共查询到20条相似文献,搜索用时 15 毫秒
1.
Arne Almenningen Ellen Gard Arne Haaland Jon Brunvoll 《Journal of organometallic chemistry》1976,107(2):273-279
The molecular structure of (C5H5)2Co has been determined by gas phase electron diffraction. The best agreement between calculated and experimental intensity curves is obtained with a model with eclipsed C5H5 rings (symmetry D5h), but a model with staggered rings (symmetry D5d) cannot be ruled out. The mean CoC and CC bond distances are 2.119(3) Å and 1.429(2) Å respectively. The average angle between the CH bonds and the C5 ring is 2.1(0.8)°. The value obtained for the CC vibrational amplitude, l(CC) = 0.055(1) Å, is significantly larger than the amplitude calculated from a molecular force field and the corresponding amplitudes in (C5H5)2Fe and (C5H5)2Ni determined by electron diffraction, and confirms the presence of a dynamic Jahn—Teller effect of the magnitude calculated from ESR data. The average structure is compared with those of the metallocenes of the other first row transition elements. 相似文献
2.
The molecular geometry of perfluoro(methyloxirane) has been studied using gas-phase electron diffraction data, effective least-squares refinement of the structure being achieved with the aid of constraints to limit the number of variable parameters. With the CCF3 bond constrained to be 0.078 Å longer than the ring CC, the refined bond- length values CF (av.) = 1.323(2), CO (av.) = 1.410(8), and CC (ring) = 1.467(7) Å (g values, with e.s.d. in parentheses) were obtained; the angles between ring bonds and substituent CF bonds were CCF (av.) 121(1) and OCF (av.) 114(1)o, the corresponding parameters involving the bulkier CCF3 fragment being larger by 3o in each case [∠CCCF3 124(1)o∠OCCF3 117(2)o]. The remaining refined parameters were ∠CCF(of CF3) = 110.6(4)o and τ , a torsion angle defining the orientation of the CF bonds of the CF3 group with respect to ring bonds, = 29(2)o. Dependent bond angles possessed the values 62.7 (COC), 58.7 [OCC (ring)], 108.3 [FCF (CF3 group)], 114 [FCF (ring CF2)], and 111o (FCCF3). 相似文献
3.
At a temperature above 1173 K the spinel-type structure of CdHo2S4 becomes unstable and gradually transforms into a rocksalt-type structure. During transition both Cd2+ and Ho3+ cations shift. Electron diffraction patterns obtained during transition show that the Cd, which shifted from a tetrahedral to an octahedral site, distorts the sulfur lattice. This distortion becomes visible as a modulation of the sulfur matrix. The modulation originally occurs in many crystallographic directions, however, upon annealing the 〈111〉 direction becomes preferred. Small domains of the high-temperature structure of CdHo2S4 appear to occur also in samples that were annealed well below 1173 K for a long period. 相似文献
4.
The structure of (Ph3SiN)2C has been determined by single crystal X-ray diffraction. The structure was solved by direct methods and refined to R = 0.071 for 593 independent diffractometer data. The crystals are rhombohedral, R with a = b = c 18.201(20) Å, α = β = γ = 48.82(2)°, and Z = 4. The three crystallographically independent molecules each have linear SiNCNSi chains lying along the crystallographic threefold axes; in two of the molecules the central carbon atom lies on a centre of symmetry. Principal mean bond lengths and angles are: Si, 1.696(25); SiC, 1.846(20); NC, 1.164(30); CC, 1.387(14) Å; CSi, 108.2(6); and CSiC, 110.8(6)°. 相似文献
5.
The crystal and molecular structures of [tris(trimethylsilyl)silyl]pentacarbonylmanganese, (Me3Si)3SiMn(CO)5, have been determined from three-dimensional X-ray data obtained by counter methods. The compound crystallizes in space group P of the triclinic system, with two molecules in a unit cell of dimensions: a = 9.002(2), b = 9.655(2), c = 15.639(3) Å, α = 83.66(1), β = 105.65(1), γ = 114.61(1)°.The observed and calculated densities are 1.20 (±0.03) and 1.23 g-cm?3 respectively. Full-matrix least-squares refinement of the structure has led to a final value of the conventional R factor of 0.059 for the 818 independent reflections having F2 > 3σ(F2).The coordination geometry about the manganese atom is approximately octahedral and, about the silicon atom bonded to the manganese atom, tetrahedral.The relative orientations of carbonyl and trimethylsilyl groups, when viewed down the MnSi bond, appear consistent with minimization of energy due to nonbonded interactions.Two of the equatorial carbonyl groups are displaced out of the equatorial plane towards the silicon ligand by 6°. The SiMn bond is 2.564(6) Å long and has no multiple character. 相似文献
6.
M.Velazquez Rosenthal T.A. Skotheim A. Melo M.I. Florit M. Salmon 《Journal of Electroanalytical Chemistry》1985,185(2):297-303
Copolymers of pyrrole and N-(p-nitrophenyl)pyrrole have been synthesized electrochemically. Cyclic voltammetric studies show that the electroactivities of both nitrobenzene and polypyrrole are apparent in the copolymer. Growth of poly-N-(p-nitrophenyl)pyrrole films is self-limiting an stops at 200 to 300 nm. Copolymerization allows thick and freestanding films incorporating the nitrophenyl moiety to be grown. 相似文献
7.
Lutz Rösch 《Journal of organometallic chemistry》1976,121(2):C15-C17
Trimethylchlorosilane reacts with aluminum and lithium in the presence of mercury under formation of tetrakis(trimethylsilyl)lithiumalanate. 相似文献
8.
Marit Traetteberg 《Journal of Molecular Structure》1984,118(3-4):333-343
The C=C double bond length in bicyclopropylidene (1) was found to be 131.4(1) and 130.4(8) pm by electron diffraction at 20° and X-ray diffraction at −40°C respectively. This value is in remarkable agreement with that obtained by molecular mechanics calculations; it is significantly shorter than the double bond in normal olefins. 相似文献
9.
Carlo A. Ghilardi Paolo Innocenti Stefano Midollini Annabella Orlandini 《Journal of organometallic chemistry》1982,231(4):C78-C80
Sodium tetrahydroborate reacts with iron(II) tetrafluoroborate and 1,1,1-tris(diphenylphosphinomethyl)ethane (triphos) to give the complex (triphos)-FeH(BH4) whose molecular structure, determined from X-ray data consists of monomolecular units in which the iron atom is six-coordinated by the three phosphorus atoms of the ligand, two hydrogen atoms of the BH4 group, and a hydridic hydrogen atom. Variable temperature 31P NMR spectra reveal stereochemical non-rigidity of the complex in solution. 相似文献
10.
J. Paul Attfield Peter D. Battle Anthony K. Cheetham 《Journal of solid state chemistry》1985,57(3):357-361
Magnetic susceptibility measurements have shown that β-CrPO4 orders antiferromagnetically at 37 K, and the magnetic structure at 5 K has been determined from a fixed-wavelength powder neutron diffraction experiment. The magnetic structure consists of a cycloidal spiral of moments which propagates along [100] with a periodicity of 3.07 ± 0.03a0. The magnetic properties are compared to those of the isomorphic compounds CrVO4 and MnSO4. 相似文献
11.
The structure of cyclobutadienedicobalt hexacarbonyl, (C4H4)Co2(CO)6, has been determined by single crystal X-ray diffraction techniques with data gathered at ?35°C by counter methods. Crystals form as red prisms in orthorhombic space group Pnma, with lattice parameters (at ?35°C) a = 12.916(3), b = 10.353(2) and c = 9.118(3) Å for a unit cell with four molecules of (C4H4)Co2(CO)6. The molecules have rigorous Cs symmetry, with a π-cyclobutadiene ring bound to the Co atom of a Co(CO)2 moiety which, in turn, is linked to a Co(CO)4 fragment through the metal atoms. Apparently to decrease repulsion between the cyclobutadiene ring and the bulky Co(CO)4 group, the four-membered ring is tilted, and as a consequence the CoC4H4 interaction is unsymmetrical (CoC(ring) = 1.980(3) to 2.048(4) Å). Full-matrix least-squares refinement of the structure has converged with a R index (on |F|) of 0.027 for 1539 symmetry-independent reflections with Io > 2.0σ(Io) within the Mo-Kα shell defined by 4° < 2θ < 60°. 相似文献
12.
G. Del Piero G. Perego S. Cucinella M. Cesari A. Mazzei 《Journal of organometallic chemistry》1977,136(1):13-18
The crystall and molecular structures of (ClAlN-i-Pr)6 (I), and of (Me0.83H0.17AlN-i-Pr)6(MeAlN-i-Pr)6 have been determined by single crystal three-dimensional X-ray analysis. Block-matrix least-squares refinements led to conventional R factor of 0.039 for I and 0.037 for II. The compounds are isostructural, as the cage molecules consist of a prismatic hexagonal framework, (AlN)6, similar to that observed for the parent hydrogenated analogue (HAlN-i-Pr)6.Some differences in bond distances and angles are discussed, in connection with the different Al-bonded substituents. Crystal data: I, trigonal space group R; a = 17.083(2), c = 9.652(1); Z = 3; Dc 1.46 g cm?3; II, trigonal space group R, a = 17.378(3), c = 9.706(3) »; Z = 3; Dc 1.15 g cm?3. 相似文献
13.
The thermal decomposition of tetrakis(diethyldithiocarbamato)tin(IV) has been studied by TG/DTA, EGA and P/GC-MS techniques. From the P/GC-MS analysis, it is apparent that the denticity of the dithiocarbamate ligand influences the mechanism of decomposition. Initially, the monodentate ligands decompose by a radical mechanism to form tetraethylthiuramdisulphide which decomposes further into carbon disulphide and diethylamine. The intermediate formed, bis(diethydithiocarbamato)tin(II), decomposes in two different ways. The bidentate ligands decompose with the liberation of carbon disulphide and tetraethylthiourea, whereas the monodentate ligands, formed as a result of the high temperatures, decompose to produce S-ethyl N,N-diethyldithiocarbamate and ethylisothiocyanate. The overall thermal decomposition mechenism of tetrakis(diethyldithiocarbamato)tin(IV) is complex and the primary decomposition involved both ionic and radical recombination reactions. 相似文献
14.
James A.S. Howell Denis T. Dixon John C. Kola 《Journal of organometallic chemistry》1984,266(1):69-82
(η4-enone)Fe(CO)2L complexes (enone = benzylideneacetone, cinnamaldehyde; L = PPh3-xMex (x = 0–2), P(OPh)3) exist as interconverting isomeric mixtures in solution in which L occupies either the axial or basal position of a square pyramidal structure. The ratio of isomers is dependent on the steric properties of both L and the enone. 相似文献
15.
Arthur T. Hubbard Roy M. Ishikawa James Katekaru 《Journal of Electroanalytical Chemistry》1978,86(2):271-288
Low-energy electron diffraction patterns were obtained for Pt(100), Pt(111) and polycrystalline electrodes before and after exposure to aqueous 1 M H2SO4. Linear potential scan voltammograms were recorded. The results demonstrate that one of the principal peaks in the hydrogen region of the current-potential curves of polycrystalline Pt is assignable to Pt(100) and the other to Pt(111). The maximum amount of chemisorbed hydrogen corresponds to one hydrogen atom per surface Pt atom. The Pt(100)[1×1], Pt(111) and polycrystalline surfaces appear to withstand prolonged voltammetric characterization at potentials between ?0.2 and 1.2 V vs. a calomel reference. Variation of the voltammetric characteristics of hydrogen chemisorption with changes in the nature of the supporting electrolyte anion are described. 相似文献
16.
The P/GC—MS and TG/DTA analysis, in an inert atmosphere, of bis(diethyldithiocarbamato)diphenyl tin (IV) indicates that the thermal decomposition proceeds in two consecutive stages. Loss of the dithiocarbamate ligands and the phenyl groups occurs within the temperature range of 210–380°C leaving tin (II) sulphide as residue. The stability of the phenyl radical as a reactive intermediate, together with the unidentate bonding of the dithiocarbamate ligand, dramatically influence the major mode of thermal decomposition. 相似文献
17.
V.E. Zavodnik V.K. Belsky Yu.G. Galyametdinov 《Journal of organometallic chemistry》1982,226(1):41-46
In order to elucidate the influence of aryl or alkyl substituents on the nature of the ? bond, which controls the complexing properties of the substances (Alk)n(Ar)3-nAsS (n = 0–3), the X-ray investigation of (p-MeC6H4)Et3AsS (TDEAS) and Ph2EtAsS (DPEAS) has been carried out. It was shown that the bond length AsS in these compounds has intermediate values (2.0896 and 2.0812 Å) in respect to those previously found by us in Et3AsS and Ph3AsS (2.115 and 2.077 Å). This confirms the conclusion that the increase of the number of aryl substituents in tertiary arsine sulfides leads to a decrease of electron density on the As atom along with simultaneous strengthening of the π-interaction between As and S. 相似文献
18.
A.F.M.J. van der Ploeg G. van Koten K. Vrieze 《Journal of organometallic chemistry》1982,226(1):93-103
Complexes [{2,6-(Me2NCH2)2C6H3} (p-tolylNYNR)PtHgBrCl] (Y CH, N; R Me, Et, i-Pr) have been prepared by the reaction of [{2,6-(Me2NCH2)2C6H3}-PtBr] with [Hg(p-tolylNYNR)Cl]. Similar complexes were obtained, although in lower yields, from exchange reactions of [{2,6-(Me2NCH2)2C6H3} (RCO2)-PtHg(O2CR)Br] with p-tolylNNN(H)-p-tolyl and p-tolylNC(H)N(H)Et.The proposed structure for these heterodinuclear compounds involves a Pt-to-Hg donor bond which is bridged by a triazenido (Y N) or a formamidino (Y CH) group, the five-membered ring thus formed acting as a stabilizing factor. The absence of a subsequent electron transfer reaction is ascribed to the constraints of the terdentate 2,6-(Me2NCH2)2C6H3 ligand, which fixes the N-donor atoms in mutual trans-positions.The use of p-tolylNYNR, where R is an alkyl group, results in the formation of two isomers of [{2,6-(Me2NCH2)2C6H3} (p-tolylNYNR)PtHgBrCl] with p-tolyl-N and alkyl-N sites bonded either to Pt or Hg. The relative abundance of these isomers varies systematically with the nature of the group R. It is suggested that the ratio is determined during the formation of the complexes and that both steric and electronic factors are important. 相似文献
19.
Gianfranco Ciani Vincenzo G. Albano Attilio Immirzi 《Journal of organometallic chemistry》1976,121(2):237-248
The structure of the title compound, (NEt4)2[H4Re4(CO)15], is reported in two crystallographic modifications, I and II. Both forms axe monoclinic and the cell constants are as follows: I, a 11.355(2), b 21.204(4), c 17.416(3) Å, β 94.15(2)°, space group P21/c; II, a 21.831(4), b 17.584(3), c 11.446(2) Å, β 96.02(2)°, space group P21,/n. Two sets of 3042 (I) and 2870 (II) independent diffraction intensities, collected by counter methods, were used for the solution and refinement of the two structures. The final conventional R factors have values 5.5% (I) and 6.3% (II), respectively. The crystal packings are compared, showing different conformations of the (NEt4)+ cations. The anions contain a tetrametal cluster formed by an isosceles triangle plus an apically bound metal atom; the carbonyl groups are all terminally bonded to the rhenium atoms. Some differences, present both in the metal atom clusters and in the carbonyl dispositions, are discussed and compared with a third, previously reported, crystallographic modification of the same compound. 相似文献
20.
P.D. Battle A.K. Cheetham W.T.A. Harrison N.J. Pollard J. Faber 《Journal of solid state chemistry》1985,58(2):221-225
Magnetic susceptibility measurements have shown that Cr2(MoO4)3 orders magnetically at 42 K. Powder neutron diffraction experiments at 295 and 5 K indicate that Cr2(MoO4)3 is chemically and magnetically isostructural with the L-type ferrimagnet Fe2(MoO4)3, and has a magnetic moment of 2.5 ± 0.2 μB per cation at 5 K. The limitations imposed on powder neutron diffraction methods by particle-size effects are discussed. 相似文献