Fan Yuguo

CRYSTAL-STRUCTURE OF NDCL3.4THF AND ITS CATALYTIC ACTIVITY IN POLYMERIZATION OF DIENE

Abstract The crystal and molecular structures of NdCl 3 · 4THF have been determined by the low temperature (−60 °C) X-ray diffraction method. NdCl 3 ·4THF recrystallizes in the monoclinic space group P 2 1 / c with unit cell parameters a = 9.404(4), b = 21.591(5), c = 11.751(3) A, β = 111.03(3)°, Z = 4. The final R value is 0.039. Three chlorine atoms and four oxygen atoms from THF are coordinated with the central Nd(III) ion to give a pentagonal bipyramid polyhedron with coordination number 7, the average NdCl bond length is 2.674 A and NO 2.498 A. When combined with aluminum alkyls, NdCl 3 · 4THF is a highly effective catalyst for the polymerization of dienes. Relationships between complex structures and polymerization activities are discussed and the difference in polymerization activities between NdCl 3 and NdCl 3 ·4THF is related to their crystal stabilities.

Hydrothermal synthesis, structure and quantum chemistry of transition metal complex supported by metal-oxo cluster ({Ni(phen) 2 } 2 (ξ-Mo 8 O 26 ))

A nickel-1,10-phenanthroline complex supported on an octamolybdate, [(Ni(phen)2 2(ξ-Mo8O26)], has been hydrothermally synthesized with MoO3, H2MoO4, Ni(OAc)2 6H3O and 1,10-phenathroline (1,10-phen) as raw materials. The crystals of the compound belong to monoclinic P21/n space group,a = 1.2952(2),b = 1.6659(10),c = 1.3956(12) nm, β =106.273(8)°,V = 2.8906(5) nm3,Z = 2. 5604 observable reflections (I >2σ(I)) were used for structure resolution and refinements to converge to finalR 1 = 0.0414,wR 2 = 0.0815. The result of structure determination shows that the compound contains octamolybdate possessing a novel structure type (named as ξ-isomer). The feature of ξ-[Mo8O26]4- is that it is composed of Mo6O6 ring and two MoO6 octahedral located at cap positions on opposite faces. The Mo6O6 ring contains two octahedral and four trigonal-bipyramidal MoVI atoms. Each ξ-[Mo8O26]4- unit is bonded with two [Ni(phen)2]2+ through terminal oxygen atoms of octahedral and neighbouring trigonal-bipyramidal Mo atom in the Mo6O6 ring. IR and UV-Vis spectra of the compound were measured and its electronic structure was studied by EHMO method.

Structural studies of single crystals La6NiSi2S14 and La6CoSi2S14 under high pressure

Abstract Crystal structures and lattice constants have been determined within the pressure range from 1 bar to 47.1 kbar for La 6 NiSi 2 S 14 and from 1 bar to 84.4 kbar for La 6 CoSi 2 S 14 using a Mao-Bell type diamond cell on a four-circle diffractometer. The compression of La 6 NiSi 2 S 14 is slightly anisotropic and La 6 NiSi 2 S 14 is compressed more easily than La 6 CoSi 2 S 14 . Bond distances and bond angles for both substances were calculated based on the refined atomic coordinates data. A phase transition was concluded to take place in the structure of single crystal La 6 CoSi 2 S 14 above 64 kbar.

EXPERIMENT TECHNIQUE RESEARCH OF SINGLE CRYSTAL X-RAY DIFFRACTION UNDER HIGH PRESSURE

We have set up the high pressure device used for single crystal X-ray diffraction, determined the X-ray absorption curve of the device on Nicolet four-circle diffractometer, established the data collection programme of a fixed φ scheme, and corrected the offsets of the optical centering of the crystal by using a reflection which is measured in eight different orientations. The mixture ratio of methanol: ethanol: water 16: 3: 1 was used as a pressure medium, high pressure calibration was based on the wavelength shift of the R_1 fluorescence line of ruby, and the pressure of 100 kbar was obtained.