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1.
Andrew L. Hector Marek Jura William Levason Gillian Reid Stuart D. Reid Michael Webster 《Acta Crystallographica. Section C, Structural Chemistry》2008,64(10):m321-m323
The title compounds, μ‐oxido‐bis[(tert‐butylselenolato)bis(η5‐cyclopentadienyl)niobium(IV)] toluene solvate, [Nb2(C5H5)4(C4H9Se)2O]·C7H8, and μ‐selenido‐bis[(tert‐butylselenolato)bis(η5‐cyclopentadienyl)niobium(IV)], [Nb2(C5H5)4(C4H9Se)2Se], consist of niobium(IV) centres each bonded to two η5‐coordinated cyclopentadienyl groups and one tert‐butylselenolate ligand and are the first organometallic niobium selenolates to be structurally characterized. A bridging oxide or selenide completes the niobium coordination spheres of the discrete dinuclear molecules. In the oxide, the O atom lies on an inversion centre, resulting in a linear Nb—O—Nb linkage, whereas the selenide has a bent bridging group [Nb—Se—Nb = 139.76 (2)°]. The difference is attributable to strong π bonding in the oxide case, although the effects on the Nb—C and Nb—SetBu bond lengths are small. 相似文献
2.
Arpita Datta Moumita Maiti Susanta Lahiri 《Journal of Radioanalytical and Nuclear Chemistry》2014,302(2):931-937
Separation of no-carrier-added (NCA) 97Ru from bulk niobium target has been carried out for the first time using green analytical technique, aqueous biphasic system. 50 % (w/v) polyethylene glycol (PEG)-4000, against 2 M solutions of various salts such as Na-citrate, Na-tartarate, Na-malonate, Na2CO3, NaHSO3, Na2SO4, Na2S2O3 K2HPO4, K3PO4, K2CO3 and 4 M KOH were employed at room temperature for the extraction of NCA 97Ru from bulk niobium. Influence of molecular weight of PEG rich phase as well as pH of some salt rich phase (e.g., Na-tartarate) on the extraction behaviour of NCA 97Ru into PEG rich phase was also observed. In the presence of sodium-tartarate salt solution, when volume of PEG-4000: Na-tartarate was 3:1, 91 % of NCA 97Ru was extracted into the PEG rich phase without any contamination of niobium target. Dialysis of PEG rich phase containing NCA 97Ru was carried out against deionised water to obtained pure NCA 97Ru. 相似文献
3.
《Journal of Inorganic and Nuclear Chemistry》1979,41(8):1193-1198
Extraction of niobium by tributyl phosphate (TBP) in the Purex process is inefficient; and in spite of this, niobium is found in solvent streams. Alternate mechanisms for niobium transfer into the solvent were sought. Butyl lauryl phosphoric acid (HBLP), a model compound of secondary degradation products of the solvent used in the process, was found to enhance niobium extraction above a threshold concentration of 5 × 10−4 M. A study of the niobium distribution coefficient dependences in the system HNO3-HBLP-dodecane on the HBLP, hydrogen ion and nitrate ion concentration suggests an extraction mechanism involving neutralization of an hydroxyl group bound to the niobium and no incorporation of nitrate into the extracted species. These results are supported by chemical analysis of the extracted species which show an empirical formula corresponding to Nb(OH)4BLP. Silica and zirconium monobutyl phosphate, under certain conditions, disperse adsorbed niobium in the solvent phase in the form of emulsions or suspensions. Centrifugation of these give no net enhancement of niobium transfer. 相似文献
4.
The IR spectra (3500—150 cm?1) of the complexes [M(aniline)2,X2 (M = Co, Ni, Cu, Zn; X = Cl, Br), [Zn(aniline)2I2] are discussed. Assignments of the internal ligand vibrations are based on the band shifts which result from 15N-labelling of the amino group. The metal—ligand stretching frequencies, ν(M—N) and ν(M—X), are assigned on the basis of the band shifts which occur on 15N-labelling and metal ion and halogen substitution. Two bands within the range 350–450 cm?1 are assigned to ν(M—N) while the ν(M—X) bands occur within the range 170–320 cm?1. The effects of structure and coordination number on ν(M—N) and ν(M—X) are discussed. The spectra of two ethanol adducts, [M(aniline)2-(ethanol)2Cl2] (M = Co, Ni) compared with those of the unsolvated species [M(aniline)2-Cl2], exhibit a unique band near 480 cm?1 which is insensitive to 15N-labelling and is assigned to ν(M—O). 相似文献
5.
O. A. Nikonova G. A. Seisenbaeva V. G. Kessler P. A. Shcheglov D. V. Drobot 《Russian Journal of Inorganic Chemistry》2007,52(11):1687-1693
Bimetal alkoxo complexes of rhenium, niobium, and tantalum with the general formula M4O2(OR)14(ReO4)2, where M = Nb or Ta and R = Me or Et, were prepared in ~80% yield by reacting niobium or tantalum alkoxide M(OR)5 (R = Me or Et) with rhenium heptoxide Re2O7 in toluene. Comparative analysis of the molecular structures of the complexes was carried out by means of single-crystal X-ray diffraction and IR spectroscopy. The effect of the organic ligand and crystallization temperature on the geometry of the perrhenate group was studied. The solubility of the aforementioned alkoxo complexes in organic solvents increases with increasing hydrocarbon chain length of the ligand. 相似文献
6.
The possibility of forming niobium oxynitride through the nitridation of niobium oxide films in molecular nitrogen by rapid
thermal processing (RTP) was investigated. Niobium films 200 and 500 nm thick were deposited via sputtering onto Si(100) wafers
covered with a thermally grown SiO2 layer 100 nm thick. These as-deposited films exhibited distinct texture effects. They were processed in two steps using an
RTP system. The as-deposited niobium films were first oxidized under an oxygen atmosphere at 450 °C for various periods of
time and subsequently nitridated under a nitrogen atmosphere at temperatures ranging from 600 to 1000 °C for 1 min. Investigations
of the oxidized films showed that samples where the start of niobium pentoxide formation was detected at the surface and the
film bulk still consisted of a substoichiometric NbOx phase exhibited distinctly lower surface roughness and microcrack densities than samples where complete oxidation of the
film to Nb2O5 had occurred. The niobium oxide phases formed at the Nb/substrate interface also showed distinct texture. Zones of niobium
oxide phases like NbO and NbO2, which did not exist in the initial oxidized films, were formed during the nitridation. This is attributed to a “snow-plough
effect” produced by the diffusion of nitrogen into the film, which pushes the oxygen deeper into the film bulk. These oxide
phases, in particular the NbO2 zone, act as barriers to the in-diffusion of nitrogen and also inhibit the outdiffusion of oxygen from the SiO2 substrate layer. Nitridation of the partially oxidized niobium films in molecular nitrogen leads to the formation of various
niobium oxide and nitride phases, but no indication of niobium oxynitride formation was found.
Figure Schematic representation of the phase distribution in 200 nm Nb film on SiO2/Si substrate after two steps annealing using an RTP system. The plot below represents the SIMS depth profiles of the nitridated
sample with the phase assignment 相似文献
7.
M. Ejaz 《Journal of Radioanalytical and Nuclear Chemistry》1975,27(1):67-75
The distribution of tantalum(V) between 0.1M trioctylamine oxide dissolved in xylene and sulphuric acid solutions has been studied. On the basis of results on the distribution, it is concluded that at sulphuric acid concentration 0.5M, tantalum is probably extracted by a solvate mechanism as the complex Ta(OH) (SO4)2·3TOAO. It has also been shown that tantalum can be quantitatively separated from niobium, uranium, thorium and rare earth elements by extraction with N-oxide of trioctylamine from 0.5M sulphuric acid solution. 相似文献
8.
Diantipyrylmethane is used for substoichiometric extraction of tantalum from 1—4M hydrofluoric acid into 1,2-dichlorethane. The selectivity of the method is good, niobium and antimony(V) being the main inteferences. The stoichiometric composition of the tantalum/diantipyrylmethane complex is 1:1. The method was usef for the determination of trace amounts of tantalum (0.52 ± 0.05 μ g?1) in a lake sediment (Bodensee/Lake Constance) by neutron activation/μ-spectrometry. Tantalum was determined in niobium samples by an isotope dilution procedure after separation of the matrix on a polyurethane foam column loaded with diantipyrylmethane. 相似文献
9.
The effect of zephiramine on the chelate formation and extraction of some divalent metals with oxine is reported. In the presence of zephiramine, the non-extractable 1:2 zinc— and cadmium—oxine chelates as well as the extractable 1:2 nickel— and manganese—oxine chelates become highly coordinated ternary complexes, M(Q)3 (zeph), which are easily extracted into 1,2-dichloroethane. Copper is easily extracted into 1,2-dichloroethane as Cu(Q)2, which is not affected by zephiramine. 相似文献
10.
Preparation, Characterization and Reaction Behaviour of Sodium and Potassium Hydridosilylamides R2(H)Si—N(M)R′ (M = Na, K) — Crystal Structure of [(Me3C)2(H)Si—N(K)SiMe3]2 · THF The alkali metal hydridosilylamides R2(H)Si—N(M)R′ 1a‐Na — 1d—Na and 1a‐K — 1d‐K ( a : R = Me, R′ = CMe3; b : R = Me, R′ = SiMe3; c : R = Me, R′ = Si(H)Me2; d : R = CMe3, R′= SiMe3) have been prepared by reaction of the corresponding hydridosilylamines 1a — 1d with alkali metal M (M = Na, K) in presence of styrene or with alkali metal hydrides MH (M = Na, K). With NaNH2 in toluene Me2(H)Si—NHCMe3 ( 1a ) reacted not under metalation but under nucleophilic substitution of the H(Si) atom to give Me2(NaNH)Si—NHCMe3 ( 5 ). In the reaction of Me2(H)Si—NHSiMe3 ( 1b ) with NaNH2 intoluene a mixture of Me2(NaNH)Si—NHSiMe3 and Me2(H)Si—N(Na)SiMe3 ( 1b‐Na ) was obtained. The hydridosilylamides have been characterized spectroscopically. The spectroscopic data of these amides and of the corresponding lithium derivatives are discussed. The 29Si‐NMR‐chemical shifts and the 29Si—1H coupling constants of homologous alkali metal hydridosilylamides R2(H)Si—N(M)R′ (M = Li, Na, K) are depending on the alkali metal. With increasing of the ionic character of the M—N bond M = K > Na > Li the 29Si‐NMR‐signals are shifted upfield and the 29Si—1H coupling constants except for compounds (Me3C)(H)Si—N(M)SiMe3 are decreased. The reaction behaviour of the amides 1a‐Na — 1c‐Na and 1a‐K — 1c‐K was investigated toward chlorotrimethylsilane in tetrahydrofuran (THF) and in n‐pentane. In THF the amides produced just like the analogous lithium amides the corresponding N‐silylation products Me2(H)Si—N(SiMe3)R′ ( 2a — 2c ) in high yields. The reaction of the sodium amides with chlorotrimethylsilane in nonpolar solvent n‐pentane produced from 1a‐Na the cyclodisilazane [Me2Si—NCMe3]2 ( 8a ), from 1b‐Na and 1‐Na mixtures of cyclodisilazane [Me2Si—NR′]2 ( 8b , 8c ) and N‐silylation product 2b , 2c . In contrast to 1b‐Na and 1c‐Na and to the analogous lithium amides the reaction of 1b‐K and 1c‐K with chlorotrimethylsilane afforded the N‐silylation products Me2(H)Si—N(SiMe3)R′ ( 2b , 2c ) in high yields. The amide [(Me3C)2(H)Si—N(K)SiMe3]2·THF ( 9 ) crystallizes in the space group C2/c with Z = 4. The central part of the molecule is a planar four‐membered K2N2 ring. One potassium atom is coordinated by two nitrogen atoms and the other one by two nitrogen atoms and one oxygen atom. Furthermore K···H(Si) and K···CH3 contacts exist in 9 . The K—N distances in the K2N2 ring differ marginally. 相似文献
11.
《Acta Crystallographica. Section C, Structural Chemistry》2017,73(11):930-936
The polyfluorinated title compounds, [M Cl2(C16H16F4N2O2)] or [4,4′‐(HCF2CH2OCH2)2‐2,2′‐bpy]M Cl2 [M = Pd, ( 1 ), and M = Pt, ( 2 )], have –C(Hα)2OC(Hβ)2CF2H side chains with H‐atom donors at the α and β sites. The structures of ( 1 ) and ( 2 ) are isomorphous, with the nearly planar (bpy)M Cl2 molecules stacked in columns. Within one column, π‐dimer pairs alternate between a π‐dimer pair reinforced with C—H…Cl hydrogen bonds (α,α) and a π‐dimer pair reinforced with C—Hβ…F(—C) interactions (abbreviated as C—Hβ…F—C,C—Hβ…F—C). The compounds [4,4′‐(CF3CH2OCH2)2‐2,2′‐bpy]M Cl2 [M = Pd, ( 3 ), and M = Pt, ( 4 )] have been reported to be isomorphous [Lu et al. (2012). J. Fluorine Chem. 137 , 54–56], yet with disorder in the fluorous regions. The molecules of ( 3 ) [or ( 4 )] also form similar stacks, but with alternating π‐dimer pairs between the (α,β; α,β) and (β,β) forms. Through (C—)H…Cl hydrogen‐bond interactions, one molecule of ( 1 ) [or ( 2 )] is expanded into an aggregate of two inversion‐related π‐dimer pairs, one pair in the (α,α) form and the other pair in the (C—Hβ…F—C,C—Hβ…F—C) form, with the plane normals making an interplanar angle of 58.24 (3)°. Due to the demands of maintaining a high coordination number around the metal‐bound Cl atoms in molecule ( 1 ) [or ( 2 )], the ponytails of molecule ( 1 ) [or ( 2 )] bend outward; in contrast, the ponytails of molecule ( 3 ) [or ( 4 )] bend inward. 相似文献
12.
Phenylarsonic acid permits satisfactory separation of niobium and tantalum and estimation of tantalum from an oxalate solution containing sulphuric acid up to pH 5.8. For complete precipitation of niobium the pH should exceed 4.8. In mixtures, tantalum is precipitated below pH 3.0 and niobium is then precipitated above pH 5.0. When the oxalate concentration is high, recovery of niobium with cupferron is recommended. When the ratio of Nb2O5, to Ta2O5 exceeds 2:1, reprecipitation of tantalum is necessary. The effect of interfering ions is studied. 相似文献
13.
A. Van Baalen C.J. Groenenboom H.J. De Liefde Meijer 《Journal of organometallic chemistry》1974,74(2):245-253
The synthesis and the properties of the complexes Cp2TaCl2, Cp2M(allyl), Cp2M(1-methylallyl) and Cp2M(2-methylallyl) with M Nb, Ta are described. The complex Cp2TaCl2 has one unpaired electron per tantalum atom, while the allyl complexes are diamagnetic. The IR and PMR spectra indicate that the allyl group is π-bonded to the metal. The mass spectra of the complexes are discussed; the thermal stability of the Cp2Nb- and Cp2Ta-(allyl) complexes was investigated by differential thermal analysis. The properties of the niobium and tantalum complexes are compared with those of the corresponding titanium complexes. 相似文献
14.
Peter G. Jones Ionel I. Mangalagiu 《Acta Crystallographica. Section C, Structural Chemistry》2009,65(6):o300-o302
Two polymorphs of the title compound [systematic name: 1‐(2,4‐dihydroxyphenyl)ethanone], C8H8O3, were investigated. The known structure [designated (I‐M); P21/c, Z = 4; previously investigated at room temperature by Robert, Moore, Eichhorn & Rillema (2007). Acta Cryst. E 63 , o4252] was redetermined at low temperature, and a new form [(I‐O); P212121, Z = 12] was discovered in the same sample. In both forms, the molecules are planar (apart from the methyl H atoms) and they contain intramolecular O—H...O=C hydrogen bonds. In polymorph (I‐M), molecules are linked into chains by a single intermolecular O—H...O hydrogen bond, and the chains are linked into sheets by two C—H...O hydrogen bonds. Three O—H...O hydrogen bonds link the molecules of polymorph (I‐O) into chains and neighbouring chains are connected by one C—H...O interaction to form an offset layer structure. Two weak methyl C—H...O interactions link the layers. 相似文献
15.
EHMO method has been used to calculate the electronic structure of PD2ML compounds (PD—pentadienyl or methyl-substituted one, M—transition metal atom, L—Lewis base). Compared with CP2M (CP—cyclopentadienyl), fragment orbitals of PD2M serve as starting point for general account of the effects of forming M—L bonds on configuration, conformation and stability of PD2-ML compounds. 相似文献
16.
Summary The reactions between niobium and tantalum pentachlorides and tri-t-butylphosphane and tricyclohexylphosphane under various reducing conditions (magnesium turnings, amalgamated magnesium or sodium naphthalenide) were investigated. The products are highly dependent on the experimental conditions. Niobium(IV) adducts: Nb2Cl8[P(Bu-t)3]2 and Nb2Cl8(PCy3)4 were obtained with magnesium turnings, while reduction to Ta2Cl6(PCy3)3 occurred under similar conditions with tantalum. Ligand exchanges from NbCl4(THF)2 also yielded niobium(IV) adducts Nb2Cl8(PR3)3. The formation of the first soluble diamagnetic niobium(IV) adducts appears to be favored by the strong basicity of PCy3 and P(Bu-t)3. However, these crowded niobium(IV) complexes are unstable both in the solid and in solution with respect to niobium(III). Derivatives in oxidation state 3: M2Cl6(PCy3)3 (M=Nb or Ta), Ta2Cl6[P(Bu-t)3]3 and Nb2Cl6[P(Bu-t)3]2 were formed more efficiently with amalgamated magnesium or with sodium naphthalenide. Activation of dinitrogen under mild conditions (normal pressure, room temperature) was observed during the reduction process with magnesium, for both tantalum and niobium; an unstable adduct, Nb2Cl6[P(Bu-t)3]3N2, could be isolated. All products were characterized by elemental analysis, magnetic susceptibility measurements and i.r. spectroscopy; their molecular structure is discussed in terms of the1H and31P n.m.r. data. 相似文献
17.
Jason W. Krizan Sergio H. Pulido Sarah E. Wehrhan Benny C. Chan 《Acta Crystallographica. Section C, Structural Chemistry》2010,66(7):i75-i78
The title compounds, namely hexacaesium tetraniobium docosaselenide and dodecapotassium hexaniobium pentatriacontaselenide, were formed from their respective alkali chalcogenide reactive flux and niobium metal. Both compounds fall into the larger family of solid‐state compounds that contain the M2Q11 building block (M = Nb, Ta; Q = Se, S), where the metal chalcogenide forms dimers of face‐shared pentagonal bipyramids. Cs6Nb4Se22 contains two Nb2Se11 building blocks linked by an Se—Se bond to form isolated Nb4Se22 tetrameric building blocks surrounded by caesium ions. K12Nb6Se35.3 contains similar Nb4Se22 tetramers that are linked by an Se—Se—Se unit to an Nb2Se11 dimer to form one‐dimensional anionic chains surrounded by potassium ions. Further crystallographic studies of K12Nb6Se35.3 demonstrate a new M2Se12 building block because of disorder between an Se2− site (85%) and an (Se—Se)2− unit (15%). The subtle differences between the structures are discussed. 相似文献
18.
Gregorio Guadalupe Carbajal Arizaga Jos Eduardo Ferreira da Costa Gardolinski Wido Herwig Schreiner Fernando Wypych 《Journal of colloid and interface science》2009,330(2):352-358
A Zn/Al layered double hydroxide with molar ratio of 3 was prepared by coprecipitation in alkaline pH and used as a matrix to intercalate the ionic complex diaquadioxalatooxoniobate(V) (DDON), derived from NH4[NbO(C2O4)2(H2O)2]2H2O. In a similar way, the layered zinc hydroxide nitrate, Zn5(OH)8(NO3)22H2O, was synthesized, preexpanded with azelate ions (−OOC(CH2)7COO−), and then intercalated with the niobium complex. For both layered matrices, the results from X-ray powder diffractometry, Fourier transform infrared spectroscopy, and thermal analysis (TG/s-DTA) indicate the presence of the oxalate ion. In addition, results from X-ray photoelectron and Raman spectroscopy indicate the presence of the niobium center bonded to oxygen atoms. Finally, diffuse reflectance UV–vis spectroscopy suggests that the niobium centers are coordinated to oxalate ions. This is the first report of the intercalation of niobium into a layered matrix. 相似文献
19.
Victor V. Kostjukov 《International journal of quantum chemistry》2024,124(3):e27349
This work is a development and extension of the previous one (DOI: 10.1039/d3cp00882g ). Here, H-dimers of acridine (acridine orange—AO and proflavine—PF), thiazine (methylene blue—MB and thionine—TH), and oxazine (brilliant cresyl blue—BCB and Nile blue—NB) dyes were modeled using hybrid functionals with a large proportion of exact Hartree–Fock exchange and long-range correction. It turned out that nine functionals (LC-ωHPBE, M06HF, M052X, M062X, M08HX, M11, MN15, SOGGA11X, and ωB97XD) reliably stabilize these molecular aggregates in both the ground and excited states. In addition, these functionals ensure that the conditions for transition moments (M(dimer) ≈ M(monomer) from strong coupling theory for H-aggregates) and absorption maxima (λmax(dimer) < λmax(monomer) from Kasha exciton theory) are met. The S2 excited state stabilizes the H-dimers more strongly than the ground state, while the S1 state stabilizes even more than S2. This is due to the large overlap between the corresponding molecular orbitals (LUMO > HOMO−1 > HOMO). When calculating the vibronic absorption spectra, the best agreement with the experiment for AO2, PF2, and NB2 showed the M08HX functional, and M11—for MB2 and BCB2. For dye monomers, these functionals gave the worst agreement, and MN15 demonstrated the closest similarity to the experiment. Vibronic absorption spectra for AO2, MB2, BCB2, and NB2 were calculated for the first time. The exciton splitting is calculated, which for MB2 is in good agreement with the experimental value. 相似文献
20.
The reduction of (η-C5H5)2NbCl2 (I) under various conditions gives the dimer (η-C5H5)4Nb2Cl3 (II) containing niobium(III) and niobium(IV). Reaction of II with AgClO4 gives [(η-C5H5)4Nb2Cl2]+ ClO4- (III). FeCl3 and (C6F5)2 TlBr displace I from II to give (η-C5H5)2Nb(μ-Cl)(μ-X)MY2, where MFe, XYCl(IV) and MTl, XBr, YC6F5 (V). Reactions of I with metal halides MXY2 give (η-C5H5)2ClNb(μ-Cl)MXY2 where XYCl, MAl (VI), Fe (VII), Tl (VIII) and XBr, YC6F5, MTl (IX). The chemical behaviour of all these compounds is described. 相似文献