ｎｍ，ｂ＝１．１２２１０（１０）ｎｍ，ｃ＝１．２２０８（２）ｎｍ，Ｚ＝６，Ｒ＝０．０２４０．ＫＬｎＮ（Ｌｎ＝Ｐｒ，Ｎｄ）的二次谐波光强与ＫＬｎＮ（Ｌｎ＝Ｌａ，Ｃｅ）处于同样的数量级．ＫＬｎＮ容易生长出大尺寸晶体，是一类有应用前景的可产生蓝绿光的倍频转换材料。

K_2Ln(NO_3)_5·2H_2O(Ln=La,Ce,Pr,Nd,Sm)的晶体生长和热重-差热分析研究

本文生长出了K2Ln（NO3）5.2H2O（Ln=La；Ce；Pr；Nd；Sm）的单晶，并对其进行了晶体结构及差热-热重分析研究．结果表明，K2Ln（NO3）5.2H2O（Ln=La；Ce；Pr；Nd）的晶体属正交晶系，Fdd2空间群．首次生长出KPrN单晶并用直接法解出其晶体结构．解得KPrN的晶胞参数为：a=11．2210（10）,b=21．411（3），c=12．208（2）,Z=6；R=0．0240．对KLnN加热，则依次出现脱水、熔化、不可逆相变和NO的分解过程（K2Ce（NO3）5·2H2O除外）K2Ln（NO3）5·2H2O（Ln＝La；Nd；Sm）的NO分三步分解，K2Ln（NO3）5·2H。O（Ln=Ce；Pr）的NO分两步分解·KNO3和Ln（NO3）3·nH2O的混合物在225℃左右生成K2Ln（NO3）5

YAG:Nd,Ho光谱性质的研究

YAG是一种多用途的激光基质材料。由于YAG的机械、热学和光学等物化综合性能良好,迄今为止它仍是最佳的掺稀土离子的固体基质材料,特别是Nd:YAG能在室温下以四能级方式、脉冲或连续工作,阈值低,效率高,是应用最广泛的激光材料之一。

An eta(6)-toluene complex of neodymium: [Nd(eta(6)-C6H5CH3)(AlCl4)(3)]

The Nd-III ion in hexa-mu-chloro-1:2 kappa(2)Cl;1:3 kappa(2)Cl;1:4 kappa(2)Cl-hexachloro-2 kappa(2)Cl,3 kappa(2)Cl,4 kappa(2)Cl- [1 (eta(6))- toluene] trialuminiumneodymium has distorted pentagonal bipyramidal coordination geometry. Five Cl atoms form the equatorial plane, and the toluene ring and the sixth Cl atom occupy the apical sites. The average Nd-C(eta(6)) and Nd-Cl distances are 2.926 (5) and 2.857 (1) Angstrom, respectively.

The polymerization of methyl methacrylate with a new Nd(O-i-Pr)(3)-Al(i-Bu)(3) catalyst system

Methyl methacrylate (MMA) was polymerized with the rare earth coordination catalyst-system of Nd(O - i-Pr)(3) in toluene. The influences of various ligands in neodymium complexes, molar ratio of Al/Nd, catalyst concentration, catalyst aging time, solvents, the third component CCl4, temperature and time on the polymerization of MMA were studied. The results showed that the polymerization conversion reached more than 80% at a catalyst concentration of 9.2 x 10(-3) mol/L. The appropriate molar ratio of CCl4/Nd was 4. Hydrocarbon was preferred for the polymerzation to obtain a high conversion and a high <(M)over bar w> of PMMA. The H-1 NMR spectra of PMMA indicated that the lower the temperature, the higher the syndiotactic content of PMMA was obtained.