Electrochemical synthesis of niobium compounds in anodic dissolution of ferroniobium in methanol
摘要:
Anodic dissolution of ferroniobium in anhydrous methanol in the presence of sodium methylate was studied. The possibility of recovering pure hexamethoxyniobate from the electrolyzate and its conversion into niobium methylate with an iron content not exceeding 0.01% was analyzed.
缩醛与碳亲核试剂的取代反应是基本的和常规的有机反应。我们成功地制备了旋光性缩醛,该缩醛与甲硅烷基烯醇醚平稳反应,得到所需外消旋形式的加合物。通过将产物的ee与回收的乙缩醛的ee进行比较,我们得出的结论是,醛醇型反应不是通过直接置换(S N 2)或接触离子对(亲密离子对)(S N 1)进行的。但由游离的氧碳鎓离子(S N1)机制。接下来,进行了研究以实现缩醛取代反应的不对称催化。经过多次试验,发现由五甲氧基铌[Nb(OMe)5 ]和四齿BINOL衍生物制备的手性铌络合物可以实现高对映选择性。缩醛与甲硅烷基烯醇醚的不对称醛醇型反应顺利进行,以高收率和高对映选择性提供了相应的醛醇型加合物。
Strategy to modify intrinsic luminescence via post-annealing treatment and impurity doping in SbNb3(PO4)6
作者:Suyin Zhang、Pengyue Zhang、Shan Tao、Xiaomei Zheng、Hyo Jin Seo
DOI:10.1016/j.jallcom.2020.156195
日期:2020.12
shows a broad self-activatedluminescence (400–750 nm) peaked at 485 nm. Impurity ion V5+ doping improves the intrinsic luminescence of SbNb3(PO4)6. The optimal efficiency of 31.63% was observed in 7.0 mol% V5+-doped SbNb3(PO4)6. Post-annealing of as-prepared SbNb3(PO4)6 in the air can enhance the luminescence, while, annealing in CO atmosphere deteriorates the intensity. The luminescence thermal stabilities
The formation of niobium and tantalum oxyalkoxide derivatives from niobium and tantalum alkoxides and alkoxychlorides
作者:L.G. Hubert-Pfalzgraf、J.G. Riess
DOI:10.1016/s0020-1693(00)89299-3
日期:1981.1
Abstract The niobium(V) and tantalum(V) oxyalkoxide derivatives NbO(OMe)2(OC6H4CHO), NbO(OMe)2[HB(pz)3] (pz = C3H3N2), NbOCl(OCH2CCl3)2· 2DMSO and TaOCl2(OMe)·2DMSO have been obtained from the pentaalkoxides or from the alkoxychlorides and characterized by microanalysis, molecular weight measurements, IR and NMR spectroscopy. The structure in solution of these oxo derivatives — all monomeric — which
Alkoxide hydrolysis as a route to early transition-metal polyoxometalates: synthesis and crystal structures of heteronuclear hexametalate derivatives
作者:William Clegg、Mark R. J. Elsegood、R. John Errington、Joanne Havelock
DOI:10.1039/dt9960000681
日期:——
Oxygen-17 NMR studies indicated that the hexametalates [MW5O19]n– or their derivatives [(MeO)MW5O18](n–1)–(M = Ti, Zr, V, Nb, Ta, Mo or W) can be obtained by hydrolysis of the appropriate mixture of metal alkoxides in the presence of M′O42–(M′= W or Mo) with remarkable selectivity in some cases, giving a very efficient method of preparing 17O-enriched polyoxometalates. The crystal structure of [NBun4]3[(MeO)TiW5O18]·0.5MeCN shows the terminal Ti–OMe bond in the anion to have Ti–O 1.760(10)Å and Ti–O–C 150.1(12)° and also reveals W–O bridging bond length alternations due to the substitution of Ti(OMe)3+ for WO4+ in the [W6O19]2– structure. Hydrolysis of [NBun4]2[(MeO)NbW5O18] gives [NBun4]4[(NbW5O18)2O] and the crystal structure revealed two eclipsed NbW5O18 oxide fragments joined by a strictly linear Nb–O–Nb linkage with Nb–O 2.264(8)Å.
Interaction of Co(acac)2 and Ta(OMe)5: isolation and single crystal study of the products. MII2MV2(acac)2(OMe)12, MII = Co, Ni, Zn or Mg and MV = Ta or Nb: A new class of heterometallic heteroleptic alkoxide complexes
作者:Pia Werndrup、Vadim G. Kessler
DOI:10.1039/b008526j
日期:——
The interaction of Co(acac)2 and Ta(OMe)5 in dry toluene led to formation of crystalline [Co2Ta2(acac)2(OMe)12] 1 and [Ta(acac)(OMe)4] 2 complexes. If the starting material is not completely water-free the products obtained are [Co4(acac)6(OMe)2(MeOH)2] 3 and Co(acac)2·2MeOH 4 due to hydrolysis of Ta(OMe)5 producing free methanol and thus altering the reaction pathway. The interaction of MII(acac)2, MII = Co, Ni, Zn or Mg, and MV(OMe)5, MV = Ta or Nb, in dry toluene was found generally to provide MII2MV2(acac)2(OMe)125–8, a new class of heterometallic heteroleptic alkoxide complexes. The crystal structures of 1–8 have been determined.