The twisted skeleton of 1,9-diaminononane incatena-[catena-,μ-(1,9-diaminononane)cadmium(II) tetra-μ -cyanonickelate(II)]-o-xylene(2/1)

The Hofmann-danon-typeo-xylene clathrate Cd[NH₂(CH₂)₉NH₂]Ni(CN)₄·0.5(CH₃)₂C₆H₄, crystallizes in the triclinic space groupP witha = 15.118(3),b = 14.048(4),c = 7.325(1) Å, = 91.50(2), = 131.66(3), and = 107.50(2)°,V = 1051(1) ų andZ = 2. The structure, refined toR = 0.047 using 2851 reflections, reveals a three-dimensional host framework built of the layers of a two-dimensionalcatena-[cadmium tetra--cyanonickelate(Il)] network and of the ambidentate 1,9-diaminononane (danon) bridging the Cd atoms in adjacent networks. The guesto-xylene molecule is accommodated in the cavity formed in the interlayer space similar to that in the Hofmann-daotn-type. The skeleton of the danon in the Cd-NC₉N-Cd linkage takes a (gauche)₂(trans)₈ conformation twisted at the (gauche)₂ part in contrast with the all-trans conformation of 1,8-diaminononane in the Hofmann-daotn-type clathrate. The twisted (gauche)₂ part of the danon skeleton occupies the interlayer space to such an extent that void space available for the guest o-xylene molecule decreases to half that in the Hofmann-daotn-type clathrate Cd[NH₂(CH₂)₈NH₂]Ni(CN)₄·G.The Crystal structures of ,-Diaminoalkanecadmium(II)Tetracyanonickelate(II) - Aromatic Molecule Inclusion Compounds. VI.     

Synthesis and properties of 2,2′-dipyridyl and 4,4′-dipyridyl complexes with thulium salts

Summary New complexes of 2,2-dipyridyl and 4,4-dipyridyl with thulium salts TmX ₃ (whereX=Cl^–, Br^–, NO ₃ ^– , NCS^–, and ClO ₄ ^– ) have been prepared and their solubilities in water at 21 °C were determined. The IR spectra of these compounds are discussed. The conditions of thermal decomposition of the complexes were also studied.

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Synthese und Eigenschaften von 2,2-Dipyridyl- und 4,4-Dipyridylkomplexen mit Thuliumsalzen

Zusammenfassung Es wurden neue 2,2-Dipyridyl- und 4,4-Dipyridyl-Komplexen mit Thuliumsalzen TmX ₃ (X=Cl^–, Br^– No ₃ ^– , NCS^–, ClO ₄ ^– ) dargestellt und ihre Wasserlöslihkeit bei 21 °C bestimmt. Die IR-Spektren werden diskutiert. Das thermische Verhalten der erhaltenen Komplexe wurde untersucht.

     

Neutral molecule/crown ether interactions 5. Comparison of the C−H acidic interactions of nitromethane and acetonitrile with 18-crown-6 and dibenzo-18-crown-6. Crystal structures of dibenzo-18-crown-6·2 CH3NO2 and dibenzo-18-crown-6·2 CH3CN

Complete structural characterization of dibenzo-18-crown-6·2 CH₃NO₂ and dibenzo-18-crown-6·2 CH₃CN have been carried out, including location and refinement of the methyl hydrogen atoms. Dibenzo-18-crown-6·2 CH₃NO₂ is monoclinic,P2₁/c, with (at –150°C)a=9.573(2),b=14.636(2),c=33.471(7) Å, =93.77(2)°, andD _calc=1.37 g cm^–3 forZ=8. Interactions between the solvent methyl groups and the crown ethers and other solvent nitro groups associate the 1 : 2 complexes into polymeric chains alongb. The acetonitrile adduct exists as discreet 1 : 2 complexes in the solid state with C–H...O interactions exlusively to the ether. This complex is triclinic,P 1, with (at –150°C)a=9.458(6),b=9.570(5),c=14.404(5) Å, =73.18(4), =79.85(5), =66.82(6)°, andD _calc=1.28 g cm^–3 forZ=2. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82070 (22 pages).For part 4, see reference [1].     

Dissociation quotients of oxalic acid in aqueous sodium chloride media to 175°C

The first and second molal dissociation quotients of oxalic acid were measured potentiometrically in a concentration cell fitted with hydrogen electrodes. The emf of oxalic acid-bioxalate solutions was measured relative to an HCl standard solution from 25 to 125°C over 25^o intervals at nine ionic strengths ranging from 0.1 to 5.0 molal (NaCl). The molal dissociation quotients and available literature data were treated in the all anionic form by a five-term equation that yielded the following thermodynamic quantities at infinite dilution and 25°C: logK_1a=–1.277±0.010, H _1a ^o =–4.1±1.1 kJ-mol^–1, S _1a ^o =38±4 J-K^–1-mol^–1, and C _p,1a ^o =–168±41 J-K^–1-mol^–1. Similar measurements of the bioxalate-oxalate system were made at 25^o intervals from 0 to 175°C at seven ionic strengths from 0.1 to 5.0m. A similar regression of the experimentally-derived and published equilibrium quotients using a seven-term equation yielded the following values at infinite dilution and 25°C: logK_2a=–4.275±0.006, H _2a ^o =–6.8±0.5 kJ-mol^–1, S _2a ^o =–105±2 J-K^–1-mol^–1, and C _p,2a ^o =–261±12 J-K^–1-mol^–1.     

Thermally induced isomerisation and decomposition of diethylenetriamine complexes of nickel(II) in the solid state

Summary Complexes [NiL₂]X₂·nH₂O (L=diethylenetriamine; n=O when X=CF₃CO₂ or CCl₃CO₂; n=1 when X=Cl or Br, and n=3 when X=0.5SO₄ or 0.5SeO₄) and NiLX₂·nH₂O (n=1 when X=Cl or Br; n=3 when X=0.5SO₄ or 0.5SeO₄) have been synthesised and investigated thermally in the solid state. NiLSO₄ was synthesised pyrolytically in the solid state from [NiL₂]SO₄·[NiL₂]X₂ (X=Cl or Br) undergo exothermic irreversible phase transitions (242–282° C and 207–228° C; H=–11.3 kJ mol^–1 and –1.9 kJ mol^–1 for [NiL₂]Cl₂ and [NiL₂]Br₂, respectively). [NiL₂]-phenomenon (158–185° C; H=2.0 kJ mol^–1). NiLX₂· nH₂O (n=1 or 3) undergo simultaneous deaquation-isomerisation upon heating. All the complexes possess octahedral geometry.     

Zur Bereehnung des Behinderungspotentials der inneren Rotation von Wasserstoffperoxid

Zesummenfassung Auf der Grundlage des Hellmann-Feynman-Theorems wird das Behinderungspotential der inneren Rotation von H₂0₂ berechnet unter Verwendung einer genäherten Elektronendichteverteilung, in welcher zweizentrige Bond-Orbitale die Bindungselektronen undsp ³-Hybride die einsamen Elektronenpaare beschreiben. Eine dreitermige Fourier-Approximation des erhaltenen Potentialverlaufs hat die Gestalt:U() = const. + 5,248 · cos + 2,592 · cos 2 + 0,142 · cos 3 [kcal · Mol^–1] .Für die PotentialschwellenU _cis undU _trans ergeben sich 11,76 bzw. 0,98 kcal · Mol^–1, dem Minimum der Potentialkurve entspricht ein Torsionswinkel von 120,5°.

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Using the Hellmann-Feynman-theorem the potential of internal rotation of H₂0₂ is calculated, the electronic charge distribution being represented by two-center bond orbitals andsp ³ hybrid orbitals (for the lone pairs). Developing the calculated potential in a Fourier series leads to the above-mentioned formula. The potential barries are 11.76 and 0.98 kcal/Mole, the angle of twist of equilibrium is 120.5°.

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Resume On calcule à l'aide du théorème de Hellmann Feynman le potentiel de rotation interne de H₂O₂. La distribution de charge électronique de la liaison OH nécessaire pour ce calcul est représentée par une fonction de liaison à 2 centres tirée d'un calcul d'orbitales de liaison de l'eau. Le développement en série de Fourier du potentiel donne:U() = 3.780 + 5.248 cos + 2.592 cos 2 + 0.142 cos 3 [kcal · Mol^–1] .Pour les barrières de potentiel on obtient les valeursU _cis = 11.76 et Urane = 0.98 kcal/Mole; l'angle d'équilibre est trouvé égal à 120° 5.

     

Synthesis and Crystal Structure of Diaqua(2.2.2-Cryptand)strontium Dichloride Trihydrate

Absract—Diaqua(2.2.2-Cryptand)strontium dichloride trihydrate [Sr(2.2.2-Crypt)(H₂O)₂]²⁺ · 2Cl^– · 3H₂O (I) was prepared and studied by X-ray diffraction. The triclinic structure of I (space group P , a = 9.152 Å, b = 10.140 Å, c = 15.219 Å, = 88.84°, = 88.19°, = 87.62°, Z = 2) was solved by the direct method and refined by full-matrix least-squares calculations in the anisotropic approximation to R = 0.050 for 4188 independent reflections (CAD4 automated diffractometer, CuK radiation). The structure contains the [Sr(2.2.2-Crypt)(H₂O)₂]²⁺ host–guest cation. The Sr²⁺ cation resides in the 2.2.2-cryptand cavity and is coordinated by all eight heteroatoms (6O + 2N) of the cryptand ligand and by two O atoms of water molecules. The Sr²⁺ coordination polyhedron (C.N. 10) is a highly distorted dibase-centered two-cap trigonal prism. The crystal structure of I contains a branched system of ion–ion (intermolecular) hydrogen bonds O(w)–H···Cl^–, which connect the complex cations, the Cl^– anions, and the crystal water molecules to form infinite thick layers parallel to the yz plane.     

Synthesis,spectroscopic and structural studies of tris(3-methyl-pyridinium)(3-ethylpyridinium)β-octamolybdate monohydrate

Summary Three isostructural compounds of general formula (3-MepyH) _x (3-EtpyH)_4–x [Mo₈O₂₆] (x=0, 2, 4) crystallize in the monoclinic system, space group P2₁/n, Z=2. Previously determined parameters for the compoundx=4 area=13.652(2),b=10.887(1),c=13.759(1) Å, =90.87(1)°,V=2044.8(4) ų,Dx=2.53,Do=2.54(1) mg m^–3,F(000)=1496. Slight differences in cell dimensions have been observed whenx=0 or 2. A nonisomorphous compound of formula (3-MepyH)₃(3-EtpyH)[Mo₈O₂₆]·H₂O crystallizes in the triclinic system, space group P2₁/n,Z=2,a=10.918(1),b=10.985(3),c=18.991(2) Å, =97.19(2), =91.45(2), =107.30(2)⁰,V=2152.8(7) ų,Dx=2.456,Do=2.456(5) mg m^–3,F(000)=1532. The distinguishing features of tris(3-methylpyridinium)(3-ethylpyridinium) -octamolybdate monohydrate are its non-centrosymmetric polyanion and its extensive hydrogen bonding. The asymmetric unit contains three independent 3-methylpyridinium and one 3-ethylpyridinium cations, one water molecule and the -octamolybdate anion. The planar cations are oriented to permit hydrogen bonds with either molybdate oxygen atoms or water oxygen atoms. Four different types of hydrogen bonds have been found: N–H...O (mono- and bifurcated); N–H...Ow (monofurcated); Ow–Hw...O (monofurcated); and C–H...O (monofurcated). The proposed hydrogen bonding interactions appear to stabilize the structure.     

Synthesis and Characterization of the Isocyanide Ligated Centered Zirconium Halide Cluster [(Zr6Be)Cl12(CNXyl)6]

The first isocyanide ligated hexanuclear zirconium halide cluster is reported. The unoxidized [(Zr₆Be)Cl₁₂(CNXyl)₆] (CNXyl = 2,6-dimethylphenyl isocyanide) was obtained from the solid state precursor K₃Zr₆Cl₁₅Be by dissolution in CH₃CN in the presence of CNXyl. The CNXyl ligands occupy all the axial positions on the cluster. The compound was recrystallized from CH₂Cl₂ and Et₂O. [(Zr₆Be)Cl₁₂(CNXyl)₆].2CH₂Cl₂ crystallizes in the space group (#2) with a = 12.092(5) Å, b=12.728(5) Å, c = 14.102(8) Å, = 104.98(4)°, =107.11°, = 100.94°, V = 1919(2) ų, Z = l, R = 11.3% and R _W = 27.0%. For the bound isocyanide ligands, v _CN increases to 2140 cm^–1.     

Kinetics and mechanism of the copper(II) promoted hydrolysis of the methyl ester of ethylenediaminemonoacetate

Summary Base hydrolysis of methyl ethylenediaminemonoacetate has been studied at I=0.1 mol dm^–3 (NaClO₄) over the pH range 7.4–8.8 at 25 °C. The proton equilibria of the ligand can be represented by the equations, where E is the free unprotonated ester species. Values of pK₁ and pK₂ are 4.69 andca. 7.5 at 25° (I=0.1 mol dm^–3). For base hydrolysis of EH⁺, k_OH=1.1×10³ dm³ mol^–1 s^–1 at 25 °C. The species E is shown to undergo lactamisation to give 2-oxopiperazine (k_lact ca. 1×10^–3 s^–1) at 25 °C. Formation of the lactam is indicated both by u.v. measurements and by isolation and characterisation of the compound.Base hydrolysis of the ester ligand in the complex [CuE]²⁺ has been studied over a range of pH and temperature, k _OH ²⁵ =9.3×10⁴ dm³ mol^–1 s^–1 with H=107 kJ mol^–1 and S ₂₉₈ =209 JK^–1 mol^–1. Base hydrolysis of [CuE]²⁺ is estimated to be some 10⁵5 fold faster than that of the free ester ligand. The results suggest that base hydrolysis occursvia a chelate ester species in which the methoxycarbonyl group of the ligand is bonded to copper(II).     

Pseudohalogen compounds of astatine: Synthesis and characterization of At/I/-tricyanomethanide-and At/I/-azide-compounds

Reactions of At//⁺, At^o.H₂O, AtCl ₂ ^– and AtBr₂ with the pseudohalogenides tricyanomethanide and azide are described. Information on the compound formation of astatine with C/CN/ ₃ ^– and N ₃ ^– could be obtained on the basis of electromigration investigations under variation of the conditions /composition of the electrolyte, pH, exchange reactions of ligands/. For the reaction: [At/H₂O/C/CN/₃]+C/CN/ ₃ ^– [At/C/CN/₃/₂]+H₂O at 301 K and u=0.075 mol.l^–1 K₂=/675±25/ [1.mol^–1] and u^o=–/3.50±0.10/×10^–4 [cm².s^–1.V^–1]. According to this astatine/I/-tricyanomethanide is classified between AtI ₂ ^– and At/SCN/ ₂ ^– . First investigations in azid-containing systems confirm the formation of astatine/I/-azide-compounds. Their composition is probably At/N₃/ ₂ ^– . There is no dependence of the ion mobility of astatine/I/-azide in the investigated range on azide concentration which is due to its high stability.     

Kinetics of base hydrolysis of trans-{Cr([15]aneN4)Cl2}+ ([15]aneN4 = 1,4,8,12-tetra-azacyclopentadecane)

Summary Reaction of CrCl₃(DMF)₃ with [15]aneN₄ (L; L = 1,4,8,12-tetra-azacyclopentadecane) gives the green trans-{Cr([15]-aneN ₄)Cl₂}Cl in high yield. The base hydrolysis kinetics of the cations [CrLCl₂]⁺ and [CrLCl(OH)] ⁺ have been investigated over a temperature range. For the dichloro complex, k _OH = 1.03 dm³ mol^–1 s^–1] at 25° C with H =30.4 kJmol^–1 and S _inf298 ^sup = -143 JK^–1 mol^–1. The substantial negative entropy of activation implies more association of water in the loss of Cl^– from the conjugate base in a D_CB mechanism. The kinetic parameters for the chlorohydroxo complex are k _OH = 1.9 × 10^–2dm³mol^–1 s^–1 at 25°C with H = 78.3kJmol^–1 and H _inf298 ^sup = -15 J K^–1 mol ^–1. The chlorohydroxo complex probably has the trans VI configuration with the chloride ligand on the same side of the equatorial plane as the four chiral sec-NH groups. The visible spectra of a variety of complexes trans-[Cr(L)XY] ⁿ⁺ (X = Y = Cl, OH, OH₂; X = Cl, Y = OH) have been determined.     

Multinuclear macromolecule metal complexes 2. Preparation and characterization of Prussian blue and its analogs bonded to pofy(vinylamine hydrochloride)

Prussian blue and its analogs bonded to poly(vinylamine hydrochloride) (PVAm · HCl) containing Fe^II or Fe^III and M²⁺ (M=Fe, Co, Cu) in a 11 molar ratio were obtained by the reaction of [Fe(CN)₆] ^n– (n=3,4) with M²⁺ ion-PVAm · HCl mixture in aqueous solution. Under a limited polymer concentration (T_VAm/T_Fe over 10), these polymer complexes thus obtained were stable and soluble in water. By casting these solutions, colored films can be produced. The formation of Prussian blue and its analogs bonded to PVAm · HCl was also investigated by the Benesi-Hildebrand method. The molar extinction coefficients of intervalence charge transfer (Fe^IIFe^III, Co^IIFe^III, Fe^IICu^II) band for MFe(CN)₆]^(n–2)– bound to PVAm · HCl (M=Fe, Co, Cu) were found to be 10,100–9601 · mol^–1 · cm^–1 at 25 C. The formation constants were found to be in the range of 10⁷ to 10¹⁰ M^–1. The changes of enthalpy (H) and entropy (S) were found to be in the range of –10.4 to –22.5 kJ · mol^–1 and 5.7 to 52.9 J · K^–1 mol^–1 respectively, at 25C.     

Kinetics and mechanism of pentacyanohydroxoferrate(III) formation from [FeL(OH)2]− complex, (L=N-(2-hydroxyethyl) iminodiacetate anion

Summary The kinetics and mechanism of the system [FeHIDA-(OH)₂]^–+5CN^–[Fe(CN)₅OH^–+HIDA^2–+OH^– (HIDA=N-(2-hydroxyethyl) (iminodiacetate) at pH=9.5±0.02, I=0.1 M and at 25±0.1°C have been studied spectrophotometrically at 395 nm ( _max of [Fe(CN)₅OH]^3–]. The reaction has three distinguishable stages; the first is formation of [Fe(CN)₅OH]^3–, the second is conversion of [Fe(CN)₅OH]^3– into [Fe(CN)₆]^3–, and last is the reduction of [Fe(CN)₆]^3– to [Fe(CN)₆]^4– by the HIDA^2– released in the first stage. The first stage shows variable-order dependence on cyanide concentration, unity at high cyanide concentration and zero at low cyanide concentration. The second stage exhibits first-order dependence on the concentration of [Fe(CN)₅OH]^3– as well as on cyanide. The reverse reaction between [Fe(CN)₅OH]^3– and HIDA^2– is first-order in each of these species and inverse first-order in cyanide. On the basis of forward and reverse rate studies, a five-step mechanism has been proposed for the first stage. The first step involves a slow loss of one OH^–, by a cyanide-independent path.     

Copper(II) halide reactions with the - NH · CS - group in heterocyclic pentaatomic rings

Summary White crystalline complexes of general formula Cu₂L₄X₂ (where X = Cl, Br and L = 1, 3-oxazolidine-2-thione, pyrrolidine-2-thione,N-methyl-1,3-imidazolidine-2-thione andN-ethyl-1,3-imidazolidine-2-thione) and CuLX (where L = 1,3-imidazolidine-2-thione) were prepared by reduction of copper(II) halides and studied by i.r. spectroscopy in the 4000–200 cm^– range. Evidence for ligand coordination to the metal through sulphur was found in each case. The(CuCI) vibration in all the chloro derivatives falls atca. 240 cm^–.     

Chromium(VI), chromium(V) and chromium(IV) oxidation of 12-tungstocobaltate(II)

The reaction between Cr^VI and 12-tungstocobaltate(II) was carried out in 2.0 mol dm^–3 HCl and followed a simple second order rate law. The reaction was catalysed by hydrogen ion due to the formation of active H₂CrO₄ and was inhibited by chloride ion as, in its presence, conversion of the active species into inactive chlorochromate occurs. Chromium(V) and chromium(IV) were generated in situ by the use of Cr^VI—V^IV or Cr^VI—2-ethyl-2-hydroxybutyric acid and Cr^VI—i-PrOH reactions respectively, and the oxidation of 12-tungstocobaltate(II) by these atypical oxidation states, was also studied. The rate constants for the oxidation of 12-tungstocobaltate(II) by Cr^VI, Cr^V and Cr^IV were found to be in the ratio 1:1.2:5.2 respectively. The ionic strength did not affect the reaction, while decrease in the solvent polarity increased the rate of the reaction. The activation parameters were also determined and the values H , G and S were found to be 52.4 ± 6 kJ mol^–1, 100.8 ± 7 kJ mol^–1, –151.7 ± 10 J K^–1 mol^–1 respectively, supporting the mechanism proposed.     

Syntheses,crystal structures,and characterizations of two novel cubane-like and double cubane-like molybdenum-copper-sulphur clusters {MoCu3S3(S2COEt)}(O)(Ph3P)3 and {Mo2Cu6S6(SCMe3)2}(O)2(Ph3P)4

Two novel heterometallic cubane-like and double cubane-like clusters, {MoCu₃S₃(S₂COEt)}(O)(Ph₃P)₃ I and {Mo₂Cu₆S₆(SCMe₃)₂}(O)₂(Ph₃P)₄ II, were synthesized by reaction of {MoCu₂S₃}(O)(Ph₃P)₃ with CuS₂COEt and CuSCMe₃, respectively. ClusterI crystallized in the triclinic space group (2) witha=12.766(6) Å,b=22.904(5) Å,c=10.522(3) Å, =99.86(2)°, =109.68(2)°, =86.84(3)°,V=2854(2) ų,Z=2,R=0.049 for 6622 observed reflections (I>5(I)) and 410 variables. ClusterII crystallized in the triclinic space group (2) with dimensionsa=14.212(4) Å,b=14.725(5) Å,c=12.396(8) Å, =110.32(4)°, =90.40(5)°, =62.88(2)°,V=2129(2) ų,Z=1,R=0.039 for 6020 observed reflections (I>3(I)) and 461 variables. ClusterI consists of a neutral cubane-like molecule with the core {MoCu₃S₃(S₂COEt)}²⁺, in which one corner of the cubane-like core is a novel triply bridging bidentate 1,1-dithiolato (xanthate, S₂COEt^–) ligand. ClusterII is a double cubane-like one, in which two cubane-like cores {MoCu₃S₃(SCMe₃)}²⁺ are connected by two Cu-S bonds of the triply bridging monothiolato (SCMe ₃ ^– ) ligand. Two different pathways of unit construction from a small heterometallic cluster {MoCu₂S₃}(O)(Ph₃P)₃ have been outlined. Comparisons of the selected bond lengths and bond angles for the cubane-like core {MoCu₃S₃ X} (X=Cl^–, Br^–, S₂COEt^–, SCMe ₃ ^– ) are given. Spectroscopic properties of the title clusters are also reported.     

The preparation and characterisation of chromium(III) complexes of C-meso-5, 12-dimethyl-1, 4, 8, 11-tetraazacyclotetradecane (LM). Aquation and base hydrolysis kinetics ofcis- andtrans-[CrLMCl2]+

Summary The reaction of [CrCl₃(DMF)₃] with C-meso-5, 12-dimethyl-1, 4, 8, 11-tetra-azacyclotetradecane(L_M) in DMF gives a mixture ofcis-[CrL_MCl₂]Cl (ca. 90%) andtrans-[CrL_MCl₂]Cl (ca. 10%). These complexes are readily separated, as thecis-isomer is insoluble in warm methanol while thetrans-isomer is soluble. Using the dichlorocomplexes as precursors it has been possible to prepare a range ofcis-[CrL_MX₂]⁺ complexes (X=Br^–, NO ₃ ^– , N ₃ ^– , NCS^– and X₂=bidentate oxalate) and alsotrans-[CrL_MX₂]⁺ complexes (X=Br^–, H₂O or NCS^–). The spectroscopic properties and detailed stereochemistry of the complexes are discussed.The aquation and base hydrolysis kinetics ofcis- andtrans-[CrL_MCl₂]⁺ have been studied at 25° C. Base hydrolysis of thecis-complex is extremely rapid with K_OH =1.46×10⁵ dm³ mol^–1 at 25° C. This unusual reactivity appears to be associated with thetrans II stereochemistry of thesec-NH centres of the macrocycle. Base hydrolysis of thetrans complex with thetrans III chiral nitrogen stereochemistry is quite normal with k_OH =1.1 dm³ mol^–1 s^–1 at 25° C.     

Thermodynamics of Protonated Amine–Hexacyanoferrate(II) Complex Formation in Aqueous Solution

Thermodynamic parameters, G°, H° and TS° are reported for the formation of proton amine–hexacyanoferrate(II) complexes, in aqueous solution, at 25°C. H° were determined by the temperature dependence of formation constants and/ or by direct calorimetry in aqueous solution, at T = 25°C. Enthalpy changes for the reaction H_iAⁱ⁺ + H_j Fe(CN) ₆ ^j-4 = AFe (CN)₆H _i+j ^i+j-4 (where A = methylamine, ethylenediamine, and tetraethylenepentamine) are quite low and the main contribution to the stability of these complexes arises from the entropic term, as expected for electrostatic interactions. When j = 0, the formation entropy is linearly dependent on i according to the simple equation TS° = 13.4 i kJ-mol^–1.     

Estimation of the porous structure of active carbons

Active carbons from apricot, plum, peach, and grape stones were prepared. The analysis of adsorption isotherms of benzene vapor showed that the active carbons obtained from fruit stones have highly homogeneous microporous structures withW ₀ 0.30 cm³ g^–1,E ₀ 24.5 kJ mol^–1, andx ₀ 0.42 nm, and they contain ultramicropores along with micropores.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1934–1936, October, 1995.This study was financially supported by the Russian Foundation for Basic Research (Project No. 94-03-09550).