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1.
Sally Dixon 《Tetrahedron》2004,60(6):1401-1416
A wide range of carbenoids (1-lithio-1-halo species), including those with α-SiR3, OEt, SPh, SO2Ph, P(O)(OEt)2, and CN substituents, insert into 5-member zirconacycles (saturated and unsaturated, mono- and bi-cyclic) to afford functionalized 6-member zirconacycles. 1-Lithio-1-haloalkenes insert to afford 6-member zirconacycles with an alkylidene substituent next to the metal. Unexpected double insertion of some carbenoids, and evidence for endocylic β-hydride transfer processes provide additional mechanistic interest. 相似文献
2.
The behavior of zirconium atoms at the W(100) surface associated with oxygen adsorption at different sample temperatures has been studied by Auger electron spectroscopy (AES), ion scattering spectroscopy (ISS), and the relative change of the work function (Δф) measured by the onset of the secondary electron energy distribution. The results have revealed: (i) adsorption of zirconium onto the W(100) surface followed by the elevation of the sample temperature up to 1710 K in an oxygen partial pressure of 2.7 × 10−4 induces complete diffusion of zirconium atoms into the W(100) substrate; (ii) further exposure of oxygen induces co-existence of oxygen and tungsten on the surface at 1710 K, resulting in a work function of 4.37 eV; (iii) keeping the sample temperature at 1710 K, simple evacuation of the system has resulted in surface segregation of zirconium atoms to the surface to form a zirconium atomic layer on the top-most surface, reducing the work function to 2.7 eV. The results have revealed that this specific behavior of zirconium atoms at high temperature assures, with very good reproducibility, the highly stable performance and long service life of Zr---O/W(100)-emitters in practical use, even in a low vacuum of 10−6 Pa. 相似文献
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The reactions of γ,γ-dialkoxyallylic zirconium species with carbonyl compounds in the presence of Lewis acid are reported. The reactivity of γ,γ-dialkoxyallylic zirconium species and reaction pathway were strongly dependent on the structure and electrostatic nature of the carbonyl compounds. 相似文献
5.
研究了四氧化锆作主催化剂的四元催化体系中,乙烯压力、催化剂浓度和温度对乙烯齐聚反应的影响.测定了稳定态下乙烯齐聚反应的宏观动力学方程和表观活化能. 相似文献
6.
LaB6-ZrB2共晶复合材料的组织特征及控制 总被引:2,自引:0,他引:2
用电弧炉和电子束悬浮区熔炉法制备了LaB6ZrB2共晶复合材料,并用SEM和TEM方法对其显微组织进行了研究。结果表明,LaB6ZrB2形成纤维状共晶组织,控制凝固条件可得到定向排列的组织,LaB6基体上均匀分布着直径为02~12μm的ZrB2纤维,纤维长度可达100μm以上。对于固液界面为平面生长的试样,其结晶学取向关系为[001]LaB6∥[001]ZrB2,(110)LaB6∥(010)ZrB2。 相似文献
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9.
Elke Barsties Stefan Schaible Marc-Heinrich Prosenc Ursula Rief Werner Rll Oliver Weyand Birgit Dorer Hans-Herbert Brintzinger 《Journal of organometallic chemistry》1996,520(1-2):63-68
Bis(2-N,N-dimethylamino-indenyl) zirconium dichloride, (2-(CH3)2N-C9H6)2ZrCl2, and dimethylsilyl-bridged bis(2-N,N-dimethylamino-indenyl) zirconium dichloride, (CH3)2Si(2-(CH3)2N-C9H5)2ZrCl2, were prepared by reaction of the corresponding ligand lithium salts with ZrCl4 in toluene. Diffractometric structure determinations reveal C2-symmetric complex geometries for both complexes. An increased electron density at the Zr center of the dimethylamino-substituted complexes is indicated by reduction potentials which are 0.3–0.4 V more negative than those of their unsubstituted analogs. When activated with methyl aluminoxane in toluene solution, (CH3)2Si(2-(CH3)2N-C9H5)2ZrCl2 catalyzes the polymerization of propene to polymers with a microstructure comparable with that of polymers produced with other Me2Si-bridged bis(indenyl)ZrCl2 complexes, but with a substantially increased fraction of i-propyl end groups derived from alkyl exchange between Zr-polymer and Al---Me species. 相似文献
10.
The reaction of [SiMe2(C5H4)2][(C5Me5)ZrMe2]2 with H2S at 110°C proceeds with the formation of [SiMe2(C5H4)2][(C5Me5)Zr(-S)]2]2. The molecular structure of this dinuclear zirconocenophane compound features a non-planar four-membered Zr2(-S)2
2 ring with two symmetrically-bridging sulfido groups. The bridging dimethylsilyl-bridged bis(cyclopentadienyl) ligand adopts a skewed orientation to accommodate the long Zr ... Zr separation of 3.611(1) Å. This compound crystallizes in the centrosymmetric space group P1 with refined lattice parameters ofa = 10.905(1) Å,b = 10.939(2) Å,c = 14.621(2) Å, = 106.32(1)°, = 91.25(1)°, = 111.25(1)°,V = 1545.1(8) Å3, calc. = 1.512g/cm3,Z=2. Full-matrix refinement converged with final discrepancy indices of R(F
o = 0.045 andR(F
o) = 0.079 with GOF= 1.60 for 4403 data withF
o > 3(F
o).This paper is dedicated to Professor Larry Dahl, a valued friend and mentor, on the occasion of his 65th birthday and in recognition of his significant fundamental contributions to the field of metal cluster chemistry. May the Goddess Fortuna continue to bring distinction and honor to him and his research endeavors. 相似文献