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1.
The addition of trimethylphosphane to five-membered metallacyclic vinylketone complexes of the type ArR) (I) (Ar = η5-aromatic ring system: C5H5, C5H4Me, C5Me5; R = Me, Et, n-Bu; M = Mo, W) in pentane solution results in the formation of the ylidic metallacyclopropane complexes ArH(COR)] (II). In these 1:1 adducts the three-membered ring is stabilized by an electron-donating phosphonium and an electron-attracting acyl substituent. The negative charge in the ylidic complexes II is localized on the central metal providing it with Lewis base properties. An extraordinary high electron density can be observed on the metal of the derivative C5H5H-(COMe)] (III) which is formed by a 1:2 addition of C5H5W(CO)(C2H2)-(COMe) and PMe3. The metallacyclopropane complexes II and III are characterized by IR, 1H NMR, 13C NMR, 31P NMR and mass spectroscopy. For C5H5H(COMe)], the results of an X-ray structure determination are presented. 相似文献
2.
Kenneth R. Seddon 《Journal of organometallic chemistry》1984,270(1):c31-c32
The preparation of the first mixed metal cyclometallated compounds [ClPtCl]n (R = H, Cl) are reported; they were made from monocyclopalladated [(AcO)PCH(p-RC6H4)]2 and PtCl42?. 相似文献
3.
D.A. Lemenovskii V.P. Fedin A.V. Aleksandrov Yu.L. Slovohotov Yu.T. Struchkov 《Journal of organometallic chemistry》1980,201(1):257-268
Electron-acceptor properties of bis-niobocenes (η5-C5H4Y)(H)b(H)(η5-C5H4Y) with X Y H and XY SiMe2OSiMe2have been investigated. Bis-niobocenes are shown to readily add two electrons forming stable salts of the corresponding dianions [(η5-C5H4Y)(H)Nb(η5 : η1- C5H3X)2Nb(H)(η5-C5H4Y)]2-. The surplus electrons can be removed to give quantitative regeneration of initial neutral bis-niobocenes. The crystal and molecular structure of the title compound has been determined; R 0.044, interatomic distance are Nb…Nb 3.93, NbH 1.62, average NbC(π) 2.36, NbC(σ) 2.31 Å, other distances correspond to the usually observed values. Unlike the neutral bis-niobocenes, there is no direct metalmetal bond in the dianionic structures. This conclusion is supported by electronic spectra of neutral and dianionic species. 相似文献
4.
Tetsurō Nakamura 《Journal of solid state chemistry》1981,38(2):229-238
The isothermal decomposition of any ternary oxide AxByOz on liberation of n moles of oxygen at a constant pressure is found to be driven by the mixing entropy ΔSm = ?nRln PO2 of the total entropy change ΔS = ΔS° + ΔSm. The stability of AxByOz towards isothermal decomposition into a biphasic solid mixture is derived from the equilibrium condition as functions of standard changes ΔH° and ΔS°. Assuming ΔS° = 44n and calculating ΔH° in terms of lattice energies U(ABO3) and U(A2O3), the stability of perovskites is given as a function of the ionic radius of the A3+ ion. The calculated stability agrees well with that observed. The effect of electronic entropy change ΔSe on ΔS° is demonstrated for AFeO3 (A = La, Sm, Dy). 相似文献
5.
The incongruent vaporization reactions of Ta2S and Ta6S have been investigated by mass-loss effusion in the temperature range 1576 to 1902 K. By extrapolation of PS(obs) to equilibrium the enthalpies of the reactions and Ta6S = 6 Ta(s) + S(g) were found to be and , respectively. Comparison between the above values, determined by a 2nd law treatment, and 3rd law values was used to derive fef (“free energy function”) values for Ta and S in the compounds. These postulated fef's, which apply only to the elements as present in the compounds measured, are compared to tabulated quantities for the pure solid elements to provide a criterion for 2nd and 3rd law evaluation. 相似文献
6.
Unstable transition metal compounds formed from hydridosilacyclobutanes are described: 1-methyl-1-silacyclobutane reacts with nonacarbonyldiiron to give the complexes [Fe(CO)4(H){H2}] and [(H)Me}(CO)4], and with bis(triphenylphosphine)(ethylene)platinum(0) to give [Pt(H)(PPh3)2{H2}]. 相似文献
7.
The amine substituted phosphines (C6H5)2PN(H)CH2CH3 and (C6H5)2PN(H)CH2C6H5 react with C5H5Fe(CO)2CH(C6H5) (OCH3) photolytically to give moderate yields of the four-membered chelate ring complexes C5H5H (C6H5)] and C5H5H(C6H5)], respectively. Photolysis of C5H5Fe(CO)2CH(C6H5) (OCH3) in the presence of (S)-(?)-diphenyl(1-phenylethylamino)phosphine leads to the isolation of C5H5Fe(CO)[(C6H5)2PNC(CH3) (C6H5)]CH2C6H5 which is proposed to arise from a formally 1,3-hydrogen shift rearrangement of an intermediate four-membered chelate ring complex. 相似文献
8.
Tetsurō Nakamura 《Journal of solid state chemistry》1981,36(2):234-240
The standard entropy change ΔS° for the reduction of nonmagnetic, nonconducting oxides, , has been estimated as a function of m, n, and temperature T from motional entropies of oxygen molecules and vibrational entropies of solid phases. An available formula of ΔS°calc = a · m + b · n with constant a and b based on effective Debye temperatures, θM = 165 K for M and θOX = 540 K for MmOn, agrees well with the observed ΔS°obs for M2O, MO, M2O3, MO2, M2O5, and MO3 in the temperature range T = 300 – 1300 K. Possible electronic entropy corrections are applied to ΔS°calc for M2O7 and MO4. 相似文献
9.
The cyclometallation of p-RC6H4CHNCH2C6H2, (R = H, Cl, NO2) by PdX2 (X = Cl, AcO) has been studied.In every case the cyclometallation occurs with formation of a five-membered ring containing the methine group. The structure of these compounds [CH2C6H5)]2, derived from 1H NMR spectra, are different from those reported previously. Reaction of these compounds with PEt3 gives the compounds [PdX(p-RC6H3CHNCH2C6H5)(PEt3)2] but with an excess of PPh3 only the complexes [CH2C6H5)(PPh3)] are formed. 相似文献
10.
A new hydrate of tungsten trioxide, has been obtained by hydrothermal treatment at 120°C of an aqueous suspension of either tungstic acid gel or crystallized dihydrate. This hydrate has been characterized by different methods. A crystallographic study was carried out from X-ray powder diffraction. The hydrate crystallizes in the orthorhombic system: a = 7.359(3) Å, b = 12.513(6) Å, c = 7.704(5) Å, Z = 12. The existence of structural relationships between the hydrate, , and the product of dehydration, hexagonal WO3, has permitted us to propose a structural model in agreement with the experimental data. must be regarded as an interesting compound because its dehydration leads to a new anhydrous tungsten trioxide, hexagonal WO3. 相似文献
11.
Determination of the vapour pressures of o-, m-, and p-dinitrobenzene by the torsion-effusion method
D. Ferro V. Piacente R. Gigli G. DAscenzo 《The Journal of chemical thermodynamics》1976,8(12):1137-1143
The vaporization of o-, m-, and p-dinitrobenzenes was investigated by means of the torsion-effusion method and the selected equations for vapour pressure p as a function of temperature T are: The sublimation enthalpies ΔHo(o-, 298.15 K) = (21.0 ± 0.5) kcalth mol?1, ΔHo(m-, 298.15 K) = (20.8 ± 0.2) kcalth mol?1, and ΔHo(p-, 298.15 K) = (23.0 ± 0.6) kcalth mol?1, are also derived by means of the second- and third-law treatments of the results. 相似文献
12.
Proton NMR relaxation times (T2T1, and T1?) and absorption spectra are reported for the compounds H1.71MoO3 (red monoclinic) and H0.36MoO3 (blue orthorhombic) in the temperature range 77 K < T < 450 K. Rigid lattice dipolar spectra show that both compounds contain proton pairs, as OH2 groups coordinated to Mo atoms in H1.71MoO3 and as pairs of OH groups in H0.36MoO3. The room temperature lineshape for H1.71MoO3 shows that the average chemical shielding tensor has a total anisotropy of 20.1 ppm. The relaxation measurements confirm that hydrogen diffusion occurs and give EA = 22 kJ mole?1 and for H1.71MoO3 and EA = 11 kJ mole?1 and for H0.36MoO3. 相似文献
13.
The standard enthalpy of formation of γ-UO3 has been critically assessed; the value ?(292.5 ± 0.2) kcalth mol?1 is suggested.The enthalpies of solution of β-UO3 and γ-UO3 in 3 M H2SO4 have been measured and used to derive: 相似文献
14.
Reaction of BaO, Nb2O5, and Nb in mole ratios of 2.4:1.6:1 in an evacuated silica capsule at 1250°C produces a mixture of at least two products, one of which has the probable composition . This compound has an hexagonal unit cell of dimensions a = 9,034 ± 0.004 Å, c = 27.81 ± 0.02 Å, probable space group . Its structure has been determined from 942 independent reflections collected by a counter technique and refined by least squares methods to a conventional R value of 0.062. The basic structure consists of strings of four NbO6 octahedra sharing opposite corners, each string joined to the next by edge sharing of the end octahedra, so that the c axis corresponds to the length of a strand of seven corner-linked octahedra. Chains of three such strands are formed by corner sharing between the strands. The chains in turn are joined by NbO6 octahedra and Si2O7 groups in which the SiOSi linkage is linear. Barium atoms are in sites between the chains coordinated by 13 oxygen atoms. A second site, 15 coordinated, probably has a small amount of barium as well; the fractional occupancy for barium in this site is 0.076. 相似文献
15.
Osmotic pressure measurements on polystyrene () in trans-decalin for concentrations up to 140 kg m?3 and from 20 to 40 are reported. The θ-temperature is 20.8 . The ratio where c+ is the concentration at which a homogeneous segment distribution is assumed to prevail, increases with temperature up to the plateau value of 0.7. From the temperature dependence of the osmotic pressure, the partial molar enthalpy. Δh1, and entropy, Δs1. of mixing are found to be positive. The solvent-solute interaction parameter increases linearly with concentration at all temperatures. 相似文献
16.
Reaction of [PdCl2(PBut2Ph)]2 with silver acetate gives the internally metalated complex [PButPh]2(μ-Cl)2. This reacts with TlC5H5 and LiC5Me5 with chloride-bridge cleavage to yield C5R5PPButPh (R = H, Me). The complex [PBut2]2(μ-Cl)2,prepared from [PdCl2(PBut3)]2 and CH3COOAg, is analogously converted into C5R5But2. The chloride complex C5H5Pd(PBut5Ph)CI does not eliminate HCl to form C5H5PButPh. 相似文献
17.
Z. Dobkowski 《European Polymer Journal》1984,20(4):399-403
Linear and branched bisphenol A polycarbonate (PC) samples were characterized by their average molecular weights, and , polydispersity degree , and branching degree gv. The weight fraction of microgel was also determined for branched samples. The samples were amorphized and densities were measured at 23°C to obtain the values of specific volume, vsp. The dependence of vsp on molecular characteristics is described by the multivariable power function , where Δvsp = vsp ? vsp,∞, and Asp, a, apx and ab are constants. It has been confirmed that a = ?1, apn = 0 and apw = 1. It has also been found that the branching exponent ab significantly depends on microgel content. The relationships found for PC should, in principle, be valid for other polymers. Examples based on literature data are given for linear polyethylene and polydimethylsiloxane. 相似文献
18.
If in a potentiometric titration each addition of reagent equals Δv and if the observed potential steps are, in decreasing order, ΔEm, ΔE1 and ΔE2, the ratio ρα = is formed; ραΔv is the difference between the equivalence point and the known volume of reagent next to it. Both an extraordinary increase in the precision and a valuable simplification of the analysis are obtained. For Q = < 2.5 or ρα < 0.25 this value is approximated; but in this case a new series with doubled intervals may be formed from the potential steps observed in which ρα is very near to 0.5, found hence absolutely accurate. 相似文献
19.
Calorimetric measurements of the enthalpy of solution of cesium chromate gave ΔHsoln = (7622 ± 24) calth mol?1 for a dilution of Cs2CrO4·21128H2O. This result, along with the enthalpy of dilution gave the standard enthalpy of solution, ΔHsolno = (7512 ± 31) calth mol?1, whence the standard enthalpy of formation, ΔHf0(Cs2CrO4, c, 298.15 K), was calculated to be ?(341.78 ± 0.46) kcalth mol?1. Recomputed thermodynamic data for the formation of the other alkali metal chromates have been tabulated. From their solubilities and enthalpies of solution, the standard entropies, S0(298 K), of BaCrO4 and PbCrO4 were estimated to be (38.9 ± 0.9) and (43.7 ± 1.2) calth K?1 mol?1, respectively. There is evidence that ΔHf0(SrCrO4, c, 298.15 K) may be in error. Thermochemical, solubility, and equilibrium data, have been combined to update the thermodynamic properties of the aqueous chromate (CrO42?), bichromate (HCrO4?), and dichromate (Cr2O72?) ions. The new values at 298.15 K are as follows:
CrO42?(aq) | (13.8 ± 0.5) | ?(210.93 ± 0.45) | ?(174.8 ± 0.5) |
HCrO4?(aq) | (46.6 ± 1.8) | ?(210.0 ± 0.7) | ?(183.7 ± 0.5) |
Cr2O72?(aq) | (67.4 ± 3.9) | ?(356.5 ± 1.5) | ?(312.8 ± 1.0) |