The structure of a 1:4 adduct between 1,4,7,10,13,16-hexaoxacyclooctadecane (18-crown-6) and thiourea

The structure of 18-crown-6·4 thiourea has been determined by single crystal X-ray methods. The unit cell is monoclinic and the space group isP2₁, witha=9.251(3),b=19.285(8),c=16.556(7) Å and =90.85(6)°. There are two formula units, C₁₂H₂₄O₆·4CH₄N₂S, in the asymmetric unit; finalR=0.086. One thiourea is attached at either side of the macrocycle (biangular conformation) via N–N...O bonds and the patterns in the two crystallographically-independent adductsA andB differ slightly, involving two bifurcated hydrogen bonds inA. Core adducts are linked by additional thiourea molecules via N–H...S bonds. As compared to the analogous 18-crown-6·5 urea, the present 1:4 stoichiometry might be attributed to the longer S...N hydrogen bonding distance, i.e., to the bigger van der Waals radius of sulphur. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82004 (31 pages). To obtain copies, see p. ii of this issue.     

Komplexe des zweiwertigen Molybdäns,Derivate des Oktahalodimolybdat(II)-Ions, 4. Mitt.: Darstellungen und Kristallstrukturen von zwei neutralen Komplexen mit 4-Methylpyridin

Mo₂Cl₄ Pic ₄·CHCl₃ (A) (Pic=4-methylpyridine) and Mo₂Br₄ Pic ₄ (B) crystallize in the monoclinic space group.A inC2/c (No. 15) witha=15.175 (4),b=10.847 (2),c=19.946 (6) and =104.52 (2)°;D _o=1.71 (2),D _c =1.72 gcm^–3 forZ=4.B inP2_l/n (No. 14) witha=9.270 (3),b=16.614 (5),c=9.305 (3) and =91.96 (5)°;D _o=2.03 (3),D _c =2.05 gcm^–3 forZ=2.Two halogens and 4-methylpyridines of the MoX ₂ Pic ₂ group are in the trans position. Mo–Mo bond lengths are 2.153 96) forA and 2.150 92) forB. Both molecules are situated on the inversion center resulting in the eclipsed configuration of the ligands around the molybdenum pair. The structure ofB has been refined to the conventionalR factors of 0.08 and 0.098. Disorder on the part of 4-methylpyridines and chloroform molecules stopped the refinement ofA at the endR value of 0.175.Mean Mo–X and Mo–N bonding distances are 2.40 (2), 2.25 (5) forA and 2.53 (3), 2.25 (1) forB.

     

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.     

Struktur und Farbigkeit von P,P′-Tetra-t-butyl-und P,P′-Tetraphenyl-oxalsäurediphosphid und Derivaten

The unexpected violet colour of P,P-tetraphenyl-oxalic acid diphosphide (3) stimulated the synthesis of the following derivatives: P,P-tetra-t-butyl-oxalic acid diphosphide (2), N,P-tetraphenyl-oxalic acid amide phosphide (4) and P, -triphenyl-glyoxylic acid phosphide (5). The compounds could be prepared by the reaction of the corresponding acyl chlorides with diorganyl-(trimethylsilyl) phosphine; (organyl=t-butyl and phenyl). The electronic transitions of green-blue2 and red5 in the 450–700 nm region are discussed, also theirv C=O in the ir spectrum. These results are interpreted in connection with the molecule structures of2 and3 which have been determined by X-ray crystal structure analysis. In2 the framework P–C(O)–C(O)–P is only slightly distorted from a coplanartrans-position, in3 somewhat more. The bonds at P have the expected pyramidal arrangement. The direction of the lone pairs at the P-atoms, derived from this bond arrangement, is discussed with respect to the electronic transitions in acyl phosphides.

     

Electronic and magnetic structure of the polymeric system di-imidazolato iron(II)

The polymeric system di-imidazolato iron(II) is synthesized from the reaction of either ferrocene or cyclopentadienyl-irondicarbonyl with imidazole. From Mössbauer measurements in the temperature range 4.2 KT448 K we find two different iron sites in the compound, denoted byA andB, respectively with ratio [A]/[B] = 1.79±0.03. From the isomer shift values we conclude that both Fe ^A and Fe ^B are in the ferrous high-spin state. Below 13.95±0.10 K both subspectra are considerably broadened due to magnetic ordering. From the analysis of the magnetic spectra we derive for the main componentV _zz of the electric field gradient tensorV _zz ^A >0 andV _zz ^B <0. Additionally, we investigate the thermal decomposition of the compound by thermogravimetry in the temperature range 20 °CT 750 °C and by Mössbauer spectroscopy in the temperature range 20 °CT505 °C. The decomposition takes place in four steps. The first step between 20 °C and 190 °C is due to the loss of imidazole nonbonded to iron(II). Comparing the amount of iron with that of pure imidazolato iron(II) we find the formula FeIz₂+0.70 (±0.02) IzH, with Iz standing for doubly deprotonated and IzH for deprotonated imidazole. Step 2 (193 °C<T<235 °C) and step 3 (400 °C<T<500 °C) are found from both methods. Step 4 is above 500 °C. Heat treatment and vacuum conditions affect the thermal decomposition products.Isomer shifts ^A and ^B , and temperature dependent quadrupole splittings E _Q ^A and E _Q ^B are explained using a simple ligand field picture for orbital splittings and occupancies of quasi-tetrahedrally (A) and quasi-octahedrally (B) coordinated ferrous high-spin compounds. Using finally the experimental ratio [A]/[B] = 1.79 we derive for the over-all chemical formula (1.79 Fe ^A Iz_4/2+Fe ^B Iz_4/2+2 IzH) _n = (FeIz₂+0.71 Iz) _–n in agreement with the result which we derived from investigating the thermal decomposition of our compound.Supported by Deutsche Forschungsgemeinschaft     

Synthesis,complexing properties and molecular modelling of open chain receptors of barbiturates derived from 2,6-diamino pyridine

Three new derivatives of 2,6-diacyldiaminopyridine are reported. NMR shift titrations were performed in CDCl₃ with barbiturates. The diamide1 affords a greater complexation energy (–13.00 kJ mol^–1) with bemegride than the dithioamide2 (–9.15 kJ mol^–1). This result, unexpected on the basis of the proton acidities, is explained by the great torsion energy induced in2 by the bulky sulfur atom. Compounds3 and4 present unusual four and five H-bond features with barbital and relatively weak complexation energies (–9.53 and –16.34 kJ mol^–1, respectively). Molecular mechanics indicates that ligand4 displays a helical secondary structure which is disrupted by complexation. Calculations of the H-bond energies (E _calc.) of the intermolecular assemblies with barbital or phenobarbital and other host-guest complexes given in the literature give a good correlation (r=0.98) with experimental values: E _calc.=1.07 G _a–42.0. Limitations of this relation are discussed.     

Über die thermische Stabilität der Eta-Carbide

Zusammenfassung Das Auftreten von -Carbiden vom TypusA ₃B₃C,A ₂B₄C undA ₆B₆C (A=Fe, Co, Ni,B=Mo, W) wurde untersucht. Mit Ausnahme des Systems Fe–Mo–C konnten in allen Systemen -Carbide des TypsA ₆B₆C beobachtet werden. Im System Co–Mo–C ist die Phase Co₆Mo₆C oberhalb 1000° C thermisch nicht mehr stabil, sondern zerfällt in Co₃Mo₃C+-Phase (Co₇Mo₆). Im System Co–W–C treten im Temperaturbereich 1100–1350° C drei strukturell eng verwandte -Carbide der Zusammensetzungen CO₆W₆C, Co₃W₃C und Co₂W₄C auf. Unterhalb 1000° C ist Co₃W₃C nicht beständig und zerfällt in Co₆W₆C, WC und Kobalt. Isotherme Schnitte durch das System Co–W–C bei 1100° C und 1300° C werden entworfen.

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About the thermal stability of eta-carbides

The occurence of -carbides of typeA ₃B₃C,A ₂B₄C, andA ₆B₆C (A=Fe, Co, Ni), (B=Mo, W) has been investigated. With the exception of the system Fe–Mo–C the formation of a phaseA ₆B₆C could be observed in all systems. The phase Co₆Mo₆C is not stable at temperatures exceeding 1000°C, but undergoes a decomposition to Co₃Mo₃C and -phase (Co₇Mo₆). Three structurally related -phases are observed in the system Co–W–C in the temperature range 1100 to 1350° C: Co₆W₆C, Co₃W₃C, and Co₂W₄C. Below 1100° C the phase Co₃W₃C is unstable and decomposes, forming Co₆W₆C, WC, and Co. Isothermal sections of the systems Co–W–C are drawn for the temperatures 1100 and 1300° C.

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Herrn Prof. Dr.R. Kieffer zum 65. Geburtstag gewidmet.     

The phenomenon of conglomerate crystallization. XIX. Clavic dissymmetry in coordination compounds. XVII

[Co(NH₃)₄(oxalato)]NO₃·H₂O (1) crystallizes as a conglomerate in space groupP2₁2₁2₁ with unit cell constants ofa=7.944(3),b=9.904(11), andc=12.700(2) Å;V=999.15 ų;d(calc.;z=4)=1.968 g cm^–3. [Co(NH₃)₄(oxalato)]¦·H₂O (2) crystallizes in space groupP2₂/n with cell constants ofa=7.285(1),b=9.959(3),c=15.410(5) Å;=102.63(2)° andV=1090.98 ų; d(calc;z=4) = 2.192 g cm^–3. Data were collected over the ranges of 4°270° and 4°255°, respectively for compounds1 and2. This resulted in a total of 2515 and 2823 data for the solution and refinement of the structures of compounds1 and2, respectively. When the refinements converged, the finalR(F) andR _w (F) values were, respectively, 0.073 and 0.080 for1 and 0.0378 and 0.0353 for2.Since neither data set was sufficiently good to give a sensible set of positions for all of the hydrogens, the stereochemistry of the two cations could only be defined by the positions of the heavy atoms. In the absence of reliable amine hydrogen positions, N(amine)-O(nitrate and oxalate) distances were examined. Close N(amine)-O(nitrate and oxalate) contacts indicate the presence of a network of significant hydrogen bonds in1. The N-O distances for compound2 also show the presence of hydrogen bonding between the amines and the oxalate ligand and water; however, the bonds are not of the same magnitude as the interactions involving the nitrate oxygens in1. Despite the similarity between the cations of1 and2, the Co-N distances in the two do not exhibit the same pattern. In1, the Co-N distances for amines trans to one another are shorter than the Co-N distances for amines trans to oxalate oxygens; this effect is reversed in2.     

Pyrroles from ketoximes and acetylene. 11. Conformation of 1-vinylpyrroles from1H NMR data

A number of 1-vinylpyrroles were studied by PMR spectroscopy. Bulky substituents in the position of the pyrrole ring give rise to deshielding of h_b and a decrease in²J(H_A,H_B) and⁶J(H₃,H_B). The results were interpreted as a decrease in the p, conjugation in the N-vinyl group due to distortion of the coplanarity. The dihedral angle () between the planes of the pyrrole ring and the double bond was estimated (with an accuracy of ±5 °).See [10] for our previous communication [10].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 328–330, March, 1980     

Preparation ofN-chloroacetyl-N′-arylsulfonylureas and the crystal structure ofN-chloroacetyl-N′-(4-methylphenylsulfonyl)urea

Novel arylsulfonylureas were prepared by the reaction of chloroacetyl isocyanate with arylsulfamides. The structures of the compounds synthesized were determined by IR and¹H NMR spectra. An X-ray structural analysis ofN-chloroacetyl-N-(4-methylphenylsulfonyl)urea was carried out. It was found that the molecule has theanti-syn conformation stabilized by an intramolecular H-bond. In the crystal, the molecules are combined into centrosymmetrical dimers by intermolecular hydrogen bonds. The compounds considered exhibit moderate fungicide activity.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1786–1788, October, 1994.     

Bis[(1,2-bis(2-(o-hydroxyphenoxy)ethyloxy)ethane)-(isothiocyanato)potassium] [K2(NCS)2(C18H22O6)2]: Crystal and Molecular Structure

Complex of podand 1,2-bis(2-(o-hydroxyphenoxy)ethyloxy)ethane (L) with potassium thiocyanate, [K₂(NCS)₂L₂] (I) was synthesized and studied using X-ray diffraction analysis: space group P , a = 7.771 Å, b = 11.711 Å, c = 11.965 Å, = 72.22°, = 79.21°, = 89.07°, Z = 1. Structure I was solved by direct method and anisotropically refined by the full-matrix least-squares method to R = 0.040 for all 4370 independent reflections (CAD4 autodiffractometer, MoK ). Structure I contains [K(NCS)L] monomers of the host–guest type united into centrosymmetrical [K₂(NCS)₂L₂] dimers via two bridging OH groups (one group from two L podands). In the monomer, the L podand appears as though to envelope the octacoordinated K⁺ cation, whose the coordination polyhedron is a strongly distorted hexagonal bipyramid with all six oxygen atoms of the L podand in its base and the N atom of the SCN^– ligand and the O atom of one of OH group of the neighboring (in dimer) L podand at its axial vertices. Molecules of I in crystal are joined through the O–H···N hydrogen bonds to form broad infinite chains along the x-axis.     

Molecular Structure of an Isocytosine Analog: Combined X-ray Structural and Computational Study of 2-Diethylamino-6-methyl-5-n-propyl-4(3H)-pyrimidinone

The structure of 2-diethylamino-6-methyl-5-n-propyl-4(3H)-pyrimidinone has been studied by X-ray crystallography and quantum-chemical calculations. X-ray analysis established that 2-diethylamino-6-methyl-5-n-propyl-4(3H)-pyrimidinone exists exclusively as the lactam tautomer protonated at the N3 ring nitrogen in the solid state. Crystals of 2-diethylamino-6-methyl-5-n-propyl-4(3H)-pyrimidinone are monoclinic (space group P2₁/n); the unit-cell dimensions are: a = 11.0460(8) Å, b = 5.0064(4) Å, c = 22.8358(17) Å, = = 90°, = 90.521(1)°. In the crystal, molecules of 2-diethylamino-6-methyl-5-n-propyl-4(3H)-pyrimidinone are assembled in planar centrosymmetric dimers by strong resonance-assisted N—H···O intermolecular hydrogen bonds from the NH group of one molecule to the C=O of the adjacent molecule (N—H···O distance 2.804 Å). Bond distances and angles are generally similar to those reported for the corresponding tautomer of isocytosine and derivatives. Quantum-chemical calculations on 2-diethylamino-6-methyl-5-n-propyl-4(3H)-pyrimidinone are also reported in order to estimate the relative energies of the possible tautomeric forms; ab initio and DFT results predict the coexistence of the N3 and AH tautomers in the gas phase. There is excellent correspondence between the crystal and the HF/6-311G** or B3LYP/6-31G* calculated structures of the N3 lactam form; the largest deviations between the experimental and computed structures are mostly the effects of strong intermolecular H bonds in the crystal.     

Thermal decomposition of strained spiro(1-pyrazoline-3,1′-cyclopropanes)

Pyrolysis (320–370 °C) of polycyclic 1-pyrazolines1 and2, obtained by 1,3-dipolar cycloaddition of diazocyclopropane to 3,3-dimethylcyclopropene and spiro[2,3]hex-1-ene, yields complex mixtures of isomeric hydrocarbons, substituted methylenecyclopropanes being the main components. Pyrolysis of 6-ethenyl- (4) and 6-methoxy-6-methylcarbonyl-4,5-diazaspiro[2,4]hept-4-enes (6) at 310–320 °C proceeds more unambiguously to give vinyl- (18) and 1-methoxy-1-methylcarbonylspiropentanes (20) in 85 and 95 % yields with respect to the transformed pyrazolines. Dediazotization of pyrazoline3 obtained from diazocyclopropane and benzvalene requires more drastic conditions (–440 °C) and produces indane.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2203–2207, November, 1995.This study was financially supported by the Russian Foundation for Basic Research (Grant No. 94-03-08902).     

Stereochemie von Metallocenen, 43. Mitt.: Torsionsisomere Biphenyl-tricarbonylchrom-Komplexe: Darstellung,Konformationsanalyse und Kinetik der Interkonversion

Complexation of methyl 3-nitro-2-(o-tolyl)-benzoate (2, ano-trisubstituted biphenyl) with hexacarbonyl chromium gave the isomeric Cr(CO)₃ complexes3 and4 both existing as two torsional isomersa andb, as seen by nmr. For the main product3 the preferred conformations of the two torsional isomersa andb were deduced by the lanthanide induced shift (LIS) technique. The activation energy for the interconversion process could be determined from kinetic measurements and especially from¹H-nmr coalescence temperature of the methylsignals. The barrier of 91±1.5 kJ/mol (21.7±0.3 kcal/mol) in3 reflects the interaction of theo-H-atom of the benzene ring passing the Cr(CO)₃ moiety of the benchrotrene ring during the interconversion.A partial optical resolution of3 was achieved by asymmetric reduction with a chiral lithium-aluminium hydride yielding (+)-3 with [] _D ²⁰ +30° (benzene) and the levorotatory alcohol (–)-7.

42. Mitt.:K. Schlögl undR. Schölm, Mh. Chem.109, 1227 (1978).     

Crystalline host-guest complexes involving carboxylic acid hosts and a dimethyl sulphoxide guest. X-ray crystal structures of two inclusion species

The host compounds 2,2-binaphthyl-3,3-dicarboxylic acid (1) and 1,13–1-terphenyl-2,4,4-tricarboxylic acid (2) have been synthesized, and crystal structures of their inclusion compounds with DMSO {1a [1·DMSO(11)];2a [2·DMSO (12)]} have been determined from single crystal X-ray diffraction data. The crystals show monoclinic symmetry withZ=4 (P2₁/n for1a andP2₁/c for2a), with the unit cell dimensionsa=11.567(1),b=10.206(1),c=17.579(1) Å,=100.50(1)° for1a, anda=14.910(1),b=6.732(1),c=26.084(1) Å,=100.41(1)° for2a. The structural models were refined toR=0.032 with 3127 reflections for1a, andR=0.035 with 3175 observations for2a, collected atT=173(1) K. Both structures comprise a characteristic molecular recognition pattern for DMSO via strong (CO)O–HO(=S) hydrogen bonds and possible C–HO contacts, the latter ones from the guest methyl groups to the carbonyl oxygen of the host carboxyl groups. In the crystals H-bonded endless chains of alternating host and guest molecules are formed, which are held together by ordinary van der Waals' forces. Additionally, host2 binds a second DMSO molecule by a single (CO)O–HO(=S) bond.Supplementary Data relating to this article have been deposited with the British Library at Boston Spa, Wetherby, West Yorkshire, U.K., as Supplementary Publication No. SUP 82186 (9 pages)     

Reductivetrans-2,6-diallylation of pyridines with allylboranes. Synthesis oftrans- andcis-2,6-diallyl-1,2,5,6-tetrahydropyridines and their deuterated derivatives

The reductivetrans-2,6-diallylation of pyridines with triallyl- and allyl(dialkyl)boranes has been discovered. Heating (40–100 °C) of pyridine, deuteropyridine, or 3-bromopyridine complexes with triallylborane in the presence of alcohols (ROH or CH₃OD), water, or Et₂NH results in the respectivetrans-2,6-diaIlyl-1,2,5,6-tetrahydropyridines (2,3,22, or25) in 20–97 % yields. A preparative method for the isomerization oftrans-2,6-diallyl compounds2 and25 into the respectivecis-isomers4 and28 by heating them with triallyl- or allyl(dialkyl)boranes (125–150 °C) has been suggested. The hydrogenation oftrans- orcis-2,6-diallyl-1,2,5,6-tetrahydropyridines gavetrans- orcis-2,6-dipropylpiperidines, respectively. Thecis- andtrans-configurations of compounds2 and4 were established by analyzing the NMR spectra ofN-benzyl (7 and13) andN,N-dimethyl (6 and 14) derivatives of piperidine derivatives5 and8. A possible mechanism for the reductive diallylation of pyridines has been discussed.Translated fromIzyestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 693–704, April, 1994.This study was financially supported by the Russian Foundation for Basic Research (Project 93-03-18193).     

Autoassembly of cage structures

The molecular structure of 1,4-dimethyl-2,5-dioxabicyclo[2.2.2]octane-3,6-dione (1) has been determined by X-ray diffraction analysis. The skeleton of dilactone1 has a synchro(+,+,+)-twist conformation with dihedral angles =4.0° for the hydrocarbon bridge bonds and =4.4, 4.6° for the lactone bridge bonds.For the previous paper in the series see Ref. 1.Translated fromIzyestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1965–1968, November, 1994.This work was supported by the International Science Foundation (MCO 000), the Russian Foundation for Basic Research (project code 94-03-08730), and NATO (LG 921193).     

Application of gas chromatography to study the resistance of Si-C bonds toward sulfuric acid

Conclusions It was shown that the reaction gas chromatography method can be used to determine the rate constants for the cleavage of the Si-C bonds in-trialkylsilylpropionic acids under the influence of sulfuric acid. We determined the rate constants for the cleavage of the Si-C bonds in the -trimethylsilylpropionic and-dimethylbutylsilylpropionic acids under the influence of sulfuric acid.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 195–197, January, 1974.     

Photochemical properties and the structure of 6-methyl-2,4-diphenyl-1-(p-tolyl)pyrimidinium perchlorate and the product of its photocyclization

The structure and photochemical properties of 6-methyl-2,4-diphenyl-1-(p-tolyl)pyrimidinium perchlorate (1) and 4,8-dimethyl-2-phenylpyrimido[1,2-f]phenanthridinium (2) formed as a result of photocyclization of1 have been studied. The crystal structure of compound1 has been studied at –140 °C and 25 °C. In cation1, theN-tolyl substituent and -Ph ring are noncoplanar with the pyrimidinium fragment (the angles are 67.9° and 41.1°, respectively), while the angle between the -Ph ring and the pyrimidinium moiety is only 7.1° (–140 °C). The photocyclization product2 has a flattened structure.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1731–1735, September, 1995.This work was partly (studies performed at Scientific Research Institute of Physical and Organic Chemistry at Rostov State University) supported by the Science Foundation Russian Universities.     

Röntgenstrahlenbeugung bei hohen Temperaturen zur Untersuchung der thermischen Ausdehnung von MnSe und MnSe2

Zusammenfassung Durch Röntgenstrahlenbeugung mit Hilfe einer 190 mm Unicam-Hochtemperaturkamera wurde die thermische Ausdehnung von MnSe und MnSe₂ von Zimmertemperatur bis 710° bzw. 522° C untersucht. Der thermische Ausdehnungskoeffizient wurde aus den Meßdaten nach der Methode der kleinsten Fehlerquadrate erhalten und beträgt für MnSe: =24,5·10^–6°C^–1 (94–450° C) und =14,3·10^–6°C^–1 (450–710° C). Die Ausdehnung von MnSe₂ verläuft bis zum Bereich, in dem Zersetzung eintritt, linear. Die Methode der kleinsten Fehlerquadrate ergibt den Wert =20,0·10^–6°C^–1 (73–522° C).

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High temperature X-ray studies of the thermal expansion ofMnSe andMnSe ₂

The thermal expansion of MnSe and MnSe₂ has been studied above room temperature up to 710° and 522° C, resp., by X-ray diffraction techniques using a 190 mm Unicam high temperature camera. The thermal expansion coefficients, , obtained from a linear least-squares analysis of the data are for MnSe: =24.5·10^–6°C^–1 (94–450° C) and =14.3·10^–6°C^–1 (450–710° C). The expansion of MnSe₂ is linear up to the temperature range of decomposition. A least-squares analysis yields a value for of 20.0·10^–6°C^–1 (73–522° C).

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Mit 2 Abbildungen

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Herrn Prof.H. Nowotny gewidmet.