Nanometer sized tantalum pentoxide fibers prepared by electrospinning
摘要:
Novel, porous tantalum pentoxide (Ta2O5) nanofibers with 150-250 nm diameter were obtained by high temperature calcination of the as-electrospun tantalum pentoxide/poly(vinyl acetate) (PVAc) composite fibers prepared by sol-gel processing and electrospinning technique. Surface analysis, structure and elemental composition of these as-electrospun and as-calcinated Ta2O5 nanofibers have been studied by scanning electron microscope (SEM) equipped with an energy dispersive X-ray analysis (EDX), high resolution field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), X-ray diffraction patterns (XRD) and FT-IR. High-resolution FE-SEM images showed the porous nature of Ta2O5 nanofibers. EDX analysis revealed the perfect stoichiometry of the nanofibers as Ta2O5. A linear correlation was noted between the calcination temperature and orthorhombic crystalline phase evolution of Ta2O5. (c) 2005 Elsevier Ltd. All rights reserved.
Synthesis and characterization of the first heteroleptic tin(II) isopropoxometallates
摘要:
Tin(II) isopropoxometallates of the types XSn{Al(OPr(i))4}, XSn{Zr2(OPri)9}, XSn{M(OPri)6}, {Al(OPri)4}Sn{Zr2(OPri)9} and {Nb(OPri)6}Sn{Ta(OPri)6} (where X = Cl, OPri/OBut; M = Nb/Ta) have been synthesized and characterized by elemental analyses, molecular weight measurements and multinuclear (H-1, C-13, Al-27 and Sn-119) NMR studies.
Oxidation Catalysis of Nb(salan) Complexes: Asymmetric Epoxidation of Allylic Alcohols Using Aqueous Hydrogen Peroxide as an Oxidant
作者:Hiromichi Egami、Takuya Oguma、Tsutomu Katsuki
DOI:10.1021/ja100795k
日期:2010.4.28
Several opticallyactive Nb(salan) complexes were synthesized, and their oxidation catalysis was examined. A dimeric mu-oxo Nb(salan) complex that was prepared from Nb(OiPr)(5) and a salan ligand was found to catalyze the asymmetric epoxidation of allylicalcohols using a urea-hydrogen peroxide adduct as an oxidant with good enantioselectivity. However, subsequent studies of the time course of this
合成了几种光学活性 Nb(salan) 配合物,并研究了它们的氧化催化作用。发现由 Nb(OiPr)(5) 和 salan 配体制备的二聚体 mu-oxo Nb(salan) 复合物可催化烯丙醇的不对称环氧化,使用尿素-过氧化氢加合物作为氧化剂,具有良好的对映选择性。然而,随后对该环氧化的时间过程以及配体的 ee 与产物的 ee 之间关系的研究表明,mu-氧代二聚体在环氧化之前解离成单体物质。而且,发现由 Nb(OiPr)(5) 和 salan 配体原位制备的单体 Nb(salan) 配合物,然后进行水处理,发现使用过氧化氢水溶液在 CHCl(3)/盐水或甲苯/盐水溶液中更好地催化烯丙醇的环氧化具有高对映选择性,范围从 83% 到 95% ee,除了肉桂醇的反应显示 74% 的中等 ee。这是使用过氧化氢水溶液作为氧化剂对烯丙醇进行高度对映选择性环氧化的第一个例子。
Synthesis of novel termetallic isopropoxides
作者:M. Aggrawal、R.C. Mehrotra
DOI:10.1016/s0277-5387(00)87035-7
日期:1985.1
i)2], [(PriO)2M(μ-OPri)2Be(μ-OPri)2Al(OPri)2]2 [whereM = Ti(IV), Zr(IV) and Hf(IV)] and [(PriO)4M(μ-OPri)2Be(μ-OPri)2Al(OPri)2] [whereM = Nb(V) and Ta(V)]. Attempts to synthesize derivatives with the general formula, [(PriO)7M2(μ-OPri)2Be(μ-OPri)2Al(OPri)2] [whereM = Ti(IV), Zr(IV) or Hf(IV)], were unsuccessful and in all such cases a mixture of M(OPri)4 and [(PriO)3M(μ-OPri)2Be(μ-OPri)2Al(OPri)2]
Molecular structure design and synthetic approaches to the heterometallic alkoxide complexes (soft chemistry approach to inorganic materials by the eyes of a crystallographer)
作者:Vadim G. Kessler
DOI:10.1039/b209168m
日期:2003.5.16
single source precursors of inorganic materials are demonstrated for such classes of compounds as oxoalkoxides, alkoxide beta-diketonates, alkoxide carboxylates, derivatives of functional alcohols, metallatranes and metallasiloxanes.
Interaction of some divalent metal acetylacetonates with Al, Ti, Nb and Ta isopropoxides. Factors influencing the formation and stability of heterometallic alkoxide complexesElectronic supplementary information (ESI) available: synthesis details for 5–7; microanalysis data for 1–9; tables of selected bond lengths and angles for 1–5 and 7–9; variable temperature 1H NMR spectra for 7 and 8; UV-Vis spectrum of 6 in toluene after various times. See http://www.rsc.org/suppdata/dt/b2/b206662a/
作者:Vadim G. Kessler、Suresh Gohil、Stephane Parola
DOI:10.1039/b206662a
日期:2003.2.11
(9), Al(OiPr)3 and Al(acac)3. Interaction of M(acac)2, (M = Co, Ni) with metal isopropoxides in iPrOH as well as their recrystallization from iPrOH give 2 and 9 respectively. 5–7 are unstable in the hydrocarbon solution on heating, decomposing with formation of [M2Al2(OiPr)6(acac)4], along with Al(acac)3 and heterometallic alkoxide species. Mg(acac)2 was found to recrystallize unchanged from the solutions
Co(acac)2与2 eq。的相互作用 Ti(O i Pr)4 in的数量正己烷导致新的异金属配合物[Co 2 Ti 2(acac)2(O i Pr)10 ](1)和已知的杂配醇盐Ti 2(acac)2(O i Pr)6的等摩尔混合物。当重新溶解在i PrOH 1中时,被破坏,形成[Co 2(acac)4(i PrOH)2 ](2)作为唯一可分离的结晶产物。Co(acac)2与3 eq。的反应 的Ta(O i Pr)5给出[Co2 Ta 2(O i Pr) 14 ]( 3)与Ta(acac)(O i Pr) 4一起。Ni(acac) 2与4 eq。的反应 Nb(O i Pr) 5的原子化产生异金属络合物[NiNb 2(O i Pr) 12 ]( 4)。M(acac) 2(M = Co,Ni,Mg和Zn)与Al(O i Pr) 3以1:2的比例反应可提供[MAl 2(O i Pr) 4(acac)
The solution thermolysis approach to molybdenum(V) alkoxides: synthesis, solid state and solution structures of the bimetallic alkoxides of molybdenum(V) and niobium(V), tantalum(V) and tungsten(VI)
作者:Anders Johansson、Magnus Roman、Gulaim A. Seisenbaeva、Lars Kloo、Zoltan Szabo、Vadim G. Kessler
DOI:10.1039/a907720k
日期:——
No complex formation can be observed between molybdenum(VI) oxoalkoxides and the alkoxides of niobium(V) or tantalum(V) at room temperature. The bimetallic derivatives of molybdenum(V), Mo4M2O8(OiPr)14, where M = Nb 1 and Ta 2, were instead isolated on cooling from the solutions of the isopropoxides in toluene subjected to a short-time reflux. The X-ray single crystal study showed both 1 and 2 to be
在室温下,未观察到钼(VI)的氧代醇盐和铌(V)或钽(V)的醇盐之间的络合物形成。取而代之的是从冷却条件下,从异丙醇溶液中分离出钼(V)的双金属衍生物Mo 4 M 2 O 8(O i Pr)14,其中M = Nb 1和Ta 2。甲苯短时间回流。X射线单晶研究表明二者1和2要建的(我PRO)3 M(μ-O我PR)3的MoO(μ-O)2的MoO(μ-O我PR)2的MoO(μ- O)2的MoO(μ-O我PR)3 M(0我PR)3与2的Mo-沫键(2.5836(8非直链分子)a)和短的但非粘合的Mo-M的距离(3.1791( 8)代表1)和3.1746(8)代表2)。根据核磁共振 和 EXAFS 数据,这种结构变得非常易变,甚至可能会部分分解为 烃解决方案。这氧化作用的2与氧引线的痕迹沫的形成3的Ta 2 ö 8(O我PR)10 3。可以从MoO(O i Pr)4与Ta(O i Pr)4(OMe)