422 research outputs found
The Crystal Structure of the Cesium Molybdenum Bronze CS0.14MoO3
No full textJournal of Solid State Chemistry
Volume 104, Issue 2, June 1993, Pages 209-214
The Crystal Structure of the Cesium Molybdenum Bronze CS0.14MoO3 (Article)
Depero, L.E.,
Zocchi, M.,
Zocchi, F.,
Demartin, F.
Dipartimento di Ingegneria Meccanica dell'Università, Via Branze, 25123 Brescia, Italy; IMAI-CNR Area della Ricerca di Roma, 00016 Monterotondo Stazione, Rome, Italy and Istituto di Chimica Strutturistica Inorganica dell'Università degli Studi, Via G. Venezian 21, 20133, Milan, Italy
Abstract
The crystal of the title compound is hexagonal, space group P 63/m, with a = 10.620(9), c = 3.722(2) Å, and Z = 6. Couples of MoO6 distorted octahedra, linked by edges, constitute, by repetitive edge sharing along the c axis, ribbons kept together in bundles by lateral corner sharing. These bundles, by being packed together, generate tunnels where delocalized Cs atoms are inserted. The results confirmed the previously found correlation between the Mo oxidation state and the distortion of the coordination "octahedra" and allow one to extend the correlation to the possible conduction properties of the title compound and to those of structurally related oxides and bronzes. © 1993 Academic Press. All rights reserved.
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ISSN: 00224596 CODEN: JSSCBSource Type: Journal Original language: English
DOI: 10.1006/jssc.1993.1155Document Type: Article
Depero, L.E.; Dipartimento di Ingegneria Meccanica dell'Università, Via Branze, 25123 Brescia, Italy; IMAI-CNR Area della Ricerca di Roma, 00016 Monterotondo Stazione, Rome, Italy and Istituto di Chimica Strutturistica Inorganica dell'Università degli Studi, Via G. Venezian 21, 20133, Milan, Italy,
© Copyright 2008 Elsevier B.V., All rights reserved
F. Cristiani, F. Demartin, F. A. Devillanova, F. Isaia, V. Lippolis, G. Verani Spectroscopic studies of charge-transfer complexes of 1,4,7-trithiacyclononane with diiodine.
No full text1,4,7-Trithiacyclononane ([9]aneS3) reacts with molecular diiodine in CH2Cl2 to form a 1:1 adduct. The formation constant and the thermodynamic parameters of this adduct have been determined by UV-visible spectra of several solutions at the temperatures of 15, 20, 25, 30, and 35-degrees-C. The C-13 NMR spectra show that adducts with higher ligand/diiodine molar ratios are formed. Two neutral charge-transfer molecular compounds having formula 2[9]aneS3 . 4I2 (I) and [9]aneS3 . 3I2 . (II) have been obtained as crystals. The crystals of I are triclinic (a = 8.498(2) angstrom, b = 13.984(4) angstrom, c = 14.898(6) angstrom, alpha = 65.57(2)degrees, beta = 89.19(2)degrees, gamma = 81.26(2)degrees, Z = 2, space group P1BAR; R = 0.025) and contain units formed by two [9]aneS3 molecules connected by a diiodine molecule; one [9]aneS3 binds two other diiodine molecules, while the second binds only one other diiodine molecule. The crystals of II are monoclinic (a = 13.810(2) angstrom, b = 9.829(4) angstrom, c = 16.198(6) angstrom, beta = 113.41(2)degrees, Z = 4, space group P2(1)/c; R = 0.019) and contain molecules of [9]aneS3 binding three diiodine molecules. FT-Raman spectra in the characteristic nu(I-I) region, carried out on the solid adducts, are discussed in comparison with the structural parameters
Synthesis of two novel pentanuclear rhodium clusters bearing the alkyl-like ligands -CH2COOMe and -CH2CN. X-ray structure of [PPh4]2[Rh5(μ-CO)6(CO)8(CH2CN)]
No full textThe reaction of [PPh4][Rh(CO)4] (1) under CO with BrCH2COOMe or BrCH2CN in a 5:3 molar ratio gave high yields of the two novel clusters [PPh4]2[Rh5(CO)14-(CH2COOMe)] (3a) and [PPh4]2[Rh5(CO)14(CH2CN)] (3b), respectively, which appear to be the first examples of rhodium clusters bearing an alkyl-like ligand. The first step of the reaction is the rapid formation of [PPh4]-[RhBr(CO)2(CH2R)] (R = COOMe (2a), CN (2b)), which further react, much more slowly, with an excess of [Rh-(CO)4]-to yield the cluster compounds. 3a,b are indefinitely stable in the solid state under CO atmosphere. Crystals of 3b suitable for an X-ray diffraction study could be obtained. 3b is monoclinic, space group P2(1)/c with a = 12.488 (3) angstrom, b = 43.585 (9) angstrom, c = 23.222 (8) angstrom, beta = 91.46 (4)-degrees, Z = 8, and R = 0.037 for 8489 reflections having I greater-than-or-equal-to 3-sigma(I). The [Rh5(CO)14(CH2CN)]- anion contains an elongated trigonal-bipyramidal metallic framework bearing eight terminal and six edge-bridging carbonyls; the alkyl-like substituent is bonded to an apical Rh atom
Knabsibfite, K3Na4[SiF6]3[BF4], a new hexafluorosilicate from La Fossa crater, Vulcano, Aeolian islands, Italy
No full textKnasibfite, ideally K3Na4[SiF6]3[BF4], is a newly discovered mineral species that can be considered a potassium and sodium
hexafluorosilicate–tetrafluoroborate. It occurs in an altered pyroclastic breccia associated with hieratite, avogadrite and demartinite
in a low-temperature fumarole at the rim of La Fossa crater, Vulcano Island, Aeolian Archipelago, Sicily, Italy. The mineral
is orthorhombic, space group Imm2, with a 5.522(1), b 17.106(3), c 9.175(2) Å, V 866.7(3) Å3, Z = 2. The crystals are colorless,
prismatic up to 0.1 mm, most commonly showing the forms {001}, {100}, {010}, {110}, {011} and {101}. The mean analytical
results are: K 16.78, Na 13.14, Si 11.36, F 57.83, B 1.50, for a total of 100.61 wt%. The boron content has been estimated from
results of the crystal-structure analysis. The empirical formula (based on 33 apfu) is: K3.09Na4.11Si2.91B1.00F21.89; the simplified
formula is K3Na4[SiF6]3[BF4], which requires: K 16.24, Na 12.73, Si 11.67, F 57.87, B 1.50, for a total of 100.00 wt%. The crystal
structure has been refined to a final R index of 0.0272 for 660 observed reflections. The asymmetric unit contains two twelvecoordinated
independent K+ ions, located on m.. and on mm2 sites, respectively [K–F distances in the range 2.756(3)–3.332(2) Å],
two independent Na+ ions, of which one is nine-coordinated [Na–F distances in the range 2.254(5)–2.949(3) Å], and the other one
displays instead octahedral coordination [Na–F distances in the range 2.224(3)–2.387(3) Å]. There are also two crystallographically
independent octahedral SiF62– anions with Si–F distances in the range 1.640(6)–1.684(4) Å, and a tetrahedral BF4– anion,
with B–F distances ranging from 1.385(6) to 1.386(7) Å. The calculated density is 2.77 g/cm3, the measured density is 2.75(1)
g/cm3. The mineral is optically nearly isotropic, with n = 1.32(1). The strongest six lines in the X-ray powder-diffraction pattern
[dobs in Å(I)hkl] are: 4.044(100)(022), 8.558(50)(020), 2.280(50)(222), 3.175(30)(141), 8.107(25)(011) and 2.094(25)(251). The
name reflects its chemical composition
SYNTHESIS AND CRYSTAL-STRUCTURE OF [PPH4]2[IR4(CO)10(CH2COOME)2] AND [PPH4][IR4(CO)11(CH2COOME)] - 1ST EXAMPLES OF IRIDIUM CLUSTERS BEARING AN ALKYL-LIKE LIGAND
No full textThe reaction of Na[Ir(CO)4] ([Na]1) with given amounts of BrCH2COOMe in THF, followed by treatment with PPh4Cl, gave high yields of the two novel clusters [PPh4]2[Ir4(CO)10(CH2COOMe)2] ([PPh4](2)2) and [PPh4] [Ir4(CO)11(CH2COOMe)] ([PPh4]3). The reaction takes place in two steps; the first compound formed is 2, which then reacts, in a slower reaction, with excess BrCH2COOMe to afford 3. To the best of our knowledge, 2 and 3 are among the first examples of clusters bearing an alkyl or alkyl-like substituent. X-ray diffraction analysis of the clusters was carried out on crystals obtained by using PPh4+ as a countercation. Compound [PPh4](2)2 is triclinic, space group P1BAR, with a = 11.163 (2) angstrom, b = 12.807 (2) angstrom, c = 22.849 (3) angstrom, alpha = 84.76 (1)-degrees, beta = 88.76 (1)-degrees, gamma = 73.53 (1)-degrees, Z = 2, R = 0.034, and R(w) = 0.042 for 6373 independent reflections with I > 3-sigma(I). Compound [PPh4]3 is monoclinic, space group P2(1)/c, with a = 13.155 (4) angstrom, b = 24.593 (5) angstrom, c = 38.401 (8) angstrom, beta = 91.00 (3)-degrees, Z = 12, R = 0.065, and R(w) = 0.069 for 5227 independent reflections with I > 3-sigma(I). Both anions contain a tetrahedron of iridium atoms with three bridging CO ligands around a triangular basal face of the metal tetrahedron, the alkyl-like substituents being axially bonded to the iridium atoms of this face. The reactivity of the sodium salt of [Ir(CO)4]- with BrCH2COOMe was quite different from that, already reported by us, of the same anion with PPN+ (PPN+ = (PPh3)2N+) as a countercation. This latter reaction forms only mononuclear species. The possible role of Na+ in the formation of the clusters is discussed
Aluminopyracmonite, (NH4)3Al(SO4)3, a new ammonium aluminium sulfate from La Fossa crater, Vulcano, Aeolian Islands, Italy
No full textThe new mineral aluminopyracmonite, ideally (NH4)3Al(SO4)3, was found in a medium-temperature (~250oC) intracrater active fumarole at La Fossa crater, Vulcano, Aeolian Islands, Sicily, Italy. It occurs on a pyroclastic breccia as colourless to white prismatic crystals up to 0.2 mm long, in
association with adranosite, mascagnite, alunite and salammoniac. The mineral is identical to the
synthetic compound (NH4)3Al(SO4)3. It is trigonal, space group: R-3 (no. 148) with a = 15.0324(8), c = 8.8776(5) A, V = 1737.3(2) A^3 and Z = 6. The six strongest reflections in the X-ray powder diffraction pattern are: [dobs in A (I)(hkl)] 3.336(100)(131), 7.469(62)(1 1 0), 3.288(60)(122), 4.289(45)(-231), 2.824(29)(-351), 4.187(27)(012). The empirical formula based on 12 anions is [(NH4)2.89K0.10]S2.99(Al1.18Fe0.01)S1.19S2.91O12, and the simplified formula (NH4,K)3Al(SO4)3. The
measured density is 2.12(1) g/cm3, calculated density 2.143 g/cm3. The mineral is uniaxial(–) with omega =
1.545(3) and epsilon = 1.532(3) (lambda = 589 nm). Using single-crystal diffraction data, the structure was refined to a final R(F) = 0.0258 for 998 independent observed reflections [I > 2s(I)]. In spite of having unitcell
parameters comparable with those of pyracmonite, the two minerals are not isostructural; the difference is related to a disordered conformation of the sulfate anions about the two independent Al3+ ions in aluminopyracmonite
MECHANISTIC STUDY OF THE CARBONYLATION OF NITROBENZENE CATALYZED BY THE [RH(CO)4]- NITROGEN BASE SYSTEM - X-RAY STRUCTURE OF [PPN][RH(CO)2ON(C6H3CL2)C(O)O]
No full text[PPN] [Rh(CO)4] (1) reacts with ArNO2 or ArNO to yield the same product (Ar = Ph, 2; Ar = 3,4-Cl2-C6H3, 3). The reaction of 1 with nitrosoarenes also produces the corresponding azoxyarenes. The product was structurally characterized in the case of Ar = 3,4-dichlorophenyl and was shown to be [PPN][Rh(CO)2ON(C6H3Cl2)C(O)O] (3). Crystal data for 3: C45H33Cl2N2O5P2Rh.C4H8O, M(r) = 989.64, triclinic, space group P1BAR (No. 2), a = 10.798(4) angstrom, b = 9.889(6) angstrom, c = 21.648(6) angstrom, a = 89.77(1)degrees, beta = 96.00(1)degrees, gamma = 92.71(1)degrees, V = 2296(2) angstrom2, Z = 2, D()c = 1.431 g cm-3, Mo Kalpha radiation (lambda = 0.710 73 angstrom), mu(Mo Kalpha) = 6.00 cm-1, R = 0.037 (R(w) = 0.047) for 5299 independent reflections having I > 3sigma(I). Both of the reactions proceed through electron transfer to the nitroso or nitro derivative. Reaction of 2 and 3 with MeOH and CO produced the corresponding amine or the methyl carbamate, depending on the experimental conditions. The reaction of 3 with MeOH/CO was faster in the presence of nitrogen bases, and aniline was shown to be an intermediate in the synthesis of the carbamate. When the same reaction was performed in the presence of a large excess of nitrosobenzene, the two isomeric mixed azoxybenzenes 3,4-Cl2-C6H3N(O)=NPh and 3,4-Cl2-C6H3N=N(O)Ph were the largely dominant products, which strongly suggests the intermediate formation of a nitrene complex
Use of amido Grignard reagents in inorganic chemistry : Synthesis and crystal structure of anti-[Pd(Cl)(py)(mu-2,6-Pri2C6H3NH)](2)
Get PDFTreating a pyridine (py) solution of PdCl2(py)(2) with a tetrahydrofuran or diethyl ether solution of the amido Grignard reagent 2,6-(Pr2C6H3NH)-C-1(MgCl) afforded a dimeric palladium complex, containing two bridging amido groups, which has been structurally characterised
THE CRYSTAL STRUCTURE OF CERVANDONITE-(Ce), AN INTERESTING EXAMPLE OF As3+ → Si DIADOCHY
No full textCervandonite-(Ce), a unique arsenosilicate from Alpine fissures at Pizzo Cervandone (Scherbadung) in the Central Alps between the Binn Valley (CH) and Ossola (I), has proven to be a problem in view of the extreme scarcity of single crystals suitable for the determination of its complex structure. The monoclinic supercell (Z = 6) originally described by the discoverers is
confirmed; we have established the crystal structure of a trigonal subcell, with space group R3m and a 6.508(1), c 18.520(3) Å, V 679.4(2) Å3 and Z = 3, to a final R(F) = 0.0380 for 441 observed independent reflections [I > 2s(I)]. The mechanism of the very unusual As3+ ! Si (not As5+ ! Si) diadochy is accounted for by considering the presence in two different sites of sorosilicate anions Si2O76–, which are statistically replaced by arsenite [AsO33–] anions and minor amounts of OH–; the positions of
the oxygen atoms common to these anions are the same. The asymmetric unit also contains one eight-coordinated atomic site occupied by Ce and other REE lying on the three-fold axis; a bipyramidal six-coordinated site (of symmetry .m) occupied by Fe, Ti, or Al also is present. The originally proposed chemical formula (Ce,Nd,La)(Fe3+,Fe2+,Ti4+,Al)3SiAs(Si,As)O13 is accordingly
revised to (Ce,Nd,La) Fe3+,Fe2+,Ti4+,Al)3O2(Si2O7)1–x+y (AsO3)1+x–y(OH)3x–3y, where x and y are 0.47 and 0.31, respectively, in the sample here examined
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