F/Cl-exchange on AlCl(3)-pyridine adducts: synthesis and characterization of trans-difluoro-tetrakis-pyridine-aluminum-chloride, [AlF2(Py)4]+Cl-

Whereas liquid CCl3F reacts with solid AlCl3 exothermically under chlorine-fluorine-exchange already above -20 degrees C, no reaction takes place between CCl3F and the pyridine complexes of AlCl3 (AlCl3.Py, AlCl3.2Py, or AlCl3.3Py) up to 100 degrees C. The desired chlorine by fluorine substitution on the monomer AlCl3-pyridine adducts occurs, however, easily using Me3SiF as fluorinating agent. By reacting AlCl3.3Py with Me3SiF (even up to 10-fold stoichiometric excess) in pyridine as a solvent, only two of the three Cl atoms can be substituted by fluorine, leading in good yield to the new "mixed aluminum halide", AlF2Cl.4Py. Actually, it represents the first example of a stable solid donor-acceptor adduct of an aluminum-III halide with two different halogens of defined stoichiometry. It was characterized by multinuclear solid-state NMR (27Al and 19F), IR spectroscopy, as well as single-crystal structure analysis. The new compound has an ionic solid-state structure with helical trans-octahedral [(Py)4AlF2]+ cations and isolated Cl- anions. The comparison of its 27Al MAS solid-state NMR spectra with those of a compound bearing the analogous [(Py)4AlCl2]+ cation reveals an extreme increase in the quadrupolar coupling constants, from 0.24 MHz in case of the chlorine cation to about 16 MHz in case of the new [(Py)4AlF2]+ cation.     

Aluminum chloride as a solid is not a strong Lewis acid

Aluminum chloride is used extensively as Lewis acid catalyst in a variety of industrial processes, including Friedel-Crafts and Cl/F exchange reactions. There is a common misconception that pure AlCl3 is itself a Lewis acid. In the current study, we use experimental and computational methods to investigate the surface structure and catalytic properties of solid AlCl3. The catalytic activity of AlCl3 for two halide isomerization reactions is studied and compared with different AlF3 phases. It is shown that pure solid AlCl3 does not catalyze these reactions. The (001) surface of crystalline AlCl(3) is the natural cleavage plane and its structure is predicted via first principles calculations. The chlorine ions in the outermost layer of the material mask the Al3+ ions from the external gas phase. Hence, the experimentally found catalytic properties of pure solid AlCl3 are supported by the predicted surface structure of AlCl3.     

Catalytic reactions of chlorofluoroethanes at fluorinated alumina and chromia aerogels and xerogels: A comparison of reaction pathways in alumina- and chromia-based catalysts

The differences in the dynamic behaviour of 1,1,2-trichlorotrifluoroethane over fluorinated alumina or chromia catalysts at moderate temperatures are significant. Alumina-based catalysts favour the isomerization of CCl₂FCClF₂ followed by the dismutation of CCl₃CF₃ so formed. Fluorinated chromias are less selective since halogen exchange and isomerization reactions both occur. An explanation in terms of the differences in Al---X, X=Cl or F, bond energies compared with their Cr---X counterparts is suggested. The identity of the catalyst precursor has little effect in the chromium case and no effect in the case of aluminium.     

Synthese und Struktur neuer Natriumhydrogensulfate Na(H3O)(HSO4)2; Na2(HSO4)2(H2SO4) und Na(HSO4)(H2SO4)2

Synthesis and Structure of New Sodium Hydrogen Sulfates Na(H₃O)(HSO₄)₂, Na₂(HSO₄)₂(H₂SO₄), and Na(HSO₄)(H₂SO₄)₂ Three acidic sodium sulfates have been synthesized from the system sodium sulfate/sulfuric acid and have been crystallographically characterized. Na(H₃O)(HSO₄)₂ ( A ) crystallizes in the space group P2₁/c with the unit cell parameters a = 6.974(2), b = 13.086(2), c = 8.080(3) Å, α = 105.90(4)°, V = 709.1 Å3, Z = 4. Na₂(HSO₄)₂(H₂SO₄) ( B ) is orthorhombic (space group Pna2₁) with the unit cell parameters a = 9.970(2), b = 6.951(1), c = 13.949(3) Å, V = 966.7 ų and Z = 4. Na(HSO₄)(H₂SO₄)₂ ( C ) crystallizes in the triclinic space group P1 with the unit cell parameters a = 5.084(1), b = 8.746(1), c = 11.765(3) Å, α = 68.86(2)°, β = 88.44(2)°, γ = 88.97(2)°, V = 487.8 Å3 and Z = 2. All three compounds contain SO₄ tetrahedra as HSO₄^? anions and additionally in B and C in form of H₂SO₄ molecules. The ratio H:SO₄ determines the connectivity degree in the hydrogen bond system. In A , there are zigzag chains and dimers additionally connected via oxonium ions. Complex chains consisting of cyclic trimers (two HSO₄^? and one H₂SO₄) are present in B . In structure C , several parallel chains are connected to columns due to the greater content of H₂SO₄. Sodium cations show a distorted octahedral coordination by oxygen in all three structures, the NaO₆ octahedra being “isolated” (connected via SO₄ tetrahedra only) in A . Pairs of octahedra with common edge form Na₂O₁₀ dimeric units in C . Such double octahedra are connected via common corners forming zigzag chains in B .     

The thermal behavior of triethylenediammonium salts

(trienH₂)[CoCl₄], which contains tetrahedral chlorocobaltate(II) anions, decomposes under argon in two stages via a stepwise deprotonation of the cation. The decomposition starts at 310°C with the liberation of HCl, followed at 400°C by the simultaneous release of a further mole of HCl and triene and/or its cracking products. The second decomposition stage is strongly influenced by the atmosphere. In the lower temperature region (<400°C), increasing oxygen contents of the carrier gas lead to decreasing mass losses. Therefore, the solid residues contain various amounts of C,N-containing products as well as coke. The thermal decomposition of the iron(III) compound, which contains μ-oxalato-bridged FeCl₄ units, begins with the dehydratation followed by the decay of the complex anion to produce CO, CO₂, and HCl. Instead of a binuclear, monooxobridged chloroferrate(III) complex, a [FeCl₄]^? — containing compound is proposed as one of the final products. The third decomposition stage, partially overlaying the preceding one, is the degradation of the organic cation as found for the cobalt compound. The results of thein situ-TA-MS measurements are compared with those obtained from usual TA techniques as well as from the residue characterization by X-ray diffraction, Raman spectroscopy, and chemical analysis.     

Zur Darstellung und Charakterisierung von Calciumhydrogensulfaten

Preparation and Characterization of Calcium Hydrogen Sulfate CaSO₄ · H₂SO₄ was identified as calcium hydrogen sulfate whereas CaSO₄ · 3 H₂SO₄ is an adduct of CaSO₄ with H₂SO₄. Depending on the excessive amount of H₂SO₄ both compounds exist side by side up to a temperature of 343 K, whereas above this temperature only Ca(HSO₄)₂ is stable. The DTA curve of Ca(HSO₄)₂ shows two maxima at 488 K and 523 K, according to the separation of H₂O under formation of pyrosulfate and decomposition of this compound under elimination of SO₃. In comparison with other hydrogen sulfates Ca(HSO₄)₂ shows a considerable increased O? H distances. The d-values of Ca(HSO₄)₂ are calculated and represented.     

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.     

Synthesis and crystal structures of bimetallic hydrogen sulfates M I M II [H(SO4)2](H2O)2 (M I = K, Cs; M II = Zn, Mn) and selenate KMg[H(SeO4)2](H2O)2

Single crystals of acid salt hydrates M ^I{M ^II[H(XO₄)₂](H₂O)₂}, where M ^I, M ^II, and X are K, Zn, and S (I); K, Mn, and S (II); Cs, Mn, and S (III); or K, Mn, and Se (IV), respectively, were synthesized and studied by X-ray diffraction analysis. Compounds I–IV (space group $P\bar 1$ ) are isostructural to each other and to hydrate KMg[H(SO₄)₂](H₂O)₂ (V) studied earlier. Structures I–V, especially, the M ^I-O, M ^II-O, and X-O distances and the O?H?O (2.44–2.48 Å) and O_w-H?O (2.70–2.81 Å) hydrogen bonds, are discussed.     

Neue Zirconiumphosphatfluoride mit 3D‐Gerüststruktur

New Zirconium Phosphate Fluorides with 3D‐Framework From aqueous solutions of ZrOCl₂, H₃PO₄, HF, and various amines, two new compounds of the general formula [amH₂]_1/2[Zr₂(HPO₄)(PO₄)₂F] · nH₂O ( I : am = N,N‐dimethylethylenediamine, n = 0,5; II : am = N,N‐dimethyl‐1,3‐diaminopropane, n = 0) adopting the ZrPOF‐1 structure type have been synthesized under hydrothermal conditions. In contrast to the monoclinic ZrPOF‐1, both compounds crystallize in the space group P 1 with a = 6.611(3), b = 9.109(4), c = 11.560(5) Å, α = 85.62(4), β = 89.60(4), γ = 70.57(4)° in I , and a = 6.616(2), b = 9.045(3), c = 11.565(4) Å, α = 85.26(4), β = 88.86(4), γ = 71.46(4)° in II . Compound III (am = ethylenediamine, n = 0) has been obtained by dehydration of ZrPOF‐1 and occurs in the space group P1 with a = 6.605(2), b = 8.787(3), c = 11.499(5) Å, α = 93.07(4), β = 90.42(4) and γ = 104.66(4)°. The structural motifs of the frameworks of the three compounds have much in common. The template and the PO₃OH tetrahedra in I and II are disordered. Differences in the water content in both compounds are due to differences in the chain lengths of the amines. The absence of crystal water in compound III breaks the template disordering which is present in ZrPOF‐1. The rotation of the PO₃OH tetrahedra in II and III compared with I and ZrPOF‐1 is discussed in regard with the absence of stabilizing H‐bridges in the former compounds.