Étude des isomères (CO)Fe(PF3)4

Assignments of a certain number of vibrational bands of (CO)Fe(PF₃)₄ are made with reference to the C_3v and C_2v isomers. A study of the Raman and spectra at low temperature revealed that in the solid state only one isomer exists. Furthermore, a comparative study of liquid (CO)Fe(PF₃)₄ and HCo(PF₃)₄ of molecular symmetry C_3v was made. These two approaches made it possible to determine the difference in enthalpy between the two isomers of the iron complex (+0-52±0.05 kcal.mole⁻¹) in the liquid state, as well as to verify the assignments proposed previously. The greater stability of the C_2v isomer is discussed.     

Etudes par spectroscopie dans l'ultra-violet et le visible, du fullerène C60 en solution dans le n-hexane ou adsorbé sur des solides diélectriques

Ultraviolet and visible spectroscopy studies of the fullerene C₆₀ melted in n-hexane or adsorbed on dielectric solids. Experiments of spectroscopy have been carried out, between the far ultraviolet and the near infrared, with pure C₆₀ or containing endohedral complexes rare gas atom-C₆₀, melted in n-hexane, and also pure C₆₀ adsorbed on surfaces of solids.Several phenomena have been observed: 1. a charge transfer due to the influence of interactions between the molecules of C₆₀ and surfaces of solids, yielding new transitions observed in the far ultraviolet ; and interpreted as super excited states of Rydberg type; 1.1. red and blue shifts for some transitions of adsorbed C₆₀, interpreted on the basis of attractive, or turned repulsive, dispersion forces; 1.1.1. emission processes for several transitions of adsorbed C₆₀, explained on the basis of a resonant coupling between these transitions and modes of the surface plasmon induced by the collective excitations of the C₆₀ molecule; this kind of process might be drawn to the Faraday instability in acoustics.     

Analyse en spectroscopie infrarouge, de la structure des complexes BF3 du méthanol, des méthanols deutériés et de l'acide acétique Comparaison de la liaison hydrogène et de la liaison donneur-accepteur

A study of the infrared spectra led to the conclusion that the 2-1 complexes formed from two molecules of methyl alcohol or acetic acid and one molecule of BF₃ have an open structure. One methyl alcohol molecule is linked by hydrogen bonding to a second molecule which is attached to BF₃. The consequences of the addition of BF₃ to the OH (OD) vibrators are similar to those of the formation of a hydrogen bond: elevation of the wave number of the in-plane bending vibration and lowering of the wave number of the stretching vibration compared with the monomer.     

Liaison hydrogène O-H-O symétrique : II. Spectres de vibration des oxalates acides de lithium hydratés et anhydres

Infrared and Raman spectra of polycrystalline LiHC₂O₄, LiHC₂O₄, · H₂O and their D and ⁶Li containing isotopic derivatives have been investigated at 300 and 90 K in the 4000–50 cm⁻¹ region. All the internal and external optically active modes of lithium hydrogen oxalate monohydrate have been identified and an assignment is given. The spectroscopic data are consistent with X-ray data showing an asymmetric short hydrogen bond with a positive deuterium isotope effect. The dehydration of LiHC₂O₄, · H₂O changes the type of hydrogen bond which becomes symmetric of the double minimum type. The deuteration of LiHC₂O₄, on the other hand. weakens the hydrogen bond and makes it asymmetric again. The asymmetry appears more pronounced at low temperature.     

Etude des propriétés de conduction électrique des polyphosphates: Li3Ba2(PO3)7, LiPb2(PO3)5, LiCs(PO3)2, et αLiK(PO3)2

The electrical conductivity of the crystallized polyphosphates Li₃Ba₂(PO₃)₇, LiPb₂(PO₃)₅, LiCs(PO₃)₂, and αLiK(PO₃)₂ has been determined at different temperatures by impedance spectroscopy. The conductivity, σ, spreads within a range of 1.59 × 10⁻⁸ to 1.79 × 10⁻⁷ S cm⁻¹ at 573 K, and from 1.71 × 10⁻⁵ to 9.86 × 10⁻⁴ S cm⁻¹ at 773 K. The transport should be assumed in the majority by the lithium ions with regard to the structural characteristics of these polyphosphates. The results are discussed and compared to the conductivity properties of other lithium ion conductors.     

Free electron model in cluster structure theory. Electronic structures of [Mo6S8(CN)6]6?, [Mo6Se8(CN)6]6?, [Re6S8(CN)6]4?, and Rh6(CO)16 clusters

The results of quantum chemical calculations of the electronic structure and geometry of octahedral clusters [Mo₆S₈(CN)₆]⁶⁻, [Mo₆Se₈(CN)₆]⁶⁻, [Re₆S₈(CN)₆]⁴⁻, and Rh₆(CO)₁₆ by the ab initio SCF (RHF) and DFT (B3LYP) methods with various basis sets are presented. The electronic states of the clusters under study in ideal spherically symmetric potential were classified in the orbital quantum number l (1s, 1p, 1d, 1f, 1g, 1h, 1i), l = 0–6. In real crystal field with O_h symmetry these states are split. The calculated new electronic states were matched to the irreducible representations of the point symmetry group O_h. The polarizabilities of the compounds considered are 55–65 ų. A new model for the electronic structure of octahedral clusters containing M₆ groups was proposed. The model is based on the idea of free electrons moving in spherically symmetric potential field. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2617–2624, December, 2005.     

Utilisation des ligands aminophosphinephosphinites en hydroformylation catalysée par le rhodium: amélioration de l'énantioselectivité par synthèse selective des hydrures RhH(CO)2L2

Asymmetric hydroformylation of styrene by rhodium catalysts modified with aminophosphinephosphinite ligands has been studied. Use of either Rh₄(CO)₁₂/L₂ mixture or RhClCOL₂ in electroreduction under CO/H₂, gives interesting results in respect of regio- (PhCHMeCHO/PHCH₂CH₂CHO) and enantio-selectivity when the ligands (1R,2S)-PPh₂NMeCHMeCHPhOPPh₂ and (CH₃)₂C(N(Me)PPh₂)-HCH₂OPPH₂ (e.e. > 30%) are used.

¹H and ³¹P NMR spectroscopy has indicated the occurrence of the RhH(CO)₂L₂ hydride precursor, suggested to be responsible for catalysis. It is a trigonal complex having an aminophosphine function in a trans position to the hydrogen, the equatorial position being occupied by the (P---O) group and the two CO moieties.     

Analyse des sites de KLu3F10 et BaCaLu2F10 par spectroscopie de l'ion Eu3+

The Eu³⁺ ion is used as a structural probe, in order to state precisely the symmetry at the different cationic sites in the KLu₃F₁₀ and BaCaLu₂F₁₀ compounds. The emission and excitation spectra recorded at 4.4, 77, and 295°K are analyzed and the experimental data for both systems are compared. The energy levels of the Eu³⁺ ion in KLu₃F₁₀ are given. It is shown that Eu³⁺ ions enter three different sites in BaCaLu₂F₁₀. The nature of these sites is discussed.     

Gezielte synthesen von zweifach μ3-verbrückten dreikernigen eisenclustern Fe3(CO)9(μ3-S)(μ3-X) (X = PR,AsR, SO) aus [Fe3(CO)9(μ3-S-t-C4H9)]−

The cluster anion [Fe₃(CO)₉(μ₃-S-t-C₄H₉)]^?, which is easily obtained by deprotonation from the cluster compound Fe₃(CO)₉(μ₂-H)(μ₃-S-t-C₄H₉), reacts with XCl₂ by elimination of t-C₄H₉Cl and Cl^? to give the clusters Fe₃(CO)₉(μ₃-S)(μ₃-X) (X = PR: I, X = AsR: II, X = SO: III), in which one edge of the iron triangle is opened. The μ₃-PR-bridged clusters I can also be obtained by reactions of SCl₂ with the anions [Fe₃(CO)₉(μ₃-PR)]^2?, prepared from Fe₃(CO)₉(μ₂-H)₂(μ₃-PR) by deprotonation. The geometry of I and II is exemplified by X-ray structure analyses. Experimental evidence for a reaction pathway, proposed for the high yield syntheses of I, is discussed.     

Etude des systèmes binaires formées par le chlorure de cyanogène et par les tétrachlorures de carbone,de silicium,de germanium et d'étain

Study of binary systems formed by cyanogen chloride and the tetrachlorides of carbon, silicon, germanium and tin. The diagrams of binary mixtures of cyanogene chloride with the tetrachlorides of carbon, silicon, germanium and tin were studied. Only SnCl₄ gives an addition compound: SnCl₄ · 2ClCN. The existence of the complex was confirmed by X-ray diffraction and vapour pressure measurements. This complex gives SnCl₄ · 2NOCl on treatment with nitrosyl chloride.     

An infrared and Raman spectroscopic study of the Hofmann-type complexes and clathrates: M(piperidine)2Ni(CN)4; M(piperidine)2Ni(CN)4·1.5G (M=Cd, Co, Ni or Cu; G=benzene)

New Hofmann-type complexes and clathrates of the forms M(piperidine)₂Ni(CN)₄ and M(piperidine)₂Ni(CN)₄·1.5G (M=Cd, Co, Ni or Cu; G=benzene) were prepared in powder form and their infrared and Raman spectra are reported. The spectral features suggest that these compounds are similar in structure to the Hofmann-type clathrates except for the copper compounds. The complex and clathrate of Cu have different spectral features in comparison with its analogues due to the Jahn-Teller effect.     

Étude infrarouge de complexes aldéhyde-trifluorure de bore Rôle des doublets libres de l'oxygène sur la vibration v(CH)ald

The infrared spectra of some aldehyde-BF₃ complexes were measured from 2.5 μ to 19 μ. The intensity and force constant of the v(CH)_ald range is dependent on the lone-pair electrons of the neighbouring oxygen atom. In the BF₃ complexes the intensity of v(CH)_ald is decreased and shifted 150 cm⁻¹ towards higher frequencies, while the band becomes simple. The addition of BF₃ is verified by checking the v(C=O) band, which is shifted 70 cm⁻¹ towards lower frequencies.     

紫外光激励产生高振动激发ν1模的NO2分子

The photon-excited NO2 at 308 nm has been investigated by Time-Resolved FTIR spectroscopy. The IR fluorescence from highly excited NO2(X2 A1) in ν1 vibrational mode has been observed. These excited states are resulted from the strong vibronic mixing of electronic excited A2 B2/B2 B1 states with the ground X2 A1 state. It is considered that symmetric stretching ν1 mode is reserved from the photolysis because its vibrational style is unsuitable for dissociation.     

Multiparameter equations of state for siloxanes: [(CH3)3-Si-O1/2]2-[O-Si-(CH3)2]i=1,…,3, and [O-Si-(CH3)2]6

This article presents the continuation of the work on the development of technical equations of state for linear and cyclic siloxanes already documented in this journal. The fluids considered herewith are octamethyltrisiloxane (MDM, C₈H₂₄Si₃O₂), decamethyltetrasiloxane (MD₂M, C₁₀H₃₀Si₄O₃), dodecamethylpentasiloxane (MD₃M, C₁₂H₃₆Si₅O₄), dodecamethylcyclohexasiloxane (D₆, C₁₂H₃₆Si₆O₆). The 12-parameter functional form proposed by Span and Wagner has been selected because of its positive characteristics. Siloxanes are produced in bulk quantities and are mostly utilized in the cosmetics industry and, mixed, as high-temperature heat transfer fluids. Furthermore, they are used as working fluids in high-temperature organic Rankine cycle power plants. The available property measurements are carefully evaluated and selected for the optimization of equation of state parameters. For some of the fluids, experimental values are scarce, therefore ad hoc estimation methods have been used to supply more information to the procedure for the optimization of the parameters of the equation of state. In addition, saturated liquid density and vapor pressure measurements are correlated with the equations proposed by Daubert and Wagner–Ambrose, respectively, to provide short, simple, and accurate equations for the computation of these properties. The recently developed isobaric ideal-gas heat capacity correlation for the selected siloxanes is included in the thermodynamic models. The performance of the newly developed equations of state is tested by comparison with experimental data and also with predictions calculated with the Peng–Robinson–Stryjek–Vera cubic EoS, as this model was adopted in previous technical studies. The new thermodynamic models perform significantly better than cubic equations of state. T–s and P  – v$v$ diagrams for all the substances are also reported.     

Synthesis and structural characterization of (μ-H)2RU3(CO)9(μ3-η-C8H12) and (μ-H)RU3(CO)9(μ3-η-C12H19)

The reaction between Ru₃(CO)₁₂ and a cyclic olefin (cis-cyclooctene or trans-cyclododecene) at 100 °C for several hours gives the title compounds (μ-H)₂RU₃(CO)₉(μ₃-η²-C₈H₁₂) (1), and (μ-H)RU₃(CO)₉(μ₃-η³-C₁₂H₁₉) (2), both of which have been characterized by X-ray diffraction studies, IR and NMR spectral measurements and elemental analysis. The prolonged reaction between Ru₃(CO)₁₂ and cis-cyclooctene gives compound HRu₃(CO)₉(C₈H₁₁) (3). Compound 3 has been characterized with IR and NMR spectral analyses. In 1 the cyclooctene ring is linked via a μ₃-η²-alkyne type of bonding to the face of the Ru₃ cluster. It is formally σ-bonded to two of the three Ru atoms and π-bonded to the third Ru. The two hydrides in 1 are bridging Ru---Ru bonds. In 2 the cyclododecene ring is bonded to the Ru₃ face via the μ₃-η³-CCHC linkage. There are two formal σ-bonds from the allyl part to the hydrido-bridged Ru atoms and the η³-allyl linkage to the third Ru atom.     

Reactions between 8-quinolinol (and related ligands) and triruthenium dodecacarbonyl; x-ray crystal structure determination of Ru3(CO)8(C9H6NO)2

8-Quinolinol reacts with Ru₃(CO)₁₂ to give Ru₃(CO)₈(C₉H₆NO)₂ and Ru- (CO)₂(C₉H₆NO)₂. A single-crystal X-ray study of the cluster compound shows that the three ruthenium atoms define an isosceles triangle, with two distances of 2.77 Å and one of 3.04 Å. Since both metalated oxygens act as three-electron donors (RuO distances 2.12 and 2.18 Å), the cluster is a fifty-electron species with a formal zero bond order for the elongated RuRu bond. Four other hydroxyhydrocarbylpyridine compounds also give complexes of composition Ru₃(CO)₈(L)₂ which probably have analogous structures.     

Phase transitions in A4Li(HSO4)3(SO4); A = Rb, K: Single crystal X-ray diffraction studies

The crystal structure of ferroelastic Rb₄Li(HSO₄)₃(SO₄) has been determined at two temperatures, which indicates a structural phase transition, tetragonal P4₃ witha = 7.629(1) ?,c = 29.497(2) ? at 293 K and monoclinic P2₁ witha = 7.583(3) ?,b = 29.230(19) ?,c = 7.536(5) ?,β = 90.14(1)° at 90 K. The crystal structure of K₄Li(HSO₄)₃(SO₄)₄ has also been determined at two temperatures, tetragonalP4₁ witha = 7.405(1) ?,c = 28.712(6) ? at 293 K and tetragonalP4₁ witha = 7.371(5) ?,c = 28.522(5) ? at 100 K. The overall coordination features in both the structures have been analysed in terms of bond valence sum calculations. Dedicated to Professor C N R Rao on his 70th birthday     

Reductive nitrosylation of tetraoxometallates—XVII. Molybdate-hydroxylamine-cyanide reaction, and synthesis and characterization of K2[Mo(NO)(CN)5] and (NMe4)2[Mo(NO)(CN)4]

A reaction condition is established which determines the nature of the products in the molybdate-hydroxylamine-cyanide reaction. With hydroxylamine always used in excess, it is the hydroxyl ion concentration of the reaction mixture which plays a vital role in determining whether K₄[Mo(NO)(CN)₅] or K₂[Mo(NO)(CN)₅] is obtained exclusively. The latter product is hereby reported for the first time. Its powder diffractogram being typical of a cubic system, a gross structural characterization has been made possible. The former under aqueous, aerobic conditions yields a new product, (NMe₄)₂[Mo(NO)(CN)₄].     

Perfluormethyl-element-liganden XIII [1]: ein neuer weg zu zweikernkomplexen des typs M2(CO)8E(CF3)2X (M = Mn,Re)

The reactions of M(CO)₅X ( M = Mn, Re; X = Cl, Br, I) with E₂(CF₃)₄ (E = P, As) between 50 and 90°C yield binuclear complexes of the type M₂(CO)₈E(CF₃)₂X with two different bridging ligands, the formation of which is influenced by M (Mn > Re), E (P > As) , and X(I > Br > Cl). The main by-product is the symmetrical system M₂(CO)₈[E(CF₃)₂]₂, which is however not formed by the partial replacement of X by E(CF₃)₂ since this reaction requires temperatures above 120°C. The observed products can be explained by a three-step reaction path starting with the cleavage of E₂(CF₃)₄ followed by the subtitution of a cis-CO group in the M(CO)₅X component by M(CO)₅E(CF₃)₂ and the ring closure.