Study of intermolecular interactions in a system for equilibrium catalytic transesterification of esters. 1. Reaction of boron,titanium, and arsenic butoxides with esters according to IR fourier spectroscopic data

IR spectroscopy was used to study solutions of esters of PhCOOR (R=Me, Bu, C₇H₁₅, (CH₂)₂OBu) in B(OBu)₃, Ti(OBu)₄, and As(OBu)₃ and in mixtures of the latter with CCl₄ and hexane. It is shown that weak complexes form between the ester molecules and B(OBu)₃ and Ti(OBu)₄, As(OBu)₃ behaves with respect to the esters as a nonpolar solvent. Intermolecular interaction of the esters with butoxides occurs at the alkoxide oxygen in the ester. A mechanism of the exchange of the alkoxyl radical in the reaction of Ti(OBu)₄ with PhCOOMe is proposed on the basis of kinetic measurements.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 1991–1995, September, 1990.     

The infrared spectra (600-140 cm−1 of the imidazole,pyrazine and pyrimidine adducts of cobalt(II), nickel(II) and zinc(II) acetylacetonates

Summary The complexes M(acac)₂(imidazole)₂ (M = Co or NO and [M(acac)₂B]_n (M = Co, Ni or Zn; B = pyrazine or pyrimidine) have been prepared and their i.r. spectra determined over the 600–140 cm^–1. range. The metal-oxygen and metal-nitrogen stretching frequencies, (M-O) and v(M-N), are assigned on the basis of the band shifts induced by deuteriation of the adducted base and by substitution of the metal ion. Three or fourv(M-O) bands are observed within the 600-200 cm^–1 range. The twov(M-O) bands of higher frequency are considered to the coupled with internal ligand modes. TwovM-N) bands are observed within the 280–170 cm^–1. range. The metal-ligand stretching frequencies are in good agreement with the values previously established for these vibrations in the [M(imidazole)₆]²⁺ and Ni(acac)₂(pyridine)₂ complexes.     

Infrared studies of the effect of acetylene, hydrogen, and oxygen on CO adsorption on platinum hydrosols

Infrared spectra of CO-treated platinum hydrosols subsequently treated with acetylene, hydrogen, and oxygen reveal that v(CO)_ads decreases from 2070 cm⁻¹ with increasing gas-treatment time. This has been attributed to a reduction in the coverage of adsorbed CO. In Pt sol/CO/C₂H₂ systems, v(CO)_ads decreases to a limiting value of ca. 2060 cm⁻¹ after exposure to acetylene. In the Pt sol/CO/H₂ systems, v(CO)_ads decreases to ca. 2050 cm⁻¹ after exposure to hydrogen gas. The lower frequency in the Pt sol/CO/H₂ system has been attributed to CO adsorption on more active metal sites formed from the reduction of surface platinum oxides. Exposure of the CO-treated platinum hydrosols to O₂ gas was found to cause the eventual disappearance of the v(CO)_ads band in infrared spectra, which was attributed to oxidation of adsorbed CO to CO₂ by weakly bound surface layers of platinum oxides formed by the oxygen treatment.     

Vibrational frequencies and force constants of N2O4 in complexes with molecules of different solvents determined by Raman spectra andAb initio calculation

The Raman spectra of N₂O₄ solutions in organic solvents have been recorded. The frequencies ofv ₁,v ₂, andv ₃ bands of N₂O₄ increase with increasing solvent electron-donor properties. Especially large changes ofv ₃ N-N stretching band have been observed (254.5 cm^–1 in n-hexane, 276.5 cm^–1 in 1,4-dioxane). The ab initio calculations have shown that the interaction between N₂O₄ and electron-donor molecules causes an increase of N-N and N-O stretching and O-N-O bending force constants of N₂O₄ in agreement with the results of Raman study.     

Interaction of iron carbonyls with Lewis bases

The interaction of iron carbonyls Fe _n (CO) _m (wheren = 1,m = 5;n = 2,m = 9;n = 3,m = 12) with anionic Lewis bases (H^–, F^–, Cl^–, Br^– , I^–, CN^–, SCN^–, N₃ ^–, MeSO₃ ^–, MeCO₂ ^–, CF₃CO₂ ^–, S₂ ^–, CO₃ ^2–, and SO₄ ^2–) passes through two-stage redox-disproportionation. The first stage is the formation of an iron carbonyl-base complex, [Fe _n (CO) _m–1C(O)L]^–, and the second is a single-electron reduction of this complex by another molecule of the initial iron carbonyl, giving rise to Fe(l) and Fe(–l) derivatives.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 248–249, January, 1996.     

Structure and properties of furan-2-carboxylic acid esters. 1. Dipole moments and IR spectra

Dipole moment studies have revealed that furan-2-carboxylic acid esters exist in nonpolar solvents predominantly in O,O-cis-conformations. The dipole moment value of a 2-furoate ester depends on the electronic and steric effects of the substituents in the alcohol portion of the ester. The complex nature of the v _C=O band region in the IR spectra of 2-furoates is due primarily to the appearance of resonance absorption bands.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1605–1610, December, 1987.     

Synthesis and X-Ray Crystal Structures of Fe2Ru(CO)12−n (CNBu t ) n and FeRu2(CO)12−n (CNBu t ) n (n=1, 2)

The clusters Fe₂Ru(CO)_12–n (CNBu ^t ) _n (3, n=1; 4, n=2), FeRu₂(CO)_12–n (CNBu ^t ) _n (5, n=1, 6, n=2) and FeRu₂(CO)₁₁(CNCy) (5a) have been prepared by direct substitution from the parent carbonyl precursors Fe₂Ru(CO)₁₂ (1) and FeRu₂(CO)₁₂ (2). All compounds have been characterized spectroscopically and clusters 3, 4, 5, and 6 by single crystal X-ray determinations. In all cases, the isonitrile ligands adopt axial or pseudo-axial positions on a ruthenium atom. The structures of 3–5 are very similar to their parent clusters, but the extent of metal framework disorder is significantly less. Cluster 6 adopts the same C _2v Fe₃(CO)₁₂ type structure as 4, and thus differs markedly from the parent compound 2, which has a D ₃ structure .     

Electrochemical synthesis and magnetic studies of neutral transition metal imidazolates and pyrazolates

Summary The single-step electrochemical synthesis of neutral transition metal complexes of imidazole, pyrazole and their derivatives has been achieved at ambient temperature. The metal was oxidized in an Me₂CO solution of the diazole to yield complexes of the general formula: [M(Iz)₂] (where M = Co, Ni, Cu, Zn; Iz = imidazolate); [M(MeIz)₂] (where M = Co, Ni, Cu, Zn; MeIz = 4-methylimidazolate); [M(PrⁱIz)₂] (where M = Co, Ni, Cu, Zn; PrⁱIz = 2-isopropylimidazolate); [M(pyIz)_n] (where M = Co^III, Cu^II, Zn^II; pyIz = 2-(2-pyridyl)imidazolate); [M(Pz)_n] (where M = Co^III, Ni^II, Cu^II, Zn^II; Pz = pyrazolate); [M(ClPz)_n] and [M(IPz)_n] (where M = Co^III, Ni^II, Cu^II, Zn^II; ClPz = 4-chloropyrazolate; IPz = 4-iodopyrazolate); [M(Me₂Pz)_n] (where M = Co^II, Cu^I, Zn^II; Me₂Pz = 3,5-dimethylpyrazolate) and [M(BrMe₂Pz)_n] (where M = Co^II, Ni^II, Cu^I, Zn^II; BrMe₂Pz = 3,5-dimethyl-4-bromopyrazolate). Vibrational spectra verified the presence of the anionic diazole and electronic spectra confirmed the stereochemistry about the metal centre. Variable temperature (360-90 K) magnetic measurements of the cobalt and copper chelates revealed strong antiferromagnetic interaction between the metal ions in the lattice. Data for the copper complexes were fitted to a Heisenberg (S= ) model for an infinite one-dimensional linear chain, yielding best fit values of J=–62––65cm^–1 andg = 2.02–2.18. Data for the cobalt complexes were fitted to an Ising (S= ) model with J=–4.62––11.7cm^–1 andg = 2.06–2.49.     

IR spectroscopic study of thioacrolein and its photoisomerization to methylthioketene

The molecules of thioacrolein (1) and metylthioketene (3), which are labile under normal conditions, have been studied by the matrix Fourier transform infrared spectroscopy method. Compound1 was obtained by vacuum pyrolysis (1120 K, 10^–4 Torr) of diallyl sulfide. The analysis of its IR spectrum shows that1 exists as a mixture ofs-trans ands-cis conformers. UV irradiation ( > 248 nm) of matrix isolated1 results in a 1,3 hydrogen shift and the formation of3, which is characterized by a strong band of antisymmetric stretching vibrations of the thioketene fragmentvC=C=S at 1777.2 cm^–1. The experimental IR bands of molecules1 and3 were assigned to fundamental modes. The relatively low frequencies of the stretching vibrations of the double bonds (vC=C at 1598.0 cm^–1 andvC=S at 1071.8 cm^–1) and the heightened frequency of the C-C single bond stretching (vC-C 1173.7 cm^–1) in the spectrum of1 indicate appreciable delocalization of the electron density in the conjugated -orbital system.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 464–470, March, 1995.     

Cyclic ligands with fixed coordination geometry. Part 7 Cationic copper(I) complexes of composition [Cu(Vn3S3)L]+-CF3SO 3 - (Vn3S3=5,10, 15-trithia-cyclo-triveratrylene,L=CO,CH3OH)

Summary Copper(I) trifluoromethanesulphonate and 5, 10, 15-trithia-cyclo-triveratrylene (Vn₃S₃, 3) react with CO in CHCl₃ as solvent to yield a carbonyl complex which can be crystallised from EtOH in a CO atmosphere giving the complex [Cu(Vn₃S₃)(CO)]O₃SCF₃·0.5 EtOH (8), which was characterised by av(CO) absorption band at 2140 cm^–1 indicating a weak back donation of copper(I). When (8) is heated in MeOH in an N₂ atmosphere, complex [Cu(Vn₃S₃)(CH₃OH)]O₃SCF₃·MeOH (15) is formed. X-ray analysis of (15) reveals a distorted tetrahedral coordination of the copper(I) ion with a strongly bonded methanol ligand (Cu–O 198 pm, Cu–S 229 pm).     

Energy levels and crystal-field calculations of trivalent ytterbium in yttrium aluminum garnet and yttrium gallium garnet

The splitting of the two ² F states of Yb³⁺:YAlG and Yb³⁺:YGaG, have been determined from fluorescence and absorption spectra at low temperatures. The levels of the ground states of Yb³⁺: YAlG are at: 0, 388, 613, 778 cm^–1, those of Yb³⁺: YGaG at 0, 308, 567, and 672 cm^–1. Crystal field calculations yield the following values for Yb³⁺:YAlG; A ₂ ⁰ =270 cm^–1, A ₄ ⁰ =–165 cm^–1, A ₄ ⁴ =–1155 cm^–1, A ₀ ⁶ =21 cm^–1, A ₄ ⁶ =–304 cm^–1 and for Yb³⁺:YGaG: A ₀ ² =110 cm^–1, A ₀ ⁴ =–125 cm^–1, A ₄ ⁴ =–1250 cm^–1, A ₀ ⁶ =10 cm^–1 and A ₄ ⁶ =–142 ^–1 A satisfactory agreement has been found for calculated and observed splitting patterns.

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Zusammenfassung Die Aufspaltung der ² F-Zustände von Yb³⁺:YAlG(I) und Yb³⁺:YGaG (II) wurde bei tiefen Temperaturen aus Fluoreszenz- und Absorptionsspektren bestimmt. Die Niveaus des Grundzustandes von (I) liegen bei 0, 388, 613, 778 ^–1, die von (II) bei 0, 308, 567 und 672 ^–1. Die Ligandenfeldtheorie ergibt folgende Werte für die Kristallfeldparameter: für (I) A ₂ ⁰ =270 cm^–1, A ₄ ⁰ =–165 cm^–1, A ₄ ⁴ =–1155 cm^–1, A ₀ ⁶ =21 cm^–1, A ₄ ⁶ =–304 cm^–1 unf für (II) A ₀ ² =110 cm^–1, A ₀ ⁴ =–125 cm^–1, A ₄ ⁴ =–1250 cm^–1, A=10 cm^–1 and A ₄ ⁶ =–142 ^–1. Die Übereinstimmung zwischen berechneter und beobachteter Aufspaltung war befriedigend.

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Résumé La division, par le champ de ligandes, des états ² F _7/2 et ² F _5/2 dans Yb³⁺:YAlG et Yb³⁺:YGaG a été déterminée des spectres de fluorescence et d'absorption. Les sous-niveaux de l'état fordamental se situent à 0, 388, 613, 778 cm^–1 dans Yb³⁺:YAlG, à 0, 308, 567, 672 cm^–1 Yb³⁺: YGaG. Le calcul fournit les valeurs suivantes pour les paramètres: Yb³⁺: YAlG A ₂ ⁰ =270 cm^–1, A ₄ ⁰ =–165 cm^–1, A ₄ ⁴ =–1155 cm^–1, A ₀ ⁶ =21 cm^–1, A ₄ ⁶ = -304 cm^–1 Yb³⁺:YGaG: A ₀ ² =110 cm^–1, A ₀ ⁴ =–125 cm^–1, A ₄ ⁴ =–1250 cm^–1, A ₀ ⁶ =10 cm^–1 et A ₄ ⁶ =–142 ^–1. L'accord entre les spectres calculé et observé est satisfaisant.

     

The effect of carbonyl complexation on highly exothermic vanadium oxidation reactions

The effects of CO complexation on highly exothermic vanadium oxidation reactions is evaluated. We study the chemiluminescent (CL) reaction products formed when vanadium vapor entrained in Ar or CO is oxidized by O₃ or NO₂. The multiple collision V+Ar+O₃→VO^*(C ⁴Σ⁻, ⁴Φ, ²X)+Ar+O₂ reactive encounter yields two previously unreported VO excited states, whereas the V+Ar+NO₂→VO^*+Ar+NO reactive encounter populates states up to and including VO^* C ⁴Σ⁻. The multiple collision V+nCO+O₃ reactive encounter would appear to form a VOCO excited state complex, emitting in the region 420–560 nm, via the formation and oxidation of V(CO)₂ viz. V(CO)₂+O₃→VOCO^*+CO+O₂ and a relaxed VO excited state emitter via V+nCO+O₃→VO^*+nCO+O₂ where the VO excited state excitation is mediated by V–CO complexation. In complement, the much less exothermic V–NO₂ encounter displays an emission which, in concert with previous studies of CO complexation, suggests the formation of a VO(CO)₂ excited state complex viz. V(CO)₂+NO₂→VO(CO)₂^*+NO. The experiments characterizing CL are complemented by comparative laser-induced fluorescence studies of the VO X ⁴Σ⁻–CO and Ar interactions and their influence on the VO C ⁴Σ⁻–X ⁴Σ⁻ laser-induced excitation spectrum. These studies, in conjunction with further attempts to excite LIF in the 420–560 nm region, suggest that the observed complex emissions result primarily from VO excited state interactions. Complementary time-of-flight mass spectroscopy of vanadium and vanadium-oxide–carbonyl complex formation demonstrates the formation of V(CO), V(CO)₂, V₂(CO), and VOCO, the latter three of which demonstrate clear metastable-ion dissociation peaks for the processes VOCO⁺→V⁺+CO₂, V(CO)₂⁺→V⁺+2CO, and V₂(CO)⁺→V₂⁺+CO, suggesting that these vanadium complexes when formed in a reaction-based environment may be photodissociated with light in the visible and ultraviolet regions.     

Synthesis,stability and reactivity of cationic carbonyl complexes of rhodium(I)

Summary Trans-[RhCl(CO)L₂] (L = PPh₃, AsPh₃ or PCy₃) react with AgBF₄ in CH₂Cl₂ to give the novel species [Rh-(CO)L₂]⁺ [BF₄]^–.nCH₂Cl₂ (n = 1/2 or 1 1/2) (1–3), which we believe to be stabilised by weak solvent interaction. The corresponding stibine compound cannot be isolated by the same process, instead [Rh(CO)₂(SbPh₃)₃]⁺ [BF₄]^– (7) is formed when the reaction is carried out in the presence of CO. When reactions designed to prepare [Rh(CO)L₂]⁺ [BF₄]^– are performed in the presence of CO, or [Rh(CO)L₂]⁺ [BF₄]^– complexes are reacted with CO, [Rh(CO)₂L₂]⁺ [BF₄]^– (L = PPh₃, AsPh₃ or PCy₃) (4–6) are formed. If Me₂CO is used as solvent in the preparation of [Rh(CO)L₂]⁺ [BF₄]^– (L = PPh₃ or AsPh₃), then the products are the four-coordinate [Rh(CO)L₂-(Me₂CO)]⁺ [BF₄]^– (8,9) species. The complexes have been characterised by i.r., ³¹P and ¹H n.m.r. spectroscopy and elemental analyses.     

Vibrational energy storage in high pressure mixtures of diatomic molecules

CO/N₂, CO/Ar/O₂, and CO/N₂/O₂ gas mixtures are optically pumped using a continuous wave CO laser. Carbon monoxide molecules absorb the laser radiation and transfer energy to nitrogen and oxygen by vibration–vibration energy exchange. Infrared emission and spontaneous Raman spectroscopy are used for diagnostics of optically pumped gases. The experiments demonstrate that strong vibrational disequilibrium can be sustained in diatomic gas mixtures at pressures up to 1 atm, with only a few Watts laser power available. At these conditions, measured first level vibrational temperatures of diatomic species are in the range T_V=1900–2300 K for N₂, T_V=2600–3800 K for CO, and T_V=2200–2800 K for O₂. The translational–rotational temperature of the gases does not exceed T=700 K. Line-of-sight averaged CO vibrational level populations up to v=40 are inferred from infrared emission spectra. Vibrational level populations of CO (v=0–8), N₂ (v=0–4), and O₂ (v=0–8) near the axis of the focused CO laser beam are inferred from the Raman spectra of these species. The results demonstrate a possibility of sustaining stable nonequilibrium plasmas in atmospheric pressure air seeded with a few percent of carbon monoxide. The obtained experimental data are compared with modeling calculations that incorporate both major processes of molecular energy transfer and diffusion of vibrationally excited species across the spatially nonuniform excitation region, showing reasonably good agreement.     

Comparative FT infrared study of structural changes occuring on dealumination of zeolite Na-Y with ethylenediaminetetraacetic or hydrochloric acid

IR lattice vibration spectra were used to monitor the changes in the structure of zeolite Na-Y upon its dealumination with ethylenediaminetetraacetic acid (EDTA) or with HCl. The terminal Si-O(H,Na) bonds thus formed (which are detectable by characteristic absorbance at v 900–950 cm^–1) are energetically less uniform when EDTA has been used as the dealuminating agent. This inhomogeneity is connected with the local deformations of zeolite structure which result in lowering the symmetry of silicon-oxygen tetrahedra. As a consequence, two novel bands appear at v 1090 cm^–1 and 1200 cm^–1 in addition to the fundamental absorption bands, v_as (TO₄) (T = Si, Al), at 1030 cm^–1 and 1145 cm^–1. A mechanism of dealumination is proposed, which takes into account the topochemical peculiarities involved in the chelation of the framework aluminum ions with EDTA.Translated fromIzyestiya Akademii Nauk. Seriya Khimicheskay, No. 2, pp. 284–287, February, 1993.     

Spectroscopic and magnetic investigation of one uranium(IV)-polyoxotungstate complex

The polyoxotungstate K₁₉[U₂KAs₄W₄₀O₁₄₀]^.42H₂O was synthesized and investigated by spectroscopic and magnetic susceptibility measurements. The IR spectrum of the complex contains the n_as(U–O)»1133 cm^–1 band due to the uranium coordination at {AsW₉} units and WO₆ binding octahedra. Electronic spectra indicate a ³H₄ ground state for the uranium(IV) in a quasicubic configuration. ESR spectra show a small orthorhombic distortion from the cubic symmetry (g _x = 2.045, g _y = 2.050, g _z = 2.085, D = 18.31^.10^{–4 .}cm^–1, E = 5.99^.10^{–4 .}cm^–1). The uranium ions are antiferromagnetically coupled for T>200 K (m_eff = 1.3 m_B at room temperature).     

High resolution FT-IR spectrum of tricarbon bisulfide,SCCCS

The high resolution Fourier transform infrared spectra of thev ₄-v ₂ andv ₇ band systems of tricarbon disulfide, SCCCS, were measured with a Bomem D A3.002 interferometer and an apodized resolution of 0.004 cm^–1. The rotational structure of the bandsv ₄-v ₂, (v ₄+v ₇)–(v ₂+v ₇), (v ₄+2v ₇)–(v ₂+2v ₇) andv ₇ could be resolved and assigned. The analysis confirmed that SCCCS displays the dynamics of a linear molecule.     

Thermodynamics of complexation of lanthanides and some of transition metal ions by 5,5-dimethyl-cyclohexane-2-(2-hydroxyphenyl)-hydrazono-1,3-dione (DCPHD) and its derivatives

Summary Equilibrium betweenDCPHD,DC-4-Cl-PHD, andDC-4-Me-PHD and protons, transition, and lanthanide ions have been investigated at 30 °C by means of potentiometric titration in 75% (v/v) methanol-water mixture containing 0.10M KNO₃ as a constant ionic medium. Thermodynamic parameters (G, H and S) referring to the formation of species HL ^–,L ^––,ML ^+n–2 andML ₂ ^+n–4 (L ^–– denotes the ligand anion) have been determined in solutions. The solvent effects on the thermodynamic parameters of the complex formation are discussed in terms of differences in the donor ability of methanol and water solvents. The plots of thermodynamic parameters versus ionic potential (Z ²/r) of the lanthanide elements is not linear as expected from ionic theory. The obtained curve can be resolved in an initial group (the lighter lanthanides), an intermediate group (Sm-Dy), and a final group (the heavier ones, Tb-Lu). This behavior was explained in terms of differences in the dehydration of lighter lanthanide(III) from that of heavier ones.

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Thermodynamik der Komplexierung von Lanthaniden und einigen Übergangsmetall-Ionen mit 5,5-Dimethylcyclohexyl-2-(2-hydroxyphenyl)-hydrazono-1,3-dion (DCPHD) und seinen Derivaten

Zusammenfassung Die Gleichgewichte zwischenDCPHD,DC-4-Cl-PHD undDC-4-Me-PHD mit Protonen, Übergangsmetall- und Lanthaniden-Ionen wurden bei 30 °C mittels potentiometrischer Titration in 75% (v/v) Methanol-Wasser mit einem Gehalt an 0.10M KNO₃ als konstantem ionischem Medium untersucht. Die thermodynamischen Parameter G, H und S zur Bildung der Spezies HL ^–,L ^––,ML ^+n–2 undML ₂ ^+n–4 (L ^–– steht für das Ligandenanion) wurden in Lösung bestimmt. Die Lösungsmitteleffekte auf diese Komplexbildungsparameter werden auf Basis der Differenz im Donorvermögen von Methanol und Wasser als Solventien diskutiert. Die Diagramme der thermodynamischen Parameter gegen die ionischen Potentiale (Z ²/r) der Lanthaniden sind, wie nach der Ionentheorie zu erwarten, nicht linear. Die erhaltene Kurve läßt eine Anfangsgruppe (die leichteren Lanthaniden), eine mittlere Gruppe (Sm-Dy) und eine Endgruppe (die schwereren Lanthaniden. Tb-Lu) erkennen. Dieses Verhalten kann aus dem Unterschied im Dehydratationsverhalten erklärt werden.

     

Copper(I) complexes of neutral,deprotonated and protonated 4,6-dimethylpyrimidine-2 (1H)-thione

Summary The following copper(I) complexes of 4,6-dimethylpyrimidine-2(1H)-thione (HL), its protonated cation (H₂L⁺) and deprotonated anion (L^–) have been prepared: CuL, Cu(HL)X (X = Cl, Br or I), Cu(HL)₂X (X = C1 or Br), Cu₂(HL)₃Br₂, Cu(H₂L)X₂ (X = Cl or Br), Cu₃(HL)₂LA₂ (A = ClO₄ or BF₄ ). The i.r. spectra show that in all the HL and L^– complexes and in the Cu(H₂L)Br₂ complex, the ligands are S, N coordinated to the metal ion, while in Cu(H₂L)Cl₂ only the thiocarbonylic sulphur is coordinated, probably bridging two copper(I) atoms. Thev(CuN) (288–317 cm^–1 ) andv(CuS) (191–225 cm^–1 ) have uniform frequency values in all the complexes. The halide ions are, in all their complexes, wholly or in part coordinated giving twov(CuX) bands which may indicate an asymmetrical Cu-X Cu halide bridging bond.Author to whom all correspondence should be directed.     

Water in melts: Raman spectral investigation of the molten Ca(NO3)2·4H2O−KNO3 system

The Raman spectra of molten mixtures of Ca(NO₃)₂\4H₂O–KNO₃ have been examined, covering the concentration range of 0–70 mole% KNO₃. The frequencies in the spectra of the mixtures have been found to change slightly with concentration. Striking variations in the band shapes have been observed in the regions corresponding to the O–H stretching mode (2850–3850 cm^–1) and the v₄-NO ₃ ^– mode (700–750 cm^–). The results are discussed in terms of perturbed quasi-lattice structure for the melt, in which there could be a displacement of water molecules in the first coordination sphere around Ca²⁺ by the NO ₃ ^– ion.