A one-dimensional azido-bridged manganese(III) complex with bidentate Schiff base: Crystal structure and magnetic properties

The synthesis, structural characterization, and magnetic behavior of a novel one-dimensional azido-bridged manganese(III) complex of formula [Mn(L)₂N₃] (1) is reported, where HL is the bidentate Schiff base obtained from the condensation of salicylaldehyde with 4-methoxy aniline. Complex 1 crystallizes in the monoclinic system, space group P2₁/n, with a=11.743(4) Å, b=24.986(9) Å, c=13.081(5) Å, β=95.387(7)° and Z=2. The complex is of one-dimensional chain structure with single end-to-end azido bridges and the manganese(III) ion has an elongated octahedral geometry. Magnetic studies show that the weak antiferromagnetic interaction is mediated by the single end-to-end azido bridge with the exchange parameter J=−5.84 cm⁻¹.     

Synthesis and crystal structure of a new open-framework iron phosphate (NH4)4Fe3(OH)2F2[H3(PO4)4]: Novel linear trimer of corner-sharing Fe(III) octahedra

A new iron phosphate (NH₄)₄Fe₃(OH)₂F₂[H₃(PO₄)₄] has been synthesized hydrothermally at HF concentrations from 0.5 to 1.2 mL. Single-crystal X-ray diffraction analysis reveals its three-dimensional open-framework structure (monoclinic, space group P2₁/n (No. 14), a=6.2614(13) Å, b=9.844(2) Å, c=14.271(3) Å, β=92.11(1)°, V=879.0(3) Å³). This structure is built from isolated linear trimers of corner-sharing Fe(III) octahedra, which are linked by (PO₄) groups to form ten-membered-ring channels along [1 0 0]. This isolated, linear trimer of corner-sharing Fe(III) octahedra, [(FeO₄)₃(OH)₂F₂], is new and adds to the diverse linkages of Fe polyhedra as secondary building units in iron phosphates. The trivalent iron at octahedral sites for the title compound has been confirmed by synchrotron Fe K-edge XANES spectra and magnetic measurements. Magnetic measurements also show that this compound exhibit a strong antiferromagnetic exchange below T_N=17 K, consistent with superexchange interactions expected for the linear trimer of ferric octahedra with the Fe-F-Fe angle of 132.5°.     

Study on carbon-hydrogen activation of ketones by Gold(III) complexes and the synthesis and characterization of two ketonylgold(III) complexes

The acetonylgold(III) compound [Au(ppy)(CH₂COCH₃)Cl] (1) (ppy = 2-phenylpyridine) was unexpectedly obtained during the crystallization process of Au(III) lactate complex [Au(ppy)(CH₃CHOHCOO⁻)Cl]. This new structure prompted us to further study the role of Au(III) complexes on the carbon-hydrogen activation of ketones. Complex [Au(ppy)(CH₂COCH₃)NO₃] (2) was synthesized by reacting [Au(ppy)(NO₃)₂] with acetone while the ketonyl Au(III) complex [Au(apd)Cl₂] (3) (Hapd = 2-acetylpyridine) was obtained through carbon-hydrogen bond activation of the acetyl group. The crystal structures of 1 and 2 have common features: a square-planar Au(III) centre coordinated by one five-membered chelate ring, one acetonyl ligand and one anion (chloride or nitrate). Both structures show that carbon-hydrogen activation of acetone by 2-phenylpyridine-Au(III) complexes leads to the formation of acetonyl-Au(III) complexes. The Au-CH₂ bond lengths (2.067(7) Å, 1 and 2.059(5) Å, 2) are similar to each other but longer than the Au-C (phenyl) bond lengths. The two softest ligands (carbanion) are also cis to each other in the thermodynamically most stable isomer. In complex 3, the σ-bonded acetyl group is confirmed by ¹³C DEPT NMR spectroscopy.     

Structure and redox behavior of Ru(II)-diene complexes

A series of Ru(acac)₂(η⁴-diene) complexes containing cis- and trans-diene coordination have been investigated by cyclic voltammetry to correlate structural bonding and conformation patterns of diene ligands with redox behaviors. The solid-state structure of Ru(acac)₂(2,3-dimethyl-1,3-butadiene) has been determined by single crystal X-ray diffraction methods. Ru(acac)₂(2,3-dimethyl-1,3-butadiene) crystallizes in the monoclinic space group C2/c with a = 12.368(2) Å, b = 17.0600(2) Å, c = 16.0110(2) Å, β = 98.4405(10)° and V = 3341.38(10) ų for Z = 8. A structural comparison between several Ru-trans-η⁴-diene complexes and Ru-η⁴-1,3-cyclohexadiene revealed no difference in the Ru-C(diene) bond distances. However, through cyclic voltammetry experiments these species demonstrated different redox behavior, as function of the coordinated diene ligand.     

Synthesis of chloroantimonates(III) with selected organic cations. X-ray studies of phase transition in ferroelectric tris(trimethylammonium) nonachlorodiantimonate(III) at 125 K

The dependence of molar ratio of reactants on the formula, crystal structure and physicochemical properties of chloroantimonates(III) with different organic cations was studied. It was proved, that the compounds show preferences in crystallization of one product. The changes of the molar ratio of substrates lead to the corresponding changes of these components in crystallized products. The structure of ferroelectric chloroantimonate(III), [(CH₃)₃NH]₃[Sb₂Cl₉], was determined at 165 and 95 K. It crystallizes in monoclinic space group Pc: a=9.9612(11), b=9.0714(8), c=15.1807(14) Å, β=90.086(8)°, R₁=0.0202, wR₂=0.0405 and a=9.9138(10), b=9.0783(7), c=15.1299(14) Å, β=90.026(8)°, R₁=0.0163, wR₂=0.0356 at 165 and 95 K, respectively. At both temperatures the crystal is built of polyanionic layers and trimethylammonium cations. They are bound together by the system of hydrogen bonds. The molecular motions of the organic cations are gradually frozen with decreasing temperature. At 165 K all cations are ordered. The non-structural ferro-ferroelectric phase transition at 125 K is associated with changes in the dynamics of trimethylammonium cations.     

Lanthanide N,N′-piperazine-bis(methylenephosphonates) (Ln=La, Ce, Nd) that display flexible frameworks, reversible hydration and cation exchange

Hydrothermal syntheses of lanthanide bisphosphonate metal organic frameworks comprising the light lanthanides lanthanum, cerium and neodymium and N,N′-piperazine bis(methylenephosphonic acid) (H₂L(1) and its 2-methyl and 2,5-dimethyl derivatives (H₂L(2) and H₂L(3)) gives three new structure types. At elevated starting pH (ca. 5 and above) syntheses give ‘type I’ materials with all metals and acids of the study (MLnLxH₂O, M=Na, K, Cs; Ln=La, Ce, Nd; x≈4: KCeL(1)·4H₂O, C2/c, a=23.5864(2) Å, b=12.1186(2) Å, c=5.6613(2) Å, β=93.040(2)°). The framework of structure type I shows considerable flexibility as the ligand is changed, due mainly to rotation around the -N-CH₂- bond of the linker in response to steric considerations. Type I materials demonstrate cation exchange and dehydration and rehydration behaviour. Upon dehydration of KCeL·4H₂O, the space group changes to P2₁/n, a=21.8361(12) Å, b=9.3519(4) Å, c=5.5629(3) Å, β=96.560(4)°, as a result of a change of the piperazine ring from chair to boat configuration. When syntheses are performed at lower pH, two other structure types crystallise. With the ‘non-methyl’ ligand 1, type II materials result (LnL(1)H₂L(1)·4.5H₂O: Ln=La, P−1, a=5.7630(13) Å, b=10.213(2) Å, c=11.649(2) Å, α=84.242(2)°, β=89.051(2)°, γ=82.876(2)°) in which one half of the ligands coordinate via the piperazine nitrogen atoms. With the 2-methyl ligand, structure type III crystallises (LnHL(2)·4H₂O: Ln=Nd, Ce, P2₁/c, a=5.7540(9) Å, b=14.1259(18) Å, c=21.156(5) Å, β=90.14(2)°) due to unfavourable steric interactions of the methyl group in structure type II.     

Synthesis and structural investigation of the compounds containing HF2 anions: Ca(HF2)2, Ba4F4(HF2)(PF6)3 and Pb2F2(HF2)(PF6)

Three new compounds Ca(HF₂)₂, Ba₄F₄(HF₂)(PF₆)₃ and Pb₂F₂(HF₂)(PF₆) were obtained in the system metal(II) fluoride and anhydrous HF (aHF) acidified with excessive PF₅. The obtained polymeric solids are slightly soluble in aHF and they crystallize out of their aHF solutions. Ca(HF₂)₂ was prepared by simply dissolving CaF₂ in a neutral aHF. It represents the second known compound with homoleptic HF environment of the central atom besides Ba(H₃F₄)₂. The compounds Ba₄F₄(HF₂)(PF₆)₃ and Pb₂F₂(HF₂)(PF₆) represent two additional examples of the formation of a polymeric zigzag ladder or ribbon composed of metal cation and fluoride anion (MF⁺)_n besides PbF(AsF₆), the first isolated compound with such zigzag ladder. The obtained new compounds were characterized by X-ray single crystal diffraction method and partly by Raman spectroscopy. Ba₄F₄(HF₂)(PF₆)₃ crystallizes in a triclinic space group P1¯ with a=4.5870(2) Å, b=8.8327(3) Å, c=11.2489(3) Å, α=67.758(9)°, β=84.722(12), γ=78.283(12)°, V=413.00(3) Å³ at 200 K, Z=1 and R=0.0588. Pb₂F₂(HF₂)(PF₆) at 200 K: space group P1¯, a=4.5722(19) Å, b=4.763(2) Å, c=8.818(4) Å, α=86.967(10)°, β=76.774(10)°, γ=83.230(12)°, V=185.55(14) ų, Z=1 and R=0.0937. Pb₂F₂(HF₂)(PF₆) at 293 K: space group P1¯, a=4.586(2) Å, b=4.781(3) Å, c=8.831(5) Å, α=87.106(13)°, β=76.830(13)°, γ=83.531(11)°, V=187.27(18) Å³, Z=1 and R=0.072. Ca(HF₂)₂ crystallizes in an orthorhombic Fddd space group with a=5.5709(6) Å, b=10.1111(9) Å, c=10.5945(10) Å, V=596.77(10) Å³ at 200 K, Z=8 and R=0.028.     

Synthesis and characterization of organic-inorganic hybrid compounds with a pillared layer structure: Ga2(4,4′-bpy)(XO4)2 (X=P, As)

Two organic-inorganic hybrid compounds, Ga₂(4,4′-bpy)(PO₄)₂, 1, and Ga₂(4,4′-bpy)(AsO₄)₂, 2, have been synthesized under hydrothermal conditions and structurally characterized by single-crystal X-ray diffraction. The two compounds are isostructural and crystallize in the triclinic space group (No. 2) with a=4.9723(9) Å, b=5.770(1) Å, c=11.812(2) Å, α=78.268(3)°, β=89.159(3)° γ=88.344(3)°, V=331.7(2) Å³, Z=1, and R1=0.0377 for 1, and a=5.1111(7) Å, b=5.9327(8) Å, c=11.788(2) Å, α=79.497(2)°, β=88.870(2)°, γ=88.784(2)°, V=351.3(2) Å³, and R1=0.0264 for 2. The structure consists of neutral sheets of GaXO₄ (X=P or As) which are pillared through 4,4′-bipyridine ligands. Each oxide layer, which is formed only by four-membered rings, is constructed from corner-sharing GaO₄N trigonal bipyramids and XO₄ tetrahedra. The title compounds are two of the few examples in which the gallium atoms are exclusively five-coordinate.     

New binuclear vanadium(III) and (IV) squarate species: synthesis, structure and characterization of [V(OH)(H2O)2(C4O4)]2·2H2O and (NH4)[(VO)2(OH)(C4O4)2(H2O)3]·3H2O

Two new vanadium squarates have been synthesized, characterized by infrared and thermal behavior and their structures determined by single crystal X-ray diffraction. Both structures are made of discrete, binuclear vanadium entity but in 1, [V(OH)(H₂O)₂(C₄O₄)]₂·2H₂O the vanadium atom is trivalent and the entity is neutral while in 2, (NH₄)[(VO)₂(OH)(C₄O₄)₂(H₂O)₃]·3H₂O, the vanadium atom is tetravalent and the entity is negatively charged, balanced by the presence of one ammonium ion. Both molecular anions are bridged by two terminal μ₂ squarate ligands. 1 crystallizes in the triclinic system, space group P-1, with lattice constants a=7.5112(10) Å, b=7.5603(8) Å, c=8.2185(8) Å, α=106.904(8)°, β=94.510(10)°, γ=113.984(9)° while 2 crystallizes in the monoclinic system, space group C2/c, with a=14.9340(15) Å, b=6.4900(9) Å, c=17.9590(19) Å and β=97.927(12)°. From the magnetic point of view, V(III) binuclear species show ferromagnetic interactions at low temperatures. However, no anomalies pointing to magnetic ordering are observed down to 2 K.     

Synthesis of tungsten compounds with Schiff base ligands prepared from ferrocenecarboxaldehyde: Observation of the migration of an imine double bond

The one-pot reactions of ferrocenecarboxaldehyde, W(CO)₄(pip)₂ (pip = piperidine) and either 2-(aminomethyl)pyridine or 2-(2-aminoethyl)pyridine lead to clean formation of pyridine imine products W(CO)₄(η²-NC₅H₄CHNCH₂C₅H₄FeCp) (1) and W(CO)₄(η²-NC₅H₄C₂H₄NCHC₅H₄FeCp) (2), respectively. Crystal structures of the two compounds show that in 1 the imine double bond has migrated so that it is conjugated with the pyridine ring while in 2 the imine double bond remains conjugated with the cyclopentadienyl ring. This finding is reinforced by a comparison of dihedral angles in each molecule. IR, NMR and electronic spectra each highlight the differences between the two compounds. Crystal data for C₂₁H₁₆FeN₂O₄W (1): monoclinic P2(1)/c, a = 12.768(2) Å, b = 13.593(2) Å, c = 12.981(2) Å, β = 119.46°, V = 1961.6(4) Å³, Z = 4; C₂₂H₁₈FeN₂O₄W (2): monoclinic P2(1)/c, a = 16.759(1) Å, b = 8.8612(7) Å, c = 13.802(1) Å, β = 95.998(1)°, V = 2038.4(3) Å³, Z = 4.     

Low-dimensional compounds containing cyanido groups. XXI. Crystal structure, spectroscopic, thermal and magnetic properties of two polymorphous modifications of [Cu(men)2Pt(CN)4]n complex (men = N-methyl-1,2-diaminoethane)

Violet (1) and blue (2) polymorphous modifications of [Cu(men)₂Pt(CN)₄]_n (men = N-methyl-1,2-diaminoethane) have been prepared and investigated by IR and UV-vis spectroscopy, thermal analysis, measurement of magnetic data and X-ray structural analysis. Both modifications are formed by similar but differently packed zigzag chains, which consist of [Cu(men)₂]²⁺ moieties bridged by two trans arranged cyanido groups of [Pt(CN)₄]²⁻ units. The Cu(II) atoms in both structures are hexacoordinated by four nitrogen atoms in the equatorial plane from two molecules of bidentate men ligands with the average Cu-N(Me) and Cu-N(H₂) bond lengths of 2.046(8) and 2.008(8) Å, respectively, and by two nitrogen atoms from bridging cyanido groups in the axial positions at average distance of 2.50(7) Å. Broad nearly symmetric bands observed in the UV-vis spectra of 1 and 2 of ²B_1g → ²E_g transitions are consistent with a deformed octahedral coordination of the CuN₆ chromophoric groups. One and two ν(CN) absorption bands observed in the IR spectra of 1 and 2, respectively, are in agreement with different local symmetries of [Pt(CN)₄]²⁻ units and different Cu-N(cyanido) bond lengths in these polymorphs and are subject of discussion on the spectral-structural correlations in 1D compounds. The complexes are stable up to 238 °C when their two-stage thermal decompositions start and ending up with a mixture of CuO and metallic Pt as the most probable final thermal decomposition products. The temperature dependence of the magnetic susceptibility suggests the presence of a weak antiferromagnetic exchange coupling between Cu(II) atoms in 1, J/hc = −0.17 cm⁻¹ and in 2, J/hc = −1.3 cm⁻¹.     

The structures of (phenylato)(N-2-thiophenecarboxamido-meso-tetraphenylporphyrinato)mercury(II) and bisphenylmercury(II) complex of 21-(4-tert-butyl-benzenesulfonamido)-5,10,15,20-tetraphenylporphyrin

The reaction of PhHgOAc with N-NHCO-2-C₄H₃S-Htpp (5) and N-p-HNSO2C6H4^tBu-Htpp (4) gave a mercury (II) complex of (phenylato) (N-2-thiophenecarboxamido-meso-tetra phenylporphyrinato)mercury(II) 1.5 methylene chloride solvate [HgPh(N-NHCO-2-C₄H₃S-tpp) · CH₂Cl₂ · 0.5C₆H₁₄;  6 · CH₂Cl₂ · 0.5C₆H₁₄] and a bismercury complex of bisphenylmercury(II) complex of 21-(4-tert-butyl-benzenesulfonamido)-5,10,15,20-tetraphenylporphyrin, [(HgPh)2(N-p-NSO₂C₆H₄^tBu-tpp); 7], respectively. The crystal structures of 6 · CH₂Cl₂ · 0.5C₆H₁₄ and 7 were determined. The coordination sphere around Hg(1) in 6 · CH₂Cl₂ · 0.5C₆H₁₄ and Hg(2) in 7 is a sitting-atop derivative with a seesaw geometry, whereas for the Hg(1) in 7, it is a linear coordination geometry. Both Hg(1) in 6 · CH₂Cl₂ · 0.5C₆H₁₄ and Hg(2) in 7 acquire 4-coordination with four strong bonds [Hg(1)–N(1) = 2.586(3) Å, Hg(1)–N(2) = 2.118(3) Å, Hg(1)–N(3) = 2.625(3) Å, and Hg(1)–C(50) = 2.049(4) Å for 6 · CH₂Cl₂ · 0.5C₆H₁₄; Hg(2)–N(1) = 2.566(6) Å, Hg(2)–N(2) = 2.155(6) Å, Hg(2)–N() = 2.583(6) Å, and Hg(2)–C(61) = 2.064(7) Å for 7]. The plane of the three pyrrole nitrogen atoms [i.e., N(1)–N(3)] strongly bonded to Hg(1) in 6 · CH₂Cl₂ · 0.5C₆H₁₄ and to Hg(2) in 7 is adopted as a reference plane 3N. For the Hg²⁺ complex in 6 · CH₂Cl₂ · 0.5C₆H₁₄, the pyrrole nitrogen bonded to the 2-thiophenecarboxamido ligand lies in a plane with a dihedral angle of 33.4° with respect to the 3N plane, but for the bismercury(II) complex in 7, the corresponding dihedral angle for the pyrrole nitrogen bonded to the NSO₂C₆H₄^tBu group is found to be 42.9°. In the former complex, Hg(1)²⁺ and N(5) are located on different sides at 1.47 and −1.29 Å from its 3N plane, and in the latter one, Hg(2)²⁺ and N(5) are also located on different sides at −1.49 and 1.36 Å form its 3N plane. The Hg(1)?Hg(2) distance in 7 is 3.622(6) Å. Hence, no metallophilic Hg(II)?Hg(II) interaction may be anticipated. NOE difference spectroscopy, HMQC and HMBC were employed to unambiguous assignment for the ¹H and ¹³C NMR resonances of 6 · CH₂Cl₂ ·  0.5C₆H₁₄ in CD₂Cl₂ and 7 in CDCl₃ at 20 °C. The ¹⁹⁹Hg chemical shift δ for a 0.05 M solution of 7 in CDCl₃ solution is observed at −1074 ppm for Hg(2) nucleus with a coordination number of four and at −1191 ppm for Hg(1) nucleus with a coordination number of two. The former resonance is consistent with that chemical shift for a 0.01 M solution of 6 in CD₂Cl₂ having observed at −1108 ppm for Hg(1) nucleus with a coordination number of four.     

Synthesis, crystal structure and magnetic characterization of metal(II) coordination polymers based on 2-carboxyethylphosphonic acid and 1,10-phenanthroline (metal=Cu, Co, Cd)

Three non-isostructural metal(II) coordination polymers (metal=copper, cobalt, cadmium) were synthesized under the same mild hydrothermal conditions (T=408 K) by mixture of the corresponding metal acetate with 2-carboxyethylphosphonic acid and 1,10-phenanthroline (1:1:1 M ratio) and their structures were determined by single-crystal X-ray diffraction. Cu₂(HO₃PCH₂CH₂COO)₂(C₁₂H₈N₂)₂(H₂O)₂ and Cd₂(HO₃PCH₂CH₂COO)₂(C₁₂H₈N₂)₂ are triclinic (space group P-1) with a=7.908(5) Å, b=10.373(5) Å, c=11.515(5) Å, α=111.683(5)°, β=95.801(5)°, γ=110.212(5)° (T=120 K), and a=8.162(5) Å, b=9.500(5) Å, c=11.148(5) Å, α=102.623(5)°, β=98.607(5)°, γ=113.004(5)° (T=293 K), respectively. In contrast, [Co₂(HO₃PCH₂CH₂COO)₂(C₁₂H₈N₂)₂(μ-OH₂)](H₂O) is orthorhombic (space group Pbcn) with a=21.1057(2) Å, b=9.8231(1) Å, c=15.4251(1) Å (T=120 K). For these three compounds, structural features, including H-bond network and the π-π stacking interactions, and thermal stability are reported and discussed. None of the materials present a long-range magnetic order in the range of temperatures investigated from 300 K down to 1.8 K.     

Crystal chemistry of M[PO2(OH)2]2·2H2O compounds (M=Mg, Mn, Fe, Co, Ni, Zn, Cd): Structural investigation of the Ni, Zn and Cd salts

The compounds M[PO₂(OH)₂]₂·2H₂O (M=Mg, Mn, Fe, Co, Ni, Zn, Cd) were prepared from super-saturated aqueous solutions at room temperature. Single-crystal X-ray structure investigations of members with M=Ni, Zn, Cd were performed at 295 and 120 K. The space-group symmetry is P2₁/n, Z=2. The unit-cell parameters are at 295/120 K for M=Ni: a=7.240(2)/7.202(2), b=9.794(2)/9.799(2), c=5.313(1)/5.285(1) Å, β=94.81(1)/94.38(1)°, V=375.4/371.9 Å³; M=Zn: a=7.263(2)/7.221(2), b=9.893(2)/9.899(3), c=5.328(1)/5.296(2) Å, β=94.79(1)/94.31(2)°, V=381.5/377.5 Å³; M=Cd: a=7.356(2)/7.319(2), b=10.416(2)/10.423(3), c=5.407(1)/5.371(2) Å, β=93.85(1)/93.30(2)°, V=413.4/409.1 Å³. Layers of corner-shared MO₆ octahedra and phosphate tetrahedra are linked by three of the four crystallographically different hydrogen bonds. The fourth hydrogen bond (located within the layer) is worth mentioning because of the short O_h?O bond distance of 2.57-2.61 Å at room temperature (2.56-2.57 Å at 120 K); only for M=Mg it is increased to 2.65 Å. Any marked temperature-dependent variation of the unit-cell dimension is observed only vertical to the layers. The analysis of the infrared (IR) spectroscopy data evidences that the internal PO₄ vibrations are insensitive to the size and the electronic configuration of the M²⁺ ions. The slight strengthening of the intra-molecular P-O bonds in the Mg salt is caused by the more ionic character of the Mg-O bonds. All IR spectra exhibit the characteristic “ABC trio” for acidic salts: 2900-3180 cm⁻¹ (A band), 2000-2450 cm⁻¹ (B band) and 1550-1750 cm⁻¹ (C band). Both the frequency and the intensity of the A band provide an evidence that the PO₂(OH)₂ groups in M[PO₂(OH)₂]₂·2H₂O compounds form weaker hydrogen bonds as compared with other acidic salts with comparable O?O bond distances of about 2.60 Å. The observed shift of the O-H stretching vibrations of the water molecule in the order M=Mg>Mn≈Fe≈Co>Ni>Zn≈Cd has been discussed with respect to the influence of both the character and the strength of M↔H₂O interactions.     

Crystal structures of syndiotactic poly(p-methylstyrene) clathrates with two guest molecules having very similar shape and volume

In the present paper we report on the clathrate structures of syndiotactic poly(p-methylstyrene) (s-PPMS) containing chlorobenzene (cell constants: a = 23.5 Å, b = 12.0 Å, c = 7.9 Å and γ = 112.4°; space group: P2₁/a) and toluene (cell constants: a = 19.5 Å, b = 13.5 Å, c = 7.9 Å and γ = 90°; space group: P2₁). Despite the extreme similarity between the shape and volume of these two molecules, they give rise to completely different clathrate structures, the first belonging to α class, the second belonging to β class. Moreover the clathrate form containing chlorobenzene represent the first case in which a α class clathrate form of s-PPMS contains two guest molecules in each cavity while the crystal structure here proposed for the s-PPMS/toluene clathrate represents a new example of chiral crystalline phase in which the polymer helices assume all the same chirality in the lattice. These results underline the fact that the choice of a particular structural organization in the process of clathrates’ formation of s-PPMS is not easily referable only to steric effects but seems to be dependant even on the chemical structure of the guest molecules. A comparison with syndiotactic polystyrene is also done.     

Os(CO)2(η-SC5H4N(O))(η-SC5H4N): structural evidence for the transformation of pyridine-2-thione N-oxide to pyridine-2-thiolate in osmium complexes

The reaction of Os₃(CO)₁₂ with an excess of 1-hydroxypyridine-2-thione and Me₃NO gives three mononuclear osmium complexes Os(CO)₂(η²-SC₅H₄N(O))₂ (1), Os(CO)₂(η²-SC₅H₄N(O))(η²-SC₅H₄N) (2), and Os(CO)₂(η²-SC₅H₄N)₂ (3). The results of single-crystal X-ray analyses reveal that complex 1 contains two O,S-chelate pyridine-2-thione N-oxide (PyOS) ligands, whereas complex 2 contains one O,S-chelate PyOS and one N,S-chelate pyridine-2-thiolate group. The unique structure of 2 provides evidence of the pathway for this transformation. When this reaction was monitored by ¹H NMR spectroscopy the triosmium complexes Os₃(CO)₁₀(μ-H)(μ-η¹-S-C₅H₄N(O)) (4) and Os₃(CO)₉(μ-H)(μ-η¹:η²-SC₅H₄N(O)) (5) were identified as intermediates in the formation of the mononuclear final products 1-3. The proposed pathway is further supported by the observation of several dinuclear osmium intermediates by electrospray ionization mass spectrometry. In addition, the reaction of Os₃(CO)₁₂ with 1-hydroxypyridine-2-thione in the absence of Me₃NO at 90 °C generated mononuclear complex 2 as the major product along with smaller amounts of complexes 1 and 3. These results suggest that the N-oxide facilitates the decarbonylation reaction. Crystal data for 1: monoclinic, space group C2/c, a = 26.9990(5) Å, b = 7.6230(7) Å, c = 14.2980(13) Å, β = 101.620(2)°, V = 2882.4(4) ų, Z = 8. Crystal data for 2: monoclinic, space group C2/c, a = 5.7884(3) Å, b = 13.9667(7) Å, c = 17.2575(9) Å, β = 96.686(1)°, V = 1385.69(12) ų, Z = 4.     

Syntheses and crystal structures of binuclear ruthenium complexes bearing 1,8′-bis(diphenylphosphinomethyl)naphthalene

Treatment of [RuCl₂(η⁶-C₆H₆)]_x with bidentate phosphine ligand BDNA [1,8-bis(diphenylphosphinomethyl)naphthalene] in methanol at room temperature gave η⁶-benzene-ruthenium complexes Ru₂Cl₄(η⁶-C₆H₆)₂(μ-BDNA) (1). Complex 1 further reacted with AgBF₄ to form complex [Ru₂Cl₂(μ-Cl)(η⁶-C₆H₆)₂(μ-BDNA)](BF₄) (2). [RuCl₂(η⁶-C₆H₆)]_x reacted with BDNA in refluxing methanol and then the reaction solution was treated with AgBF₄ to generate complex [Ru₂Cl₂(η⁶-C₆H₆)₂(μ-BDNA)₂](BF₄)₂ (3). Their compositions and structures had been determined by elemental analyses, NMR spectra and single crystal X-ray diffractions. X-ray diffraction showed that complex 1 belonged to monoclinic crystal system, P2₁/c space group with Z = 4, a = 12.810 Å, b = 21.507 Å, c = 18.471 Å, β = 107.95°; complex 2 belonged monoclinic crystal system, P2₁/n space group with Z = 4, a = 14.498 Å, b = 15.644 Å, c = 20.788 Å, β = 103.404°, and complex 3 belonged to monoclinic crystal system, P2₁/n space group with Z = 2, a = 13.732 Å, b = 14.351 Å, c = 19.733 Å, β = 94.82°.     

Stereoselective synthesis of (E)-N,N-diethyl-3-(imidazo[1,2-a]pyrid-2-yl)-2-(phenylsulfonyl)propenamide

The title compound, gem-amidovinylsulfone 3, was synthesized stereoselectively by aldolic condensation of N,N-diethylphenylsulfonylacetamide 1 on imidazo[1,2-a]pyridine-2-carbaldehyde 2 adding Et₃N at the end. The X-ray crystal structure of 3 [C₂₀H₂₁N₃O₃S: M_r=383.5, monoclinic, P2₁, a=8.191(4) Å, b=21.132(2) Å, c=11.752(1) Å, β=96.40(2)°, V=2022(1) Å³, Z=4 (two molecules per asymmetric unit), D_calc=1.260 g cm⁻³, λ(Mo Kα)=0.71073 Å, μ=0.184 mm⁻¹, F(000)=808, T=293(2)K, R=0.059 for 5105 observed reflections with I≥2σ(I)] was determined, and confirmed the (E) configuration.     

The iron potassium diarsenate KFeAs2O7 structural, electric and magnetic behaviors

Crystals of a new potassium iron (III) diarsenate (KFeAs₂O₇) have been grown and characterized by single crystal X-ray diffraction. It crystallizes in the triclinic space group , with a=7.662(1) Å, b=8.402(2) Å, c=10.100(3) Å, α=90.42(3)°, β=89.74(2)°, γ=106.39(2)°, V=623.8(3) Å³ and Z=4. The final agreement factors are R=0.0342, wR=0.0889, S(F²)=1.01; the structural model is validated by bond valence sum (BVS) and charge distribution (CD) methods. The structure consists of corner-sharing FeO₆ octahedra and As₂O₇ diarsenate groups, the three-dimensional framework delimits tunnels running along [0 1 0] direction where the potassium ions reside. The crystal structure of the title compound is different from that of the monoclinic KAlP₂O₇ type but structural relationships exist between the frameworks. Impedance measurements (frequency/temperature ranges: 5-13,000 Hz/526-668 K) show KFeAs₂O₇ an ionic conductor being the conductivity 2.76×10⁻⁷ S cm⁻¹ at 568 K and E_a is 0.47 eV. The BVS model suggests that the most probable potassium conduction pathway is along b-direction. Magnetic measurements reveal the Curie—Weiss type paramagnetic behavior over the range 30-300 K and ferromagnetic below 29.3 K.