Pierre Palvadeau

The tailoring of crystal structures via the self-assembly of organic coordination compounds by N⋯I non-covalent halogen bonds: co-crystals of sterically hindered N-heterocycles and 1,4-diiodo-tetrafluorobenzene

The N-containing heteroaromatics 2,3,5,6-tetramethylpyrazine (tmpyr), 2,2′-bipyridine (2,2′-bpy), 2,4′-bipyridine (2,4′-bpy) and o-phenanthroline (phen) were each cocrystallized with 1,4-diiodo-tetrafluoro-benzene (TFDIB). The effect of the sterically constrained aza cycles on supramolecular assembly and the crystal structure determining interactions is discussed. The N⋯I non-covalent halogen bonds are the main directing interactions responsible for the observed structures. Nevertheless, steric hindrance of the donor sites increases the impact of weaker intermolecular interactions such as CH⋯F bonding and π–π interactions provoking changes in the coordination behaviour of the donor modules. In spite of steric constraints, the co-crystals tmpyr·TFDIB (1) and 2,2′-bpy·TFDIB (2) exhibit polymeric structures consisting of infinite one-dimensional chains of alternating electron donors (D) and acceptors (A). In contrast, the structures of the cocrystals 2,4′-bpy·TFDIB (3) and phen·TFDIB (4) reveal a packing of termolecular [A1D2] complexes. It follows that the structure type of such halogen bonded supramolecular assemblies can be tuned by choosing the appropriate precursors.

Investigation of an intercalation compound of ferrocene in FeOCl Part I: X-ray and mössbauer resonance studies

Abstract Intercalation of ferrocene in lamellar iron oxide chloride has been obtained by reaction between FeOCl and ferrocene either dissolved in benzene or in vapour phase. X-ray single crystal studies have confirmed the expansion of the Van der Waals gap and the shift of the FeOCl layers previously deduced from powder data (1). Mossbauer resonance studies have shown below about 100 K the ionization of ferrocene molecules into ferricinium cations and the correlative formation of an equal number of ferrous ions in the host lattice. For Fe 3+ and Fe 2+ , two types of sites are observed: those with only Fe 3+ as nearest ion neighbors, and those with at least one Fe 2+ as nearest cation neighbor. From a plot of the hyperfine field vs. T, the Neel temperature has been estimated to be ⋍ 75 K , relaxation effects preventing a more precise determination. Above 245 K, electron hopping between Fe 2+ and Fe 3+ occurs, and ferricinium ions are no longer observed. Between 100 and 245 K, the Mossbauer spectra reflect intermediate situations between those corresponding to electronic delocalization at higher temperatures and those characterizing localized electrons at lower temperatures.

Lead-antimony sulfosalts from Tuscany (Italy). IV. Crystal structure of pillaite, Pb9Sb10S23CIO0.5, an expanded monoclinic derivative of hexagonal Bi(Bi2S3)9I3, from the zinkenite group

The crystal structure of pillaite, a recently described Pb-Sb oxy-chloro-sulfosalt from the Buca della Vena mine, Tuscany (Italy), was solved and refined to a residual R of 0.045 in the monoclinic system, with space group C2/m, and a = 49.49(1), b = 4.1259(8), c = 21.828(4) A, β = 99.62(3) 0 , V = 4394(2) A3. The structural formula is Pb 9.16 Sb 9.84 S 23 ClO 0.5 , corresponding to the electron-microprobe one Cu 0.10 Pb 9.16 Sb 9.84 S 22.94 Cl 1.06 O 0.5 (ideally Pb 9 Sb 10 S 23 ClO 0.5 ), with Z = 4 and D cale. = 5.87. The crystal structure is organized around pseudo-threefold axes where chlorine atoms are in a trigonal prismatic coordination with Pb atoms. An oxygen position, half-filled, is bonded to two Sb atoms, like in scainiite. Pairs of pseudo-trigonal rods parallel to the elongation b-direction are connected along [102] to form rod-layers. The pillaite structure is an expanded homologue of hexagonal Bi(Bi 2 S 3 ) 9 I 3 . Among lead sulfosalts, it belongs to the zinkenite group of cyclically twinned structures. Pillaite is the first example of a Pb-Sb sulfosalt where small amounts of two anion species simultaneously play a specific crystal chemical role, which is essential for the stabilization of the crystal structure: chlorine, like in dadsonite, and oxygen, like in scainiite.

Lead-antimony sulfosalts from Tuscany (Italy): II - Crystal structure of scainiite, Pb14Sb30S54O5, an expanded monoclinic derivative of Ba12Bi24S48 hexagonal sub-type (zinkenite group)

The crystal structure of scainiite, Pb 14 Sb 30 S 54 O 5 , has been solved from single-crystal X-ray data and refined to an R index of 8.9 % based on 3703 unique reflections. The structure is monoclinic C 2/ m , with cell parameters a 51.996(8), b 8.148(1), c 24.311(4) A, β 104.09(1)°, V 9990(10) A 3 , and with Z = 4. The structure analysis was essential in determining the position of oxygen atoms in a special double-ribbon, Sb 8 (Pb,Sb) 2 S 10 O 5 , directly related to the structure of kermesite, Sb 2 S 2 O. The general organization of the structure can be described according to the general principles developed by Makovicky (1993) for complex sulfides related to the PbS and SnS archetypes. This structure falls into the group of “pure rod structures” (zinkenite group), and is an expanded homologue of cyclic hexagonal Ba 12 Bi 24 S 48 . The expansion of the parent structure is obtained by shearing along a zig-zag surface, that creates lozenge shaped spaces in place of the original hexagonal channels, and filling these spaces by the kermesite-type fragments.

Lead-antimony sulfosalts from Tuscany (Italy). III. Pillaite, Pb9Sb10S23ClO0.5, a new Pb-Sb oxy-chloro-sulfosalt, from Buca della Vena mine

The new mineral pillaite, Pb9Sb10S23ClO0.5, an oxy-chloro-sulfosalt, has been found at Buca della Vena mine in the Apuan Alps, northern Tuscany, Italy. It crystallized in small fractures of dolomitic lenses in massive Fe- Ba ore, together with many Pb-Sb sulfosalts, among which the oxy-sulfosalt scainiite. Pillaite occurs as black acicu- lar crystals with metallic lustre, elongated // (010), up to 1 cm long and less than 0.1 mm thick. The mineral is brittle, opaque; VHN50 = 175 kg/mm2, dcalc = 5.77 g/cm3. In reflected light it shows a weak anisotropy and bireflectance, and

A new family of 2D antiferromagnets: the layered phosphonates MII (RPO3) · H2O; M Mn, Fe, Co, Ni; R = alkyl, phenyl

Abstract Magnetic susceptibility data are reported for the divalent metal phosphonates II (RPO 3 ) · H 2 O (M  Mn, Fe, Co, Ni; R = alkyl, phenyl). The quasi 2D square lattice formed by the M II ions within these compounds leads to 2D antiferromagnetic properties.

Lead-antimony sulfosalts from Tuscany (Italy). V. Definition and crystal structure of moëloite, Pb6Sb6S14(S3), a new mineral from the Ceragiola marble quarry

Moeloite is a new lead-antimony sulfosalt, Pb 6 Sb 6 S 14 (S 3 ), discovered in the Ceragiola marble quarry, near Seravezza town (Tuscany, Italy). Associated minerals are: sulphur, pyrite and enargite. It crystallizes as very thin needles and soft plumose aggregates of flexible thin fibres with a metallic lustre. Under the microscope it looks white, with moderate anisotropism, without polarization colours; reflectance values (air/oil): 40.0–37.8/26.6–24.2 (470 nm), 38.8–36.5/24.9–22.8 (546 nm), 38.6–36.7/23.4–21.4 (589 nm), 36.5–34.7/21.2–20.1 (650 nm). Moeloite is orthorhombic, space group P 2 1 22 1 , with unit cell parameters a 15.328(3), b 4.0400(8), c 23.054(5) A; V 1427.6(5) A 3 , with Z = 2; D calc. 5.86 g/cm 3 . Main X-ray powder diffraction lines [d(A), I, hkl ]: 3.724 (55)(106, 112), 3.427 (100) (403), 3.047 (85) (312, 214), 2.844 (58) (503), 2.779 (70) (016, 314), 2.753 (45) (116), 2.017 (80) (614, 020), 1.733 (50) (0112, 618, 2013). The crystal structure reveals Pb 6 Sb 6 S 16 rods parallel to b , and connected along c by a (S 3 ) 2- trimer due to an additional S atom, to form (100) rod-layers. The crystal structural formula is Pb 2+ 6 Sb 3+ 6 S 2- 14 (S 3 ) 2- . The formation of moeloite is subordinated to a high sulfur fugacity, which explains the S excess of its formula. The name is in honour of Dr. Y. Moelo (Nantes, France), who first synthesized this compound.

Preparation and characterization of a new iron (III) methylphosphonate

Abstract A new Iron(III) methylphosphonate HFe(CH 3 PO 3 ) 2 was obtained by refluxing a mixture of FeOCl and CH 3 PO 3 H 2 in a molar ratio of 1:2.5 in acetone. This reaction comes within the framework of our researchs in the field of lamellar materials bearing grafted acid groups, enabling possible applications as acid catalysts in heterogeneous liquid-solid organic reactions. On the basis of the physical data, the structural aspect of our material was discussed.

Microbiological reductions of chromen-4-one derivatives

Abstract From the microbiological reductions of 2-acetyl or 2-benzoylchromen-4-one both enantiomers of the corresponding alcohols were obtained with high enantiomeric excess. The absolute configurations were determined directly by an X-ray structural determination. The results obtained showed that for most of the microorganisms tested, an inversion of the configuration of the alcohol occurred with the change of the substituent (methyl to phenyl group) in position 2, but also with the presence of a bromine atom in position 6 of the aromatic ring, positioned quite far from the prochiral centre.

Lead-antimony sulfosalts from Tuscany (Italy). VI. Pellouxite, ∼ (Cu,Ag)2Pb21Sb23S55ClO, a new oxy-chloro-sulfosalt from Buca della Vena mine, Apuan Alps

Pellouxite, the second natural oxy-chloro-sulfosalt after pillaite, has been discovered in cavities of calcite veins in the small Fe-Ba deposit of Buca della Vena mine, Apuan Alps (Tuscany, Italy). The new mineral name honours professor Alberto Pelloux (1868–1948), curator of the mineralogical Museum at the University of Genova. Pellouxite occurs as black acicular flattened crystals with metallic lustre, up to 1 mm long and less than 0.05 mm thick. Main reflectance values [λ (nm), R air / R oil %]: 470, 38.3/23.8; 546, 37.3/22.4; 589, 36.9/21.5; 650, 35.2/19.6. It has monoclinic symmetry, space group C 2/ m , with a = 55.824(11), b = 4.0892(8), c = 24.128(5) A, β = 113.14(3)° and V = 5065(2) A 3 . The eight strongest lines of the X-ray powder diffraction pattern are [d(A), I obs (hkl)]: 4.002, 38 (606, 406); 3.878, 24 (206, 112); 3.562, 31 (804, 1202); 3.423, 100 (807, 1604, 407); 3.009, 25 (808, 912, 713); 2.948, 27 (1313, 1111); 2.265, 19 (409); 2.048, 20 (020). Electron probe microanalysis gives (mean of 15 spots; wt.%, error σ): Pb 47.17(20), Sb 31.16(23), Cu 0.89(5), Ag 0.59(5), S 19.08(6), Cl 0.33(3), O 0.39(15), Total 99.60. The unit formula, on the basis of Pb + Sb = 22 at. according to the crystal structure study, is (Cu 0.64 Ag 0.25 )Pb 10.36 Sb 11.64 S 27.07 Cl 0.42 O 1.11 ( Z = 4). Taking into account a 2 b superstructure, the crystal chemical formula is (Cu,Ag) 2-x Pb 21-x Sb 23+x S 55 ClO (x = 0.12; d calc. = 5.97 g/cm 3 ), derived from the stoichiometric one (Cu,Ag) 2 Pb 21 Sb 23 S 55 ClO. Pellouxite, structurally related to scainiite, is an expanded monoclinic derivative of synthetic hexagonal Ba 12 Bi 24 S 48 . It belongs to the zinkenite group of lead sulfosalts with cyclically twinned structures and their derivatives. Like for pillaite, its formation is the result of a complex sulfide deposition from hydrothermal brines, at relatively high temperature, and fO 2 /fS 2 conditions controlled by the pyrite-hematite-magnetite buffer.