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].     

f-Element/crown ether complexes: 21. Conformational changes in metal complexed versus hydrogen bonded benzo-15-crown-5 in the structure of [Y(OH2)3(NCMe)-(benzo-15-crown-5)][ClO4]3·benzo-15-crown-5·CH3CN

Crystalline [Y(OH₂)₃(NCMe)(benzo-15-crown-5)][ClO₄]₃·benzo-15-crown-5-CH₃CN can be obtained by slowly cooling a reaction mixture of Y(ClO₄)₃·n H₂O with benzo-15-crown-5 in a solution of acetonitrile and methanol (3 : 1) from 60°C to room temperature. The crystal structure of this complex has been determined at –150 and 20°C. The complex is triclinic,P . At –150°C the cell parameters area = 11.986(4),b = 12.071(7),c = 16.364(5) Å, = 93.56(3), = 98.68(3), = 109.68(4)°, vol = 2187 ų, andD _calc = 1.61 g cm^–3 forZ = 2 formula units. 3633 independently observed [F _o 5(F _o)] reflections were used in the final least-squares refinement leading to an agreement index ofR = 0.048. The Y(III) ion coordination geometry approximates a tricapped trigonal prism with three water molecules and three benzo-15-crown-5 oxygen atoms forming the prism, with the two remaining benzo-15-crown-5 oxygen atoms and the acetonitrile molecule completing the coordination as capping atoms. The three water molecules hydrogen bond a second crown ether molecule and two of the perchlorate anions. The two acetonitrile molecules have contacts with perchlorate oxygen atoms close enough for some weak interaction. One perchlorate is ordered, one is partially disordered as is the coordinated solvent molecule, and the third anion is totally disordered. The two unique crown ether molecules have distinctively different conformations.For Part 20, see reference [1].     

Crystal Structure of 1,10-Diazonia-18-crown-6 Bis(hydrogen oxalate) and 1,10-Diazonia-18-crown-6 Oxalate Dihydrate

An X-ray diffraction study has been performed to study the crystal structure of 1,10-diazonia-18-crown-6 bis(hydrogen oxalate) [H₂DA18C6]²⁺·2C₂HO ₄ ^- (I) and 1,10-diazonia-18-crown-6 oxalate dihydrate [H₂DA18C6]²⁺·2C₂O ₄ ^- ·2H₂O (II). Crystals I are triclinic: space group , a = 7.825, b = 7.861, c = 9.349 , = 97.28, = 110.22, = 99.12°, Z = 1. Crystals II are monoclinic: space group P2 ₁ /n, a = 8.783, b = 10.640, c = 10.225 , = 97.04°, Z = 2. The structures of I and II were solved by direct methods and refined by the full-matrix least-squares procedure anisotropically to R = 0.036 (I) and 0.042 (II) for all 2206 (I) and 1990 (II) unique reflections measured (CAD-4 automatic diffractometer, CuK ). In the crystal structures, the ionic complexes (salts) I and II are not individual guest–host complex molecules but are parts of complex (infinite in two directions) three-dimensional layers of H-bonded molecular anions and DA18C6 dications (and water molecules in II). In structures I and II, the centrosymmetric DA18C6 dications have different conformations: two-angle in I and four-angle in II. The unusual four-angle conformation of the DA18C6 dication was found for the first time.     

On the reliability of equilibrium data of the charge-transfer complex between 2,3-dichloro-1,4-naphthoquinone and hexamethylbenzene

In view ofHammond's warning⁶ about the Conspiracy of errors, found in the case of low values of equilibrium constants of charge-transfer complexes a case is made out for redetermining the values for the system hexamethylbenzene—2,3-dichloro-1,4-naphthoquinone. Uncertainties in the parameters were estimated using theLiptay ⁸ matrix procedure. The solvent used was dichloromethane. The following data were obtained at 25°C: vC T = 22,220 cm^–1;E _A=0.99 eV;K =2599±57 l²·cm^–1·mol^–2. _max= 1020 ± 148 cm^–1··1;K=2.55±0.37 l·mol^–1; –H=2.7±0.3 kcal·mol^–1.With 1 Figure     

Behavior of M[Al2Me6N3] (M=K,Rb, Cs) with aromatic solvents and the crystal structures of Cs[Al2Me6N3]·2p-xylene and [K·dibenzo-18-crown-6] [Al2Me6N3]· 1.5(1-methylnaphthalene)

The title compounds were synthesized by the addition of AlMe₃ to the corresponding azide suspended in an aromatic solvent. Both products were obtained as air-sensitive colorless crystals. Cs[Al₂Me₆N₃]·2p-xylene crystallizes in the monoclinic space groupC2/m witha=19.143(6),b=16.227(6),c=10.392(5) Å, =114.06(2)^o, and _calc = 1.20 g cm^–3 forZ=4. Refinement led to a conventionalR value of 0.037 for 2179 observed reflections. The cesium atom resides on a mirror plane, and the anion is disordered about a twofold axis. Thep-xylene molecules sandwich the cesium ion.[K·dibenzo-18-crown-6] [Al_Me6N₃]·1.5(1-methylnaphthalene) crystallizes in the monoclinic space groupP2₁/c witha=14.176(5),b=13.021(5),c=25.324(8) Å, =98.23(4)⁰, and _calc = 1.08 g cm^–3 forZ=4. The finalR value was 0.132 for 1402 observed reflections. One of the 1-methylnaphthalene molecules is disordered about a center of inversion and interacts with the potassium ion. The other solvent molecule is found roughly in layers in the lattice and also exhibits disorder of the methyl substituent. For both title compounds the AlMe₃ groups of the anion exhibit a staggered (C _s) conformation. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82015 (32 pages).     

4,4′-Dipyridyl and 2,2′-dipyridyl complexes of rare-earth perchlorates

4,4-Dipyridyl and 2,2-dipyridyl complexes of rare-earth perchlorates of the formulaLn(4-dipy)₈(ClO₄)₃HClO₄ · 4H₂O (Ln=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, Lu, Y, 4-dipy=4,4-dipyridyl) andLn(2-dipy)₃(ClO₄)₃ · 6H₂O (Ln=Pr, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, Lu, Y, 2-dipy = 2,2-dipyridyl) have been synthesized. The IR spectra of these compounds and other physical properties are discussed.

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4,4-Dipyridyl- und 2,2-Dipyridylkomplexe von Seltenerdmetallperchloraten

Zusammenfassung Es wurden 4,4-Dipyridylkomplexe des TypsLn(4-dipy)₈(ClO₄)₃HClO₄ · · 4 H₂O mitLn=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, Lu, Y und 2,2-Dipyridylkomplexe des TypsLn(2-dipy)₃(ClO₄)₃ · 6 H₂O mitLn=Pr, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, Lu und Y dargestellt. Die IR-Spektren und andere physikalische Eigenschaften werden diskutiert.

     

The Influence of 4f Orbital Excitation in Eu(Fod)3 on Complexation with Sulfones in Benzene Solutions

Complexation of sulfones (S) with the -diketonate Eu(Fod)₃ (Fod–heptafluorodimethyloctanedione) in the ground and excited electronic states in benzene solutions was studied. The stability constants and thermodynamic parameters for the formation of complexes Eu(Fod)₃ · S in the ground state (K, H ₀, S ₀) and Eu(Fod)₃ ^* · S in the excited state (K*, H ₀ ^*, S ₀ ^*) were determined. The excitation of f–f transitions of Eu(III) was found to enhance the stability of Eu(Fod)₃ · S complexes, apparently due to an increase in the acceptor ability of the Eu(III) chelate. This fact confirms the involvement of the 4f orbital in the chemical bond formation. The compensation effect was observed for the thermodynamic parameters: S ₀ = (2.9 ± 0.3) × 10^–3H ₀ + (35.0 ± 4.0) in the ground and S ₀ ^* = (3.3 ± 0.3) × 10^–3H ₀ ^* + (49.0 ± 5.0) in the excited states of Eu(Fod)₃. It was shown that electronic excitation of the 4f orbital of Eu(Fod)₃ influences isotopic effects in complexation with sulfolanes.     

Phase equilibria in the Ag4SSe-SnTe system

The phase diagram of the system Ag₄SSe-SnTe is studied by means of X-ray diffraction, differential thermal and metallographic analyses and measurements of the microhardness and the density of the material. This diagram is divided into two eutectic-type subdiagrams by the composition Ag₄SSe·2SnTe. The unit-cell parameters of the intermediate phases 3Ag₄SSe·SnTe (phase A) and -Ag₄SSe·2SnTe (phase B) are determined as follows: for phase A: a=0.7851 nm, b=0.7196 nm, c=0.6296 nm, =101.32°, =85.90°, =111.36°; for phase B: a=0.3662 nm, b=0.3303 nm, c=0.3343 nm, =90.74°, =108.94°, =91.91°. The phase Ag4SSe·2SnTe melts congruently at 615°C and a polymorphic transition of the phase takes place at T _- =110°C.This revised version was published online in November 2005 with corrections to the Cover Date.     

f-Element/crown ether complexes, 11. Preparation and structural characterization of [UO2(OH2)5] [ClO4]2·3(15-crown-5)·CH3CN and [UO2(OH2)5] [ClO4]2·2(18-crown-6)·2 CH3CN·H2O

The reaction of UO₂(ClO₄)·nH₂O with 15-crown-5 and 18-crown-6 in acetonitrile yielded the title complexes. [UO₂(OH₂)₅] [ClO₄]₂·3(15-crown-5)·CH₃CN crystallizes in the triclinic space groupPT with (at–150°C)a=8.288(6),b=12.874(7),c=24.678(7) Å, =82.62(4), =76.06(5), =81.06(5)°, andD _calc=1.67 g cm^–3 forZ=2 formula units. Least-squares refinement using 6248 independent observed reflections [F _o5(F _o)] led toR=0.111. [UO₂(OH₂)₅] [ClO₄]₂·2(18-crown-6)·2CH₃CN·H₂O is orthorhombicP2₁2₁2₁ with (at–150 °C)a=12.280(2),b=17.311(7),c=22.056(3) Å,D _calc=1.68 g cm^–3,Z=4, andR=0.032 (3777 observed reflections). In each complex the crown ether molecules are hydrogen bonded to the water molecules of the pentagonal bipyramidal [UO₂(OH₂)₅]²⁺ ions, each crown ether having exclusive use of two hydrogen atoms from one water molecule and one hydrogen from another water molecule. In the 15-crown-5 complex the remaining hydrogen bonding interaction is between one of the water molecules and one of the perchlorate anions. The solvent molecule has a close contact between the methyl group and a perchlorate anion suggesting a weak interaction. There are a total of three U-OH...OClO₃ hydrogen bonds to the two perchlorate anions in [UO₂(OH₂)₅] [ClO₄]₂·(18-crown-6)·2CH₃CN ·H₂O. The remaining coordinated water hydrogen bond is to the uncoordinated 2H₂O molecule, which in turn is hydrogen bonded to a perchlorate oxygen atom and an acetonitrile nitrogen atom. One solvent methyl group interacts with an anion, the other with one of the 18-crown-6 molecules. Unlike the 15-crown-5 structure, the hydrogen bonding in this complex results in a polymeric network with formula units joined by hydrogen bonds from one of the solvent molecules and the uncoordinated water molecule. Supplementary data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82051 (37 pages).For Part 10, see reference [1].     

Palladium Clusters Pd4(SEt)4(OAc)4and Pd6(SEt)12: Structure and Properties

Palladium clusters Pd₄(SEt)₄(OAc)₄(I) and Pd₆(SEt)₁₂(II) were synthesized and studied. Their structure was determined by X-ray diffraction analysis. For I, a= 9.774(2) Å, b= 10.821(2) Å, c= 13.061(3) Å, = 92.88(3)°, V= 1379.6(5) ų, (calcd.) = 2.182 g/cm³, space group P2₁/n, Z= 4, N _ref= 1558, and R= 0.031; for II, a= 10.581(1) Å, b= 10.584(2) Å, c= 11.478(2) Å, = 101.62(1)°, = 104.95(1)°, = 106.74(1)°, V= 1135.2(4) ų, (calcd) = 2.007 g/cm³, space group P1, Z= 1, N _ref= 2828, and R= 0.022. In cluster I, four Pd atoms form a planar cycle. The neighboring palladium atoms are bound by two acetate or by two mercaptide bridges, the Pd···Pd distances being 3.036–3.195 Å. In cluster II, Pd atoms form a planar six-membered cycle with Pd···Pd distances of 3.083–3.127 Å. The neighboring palladium atoms are bound by two mercaptide bridges. The formation of analogous clusters in solution was confirmed by IR spectroscopy.     

Crystal Structure of Ammonium Undecafluorotriantimonate(III) (NH4)2Sb3F11

The crystal structure of a novel antimony(III) fluoride complex, ammonium undecafluorotriantimonate(III) (NH₄)₂Sb₃F₁₁, was determined. The crystals are triclinic: a = 7.780(2) Å, b = 8.370(2) Å, c = 10.620(1) Å, = 71.06(1)°, = 89.03(1)°, = 63.58(1)°, V = 579.1(2) ų, Z = 2, (calcd) = 3.500 g/cm³, (exp) = 3.51 g/cm³, F(000) = 548.0, space group P . The structure consists of anionic [Sb₃F₁₁]^2– chains and ammonium cations combined into a framework by the N–H···F hydrogen bonds.     

A 2pπ, 3dπ valence bond wave function for the 1B1u state of ethylene

A 2p, 3d valence bond wave function for the lowest ¹ B _1u state of the -system of ethylene is variationally optimized with respect to the atomic orbital exponents using a non-empirical -approximation. The resulting energy compares favourably with previous calculations and leads to a satisfactory value for the lowest ¹ A _1g-¹ B _1u transition energy. The optimized exponent for the 2p orbital is close to the Slater value whereas the exponent for the 3d orbital is found to be nearly hydrogenic. The implications of this result are discussed in some detail.

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Zusammenfassung Für den tiefsten ¹ B _1u -Zustand des -Elektronensystems des Äthylens wird nach der Variations-methode eine 2p, 3d-Valenzbindungs-Wellenfunktion bezüglich der Orbitalkoeffizienten optimiert, wobei eine nicht-empirische -Approximation zugrunde gelegt wird. Die berechnete Energie stimmt gut mit den Ergebnissen vorausgegangener Rechnungen überein. Für den tiefsten ¹ A _1g ¹ B _1u -Übergang ergibt sich ein befriedigender Energiewert. Der optimierte Orbitalkoeffizient für das 2p-Orbital stimmt gut mit dem nach der Slaterschen Regel bestimmten Koeffizient überein, während man für den 3d-Orbitalkoeffizienten einen Wert findet, der dem des Wasserstoffs ähnlich ist.

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Résumé Une founction d'onde V.B.(2p , 3d ) est optimée pour l'état ¹ B _1u d'aethylen. L'energie calculé aussi que l'energie de transition la plus basse ¹ A _1g -¹ B _1u est en bon accord avec des valeurs connues.

     

Kinetic studies on the thermal dissociation of the inclusion complex of β-cyclodextrin with cinnamic aldehyde

The stability of the inclusion complex of -CD with cinnamic aldehyde was investigated by means of TG and DSC. The mass loss takes place in three stages: dehydration occurs at 50–120°C; dissociation of -CD·C₉H₈O proceeds in the range 200–260°C; and decomposition of -CD begins at 280°C. The kinetics of the dissociation of -CD·C₉H₈O was studied by means of thermogravimetry both at constant temperature and with linearly increasing temperature. The results demonstrate that the dissociation of -CD·C₉H₈O is dominated by a one-dimensional diffusion process. The activation energyE is 160 kJ mol^–1, and the pre-exponential factorA is 5.8×10¹⁴ min^–1. Scanning electron microscope observations and the results of crystal structure analysis are in good agreement with those of thermogravimetry.     

The designed synthesis and crystallographic characterization of three novel heterotrimetallic linear complexes of [Et4N][(Ph3P)2{M′S2 MS2Fe}Cl2] (M=Mo,M′=Ag;M=W,M′=Cu,Ag)

The complexes [Et₄N][(Ph₃P)₂{MS₂ MS₂Fe}Cl₂] (M=Mo,M=Ag;M=W,M=Cu, Ag) have been obtained by reaction of [Et₄N]₂[S₂ MS₂FeCl₂] (M=Mo, W) with Cu(PPh₃)₃Cl or Ag(PPh₃)₃NO₃ in MeCN/CH₂Cl₂, respectively. Crystal data for [Et₄N][(PPh₃)₂ {AgS₂MoS₂Fe}Cl₂] (I): triclinic, P (No. 2),Z=2,a=13.41(1)Å,b=15.54(1)Å,c=12.30(1)Å, =105.24(6)°, =94.63(7)°, =101.38(6)°, andV=2399(4)ų. The bond lengths of Mo-Fe bond and the Mo-Ag distance are 2.756(2)Å and 3.033(2)Å, respectively. Crystal data for [Et₄N][(PPh₃)₂ {AgS₂WS₂Fe}Cl₂] (II): triclinic, P (No. 2),Z=2,a=13.457(5))Å,b=15.601(6)Å,c=12.338(4)Å, =105.20(3)°, =94.61(4)°, =101.43(4)°, andV=2426(2)ų. The bond length of W-Fe bond and the W-Ag distance are 2.786(2)Å and 3.076(1)Å, respectively. Crystal data for [Et₄N][(PPh₃)₂ {CuS₂WS₂Fe}Cl₂] (III): triclinic, P (No. 2),Z=2,a=13.498(5)Å,b=15.372(4)Å,c=12.340(4)Å, =105.54(2)°, =93.32(3)°, =101.40(3)°, andV=2401(1)ų. The bond lengths of W-Fe bond and the W-Cu bond are 2.800(1)Å and 2.851(1)Å, respectively.     

Synthesis,characterization and x-ray structure of V3(μ3-O)(μ-Cl)Cl6(μ-η1-η1-PhNHNH2)2(PhNHNH2)2(THF) · 6THF: A new binding mode for phenylhydrazine

Addition of phenylhydrazine to a mixture of VCl₃ · THF/N,N-propyl-bis (salicyladimine) and sodium hydride yielded a trinuclear vanadium complex, V₃(₃-O)(-Cl)Cl₆(-¹-¹PhNHNH₂)₂(PhNHN H₂)₂(THF), containing two bridging and two terminal phenylhydrazine ligands. The product has been crystallographically characterized (P2₁/n, a=12.949(2) Å,b=24.061(4) Å,c=22.504(4) Å, =107.22(1) deg.,V=6697(2) ų withZ=4) and was found to contain the first example of bridging monosubstituted hydrazine (phenylhydrazine) ligands.     

Formation,properties, and thermal decomposition of bisarene chromium(i) and molybdenum(i) fullerides

Fullerides [(⁶-Ph₂)₂Cr]⁺[C₆₀]^·–, [(⁶-C₁₀H₁₂)₂Cr]⁺[C₆₀]^·– (C₁₀H₁₂ is tetralin), and [(⁶-PhCH₃)₂Mo]⁺[C₆₀]^·– were synthesized. The molecular structure of [(⁶-Ph₂)₂Cr]⁺[C₆₀]^·– was established. In this compound at 100 K, radical anions C₆₀ ^–· are linked by an ordinary bond to form dimers, whereas at 293 K they are disordered and do not form dimers. The [(⁶-tetralin)₂Cr]⁺[C₆₀]^·– fulleride is stable in vacuo (10^–2 Torr) below 429 K, and [(⁶-toluene)₂Mo]⁺[C₆₀]^·– is stable below 581 K.Based on the materials presented at the International Conference Modern Trends in Organoelement and Polymer Chemistry (Moscow, May 30–June 4, 2004) dedicated to the 50th anniversary of the A. N. Nesmeyanov Institute of Organoelement Compounds of the Russian Academy of Sciences.Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1973–1976, September, 2004.     

Hydrothermal Syntheses and Structural Characterization of Two Novel Arsenic–Vanadium Clusters: [Co(2,2′-bpy)3]2[As8V14O42(H2O)]·3H2O and [2,2′-bpy][Ni(2,2′-bpy)3]2[As8V14O42(H2O)]·3H2O

Two new arsenic–vanadium clusters, [Co(2,2- bpy)₃]₂[As₈V₁₄O₄₂(H₂O)] · 3H₂O (1), [2,2-bpy][Ni(2,2-bpy)₃]₂[As₈V₁₄O₄₂(H₂O)] · 3H₂O (2) (2,2-bpy=2,2-bipyridine), have been hydrothermally synthesized and characterized by IR, elemental analysis, UV–VIS, EPR, TGA, XPS, and single crystal X-ray diffraction analysis. Crystal data: 1, triclinic, P1, a=14.368(3) Å, b=16.753(3) Å, c=24.632(5) Å, =94.15(3)°, =93.16(3)°, =113.05(3)°, Z=2; 2, monoclinic, P2₁/c, a= 30.2150(4) Å, b=14.0690(3) Å, c=26.0536(3) Å, =106.8960(10)°, Z=4. X-ray crystallographic studies showed that crystals 1 and 2 are both composed of discrete cluster anion [As₈V₁₄O₄₂(H₂O)]^4– and transition metal coordination complexes [M(2,2-bpy)₃]²⁺ (M=Co or Ni). Interestingly, compound 2 contains another neutral organic space filler of 2,2-bpy. To the best of our knowledge, compounds 1 and 2 are the first examples of structurally characterized vanadium/2,2-bpy/arsenate polyoxometallates.     

Molecular structures of benzoylbenzo-12-crown-4 and diphenylacetylbenzo-12-crown-4 and possible reasons for different conformational states of their macrocycles

The molecular structures of (benzoyl)benzo-12-crown-4 (a=22.387,b=4.503,c=16.167 Å,d _calc=1.34 g cm^–3,Z=4, space groupP2₁ nc, DAR-UM, Cu-K,R=0.056) and (diphenylacetyl)benzo-12-crown-4 (a=8.866,b=23.337,c=10.737 Å;d _calc=1.25 g cm^–3,Z=4, space groupP2₁2₁2₁, DAR-UM, Cu-K, R=0.056) have been investigated. The differences in the conformations of the macrocycles and the degree of conjugation between the benzene ring orbitals and the lone pairs on the adjacent oxygen atoms in the macrocycle are discussed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1906–1911, November, 1993.     

A new route to the asymmetric Schiff base ligands. The ligand exchange in [Mo(CN)<Subscript>3</Subscript>O(salhy)]<Superscript>2−</Superscript> ion. Kinetics and mechanism

The kinetics of the ligand exchange in (PPh₄)₂[Mo(CN)₃O(salhy)]. 6H₂O (Hsalhy = salicylaldehyde hydrazone) by a solvent molecule and by 2,2-bipyridine (bpy) have been studied in EtOH. For the ligand exchange by a solvent molecule the pseudo-first order rate constant equals k _obs = 3.2 (±0.2) × 10^–3 s^–1 (t=25 °C), H =67 (± 7) kJ mol^–1, S =–75 (±23) J mol^–1 K^–1, while for the exchange by a bpy molecule k _obs=3.5 (±0.2) × 10^–3 s^–1 (t=25 °C), H =56 (±7) KJ mol^–1, S = –104 (±8) J mol^–1 K^–1. It was found, that all reactions proceed via the same mechanism which involves the chelate ring opening cis to the Mo=O bond. The mechanism of the reaction was proposed and was proved by the synthesis of (PPh₄)₂[Mo(CN)₃O(N-pic)]. 2.5H₂O (N-pic denotes that the nitrogen of picolinic acid is trans to Mo=O) by ligand exchange in EtOH, while in aqueous solution the O-pic analogue is formed exclusively.     

Superacid Univalent Metal Phosphites (MH2PO3)2· H3PO3 (M = Rb,Tl(I)) and MH2PO3· H3PO3(M = K,Cs): Synthesis and Structure

By reacting the K, Rb, Cs, or Tl carbonates with excess phosphoric acid, crystals of superacid phosphites, namely, (RbH₂PO₃)₂· H₃PO₃(I), (TlH₂PO₃)₂· H₃PO₃(II), KH₂PO₃· H₃PO₃(III), -CsH₂PO₃· H₃PO₃(IV), and -CsH₂PO₃· H₃PO₃(V), were synthesized. Their structures were determined by single-crystal X-ray diffraction analysis at 150 K. Crystals I: triclinic system, space group , a= 7.713(2) Å, b= 8.679(3) Å, c= 9.235(3) Å, = 79.36(3)°, = 67.60(2)°, = 88.13(3)°, R ₁= 0.0252; crystals II: triclinic system, space group , a= 7.690(3) Å, b= 8.494(3) Å, c= 9.292(4) Å, = 79.48(3)°, = 66.72(3)°, = 85.45(3)°, R ₁= 0.0485; crystals III: monoclinic system, space group P2₁/c, a= 8.726(3) Å, b= 12.182(4) Å, c= 6.354(2) Å, = 104.14(3)°, R ₁= 0.0241; crystals IV: orthorhombic system, space group P2₁2₁2₁, a= 6.033(1) Å, b= 6.444(1) Å, c= 18.345(4) Å, R ₁= 0.0172; crystals Vare monoclinic, space group C2/c, a= 9.990(3) Å, b= 12.197(4) Å, c= 6.866(2) Å. = 118.14(3)°, R ₁= 0.0181. The hydrogen bonding systems form corrugated bands (Iand II), bent layers (III), individual tubes with rectangular cross sections (V), or a three-dimensional framework (IV). A comparative analysis of the crystal structures of acid phosphites with different compositions was performed.