Volume 225, Issue 6 -

The NbCl 5 adducts of M[NbCl 6 ] · NbCl 5 with M = K or NO are structurally related via their common super group Fmmm . K[NbCl 6 ] · NbCl 5 crys tallizes in the triclinic space group C -1 with a = 9.898(1), b = 9.443(1), c = 17.370(1) Å, α = 89.57(1), β = 108.49(1), γ = 90.54(1)° and Z = 4 at room temperature. For the mono clinic nitrosonium compound with space group C 2/ c X-ray diffraction data have been recorded at 173 K giving a = 9.530(1), b = 9.412(1), c = 33.38(1) Å, β = 92.68(1)° and Z = 8. Layers of NbCl 5 dimers alternate with cation-centred double layers of the NbCl 6 – ions, oriented parallel to the a – b plane. Com pared to the cubic perovskite SrTiO 3 , the NbCl 6 – ‘octahedra’ of the K + salt are uniformly rotated by 5° around the stack ing axis. On the contrary, the NO + salt shows ‘antiferrorotative’ ordering by ±12° in alternate layers. Crystal symmetry and twinning laws reflect the structural differences, but the similarity between both structures prevails.

The crystal structure of CaH 2 has been studied from neutron powder diffraction (NPD) at 295 K in a non-deuterated sample; a good quality NPD pattern was obtained in spite of the hydrogen incoherent scattering. The structure was refined by the Rietveld method in the Pnma space group (No. 62), Z = 4, with unit-cell parameters a = 5.9600(1), b = 3.6006(7) and c = 6.8167(1) Å. The two kinds of crystallographically independent H atoms, H1 and H2, are located in tetrahedral and square-pyramidal cavities, respectively, while Ca ions are nine-fold coordinated to hydrogen atoms. The average 〈Ca—H1〉 and 〈Ca—H2〉 bond lengths are 2.279 and 2.544 Å, respectively. Bond valence calculations show that Ca—H1 bonds are under compressive stress, whereas Ca—H2 bonds undergo tensile stress in a structure with a relatively high global instability index. It is also remarkable that the displacement factors for H2 are significantly larger than for H1, suggesting an increased lability for the Ca—H2 bonds. We provide with an analysis of the isotope effect, by comparing the present results on CaH 2 with literature data on CaD 2 ; we indeed observe a higher distortion of the H1 and H2 coordination polyhedra with respect to the deuteride, as observed in other isostructural dihydrides.

Three uranyl sulfates, (C 6 H 20 N 4 )[(UO 2 ) 2 (SO 4 ) 4 · (H 2 O) 2 ](H 2 O) 6 (TETAUS), (C 15 H 14 N 3 )[(UO 2 )(SO 4 ) 2 ](NO 3 ) · (H 2 O) 2 (TPUS), and K 2 [(UO 2 )(SO 4 ) 2 (H 2 O)] · H 2 O (KUS), and two uranyl selenates, K(H 3 O)[(UO 2 ) 2 (SeO 4 ) 3 · (H 2 O)](H 2 O) 6 (KUSe) and (H 3 O) 2 [(UO 2 ) 2 (SeO 4 ) 3 · (H 2 O)] (USe), were synthesized by slow evaporation of aqueous solutions at room temperature. TETAUS crystallizes in space group P -1, a = 6.7186(5) Å, b = 9.2625(7) Å, c = 13.1078(9) Å, α = 72.337(2)°, β = 89.198(2)°, γ = 70.037(1)°, V = 726.89(9) Å 3 , Z = 1. TPUS is triclinic, P -1, a = 6.9732(7) Å, b = 13.569(1) Å, c = 13.641(1) Å, α = 111.809(2)°, β = 102.386(2)°, γ = 93.833(2)°, V = 1150.0(2) Å 3 , Z = 2. KUS is orthorhombic, Cmca , a = 12.171(2) Å, b = 16.689(3) Å, c = 10.997(2) Å, V = 2233.8(6) Å 3 , Z = 8. These uranyl sulfates are built from infinite one-dimensional uranyl sulfate chains with different topologies. KUSe is monoclinic, P 2 1 /n, a = 14.715(1) Å, b = 10.1557(7) Å, c = 15.833(1) Å, β = 114.415(1)°, V = 2154.5(3) Å 3 , Z = 4. Its structure is based on a two-dimensional uranyl selenate sheet. USe crystallizes in space group P 2 1 /c, a = 10.6124(2) Å, b = 14.7717(3) Å, c = 13.7139(3) Å, β = 96.989(1)°, V = 2133.86(8) Å 3 , Z = 4, with a complex three-dimensional uranyl selenate framework containing channels extending in three directions.

The synthesis and characterization of gauche-N,N ′-bis-[(2-cyanoethyl)-(2-hydroxyphenylmethyl)]ethane diamine, BNSalanH 2 and anti-N,N ′-bis-[(methylpropanoate)-(2-hydroxyphenylmethyl)]ethane diamine, BPSalanH 2 are reported. These BNSalanH 2 , O 2 N 4 , and BPSalanH 2 , O 4 N 2 , molecules have both acidic and basic groups. The BNSalanH 2 and BPSalanH 2 molecules adopt a gauche and anti conformation, respectively, and Z stereochemistries. The conformations are governed by intramolecular interactions of both classical and non classical hydrogen bond types. In addition, a 3D self-arrangement in BNSalanH 2 is created by C-HN nitrile hydrogen bonds linking molecules along [100] and [010]. The X-ray data for BNSalanH 2 are: tetragonal , P 41212, a = 7.7030(11) Å, b = 7.7030(11) Å, c = 34.907(7) Å, V = 2071.2(6) Å 3 , Z = 4, R 1 = 0.0483; for BPSalanH 2 are: monoclinic , P 21/ c , a = 12.2572(5) Å, b = 7.9993(4), c = 13.4437(5) Å, β = 108.202(2)° V = 1252.18(9) Å3, Z = 2, R 1 = 0.0614.

The molecules of the (pyrazinecarbonyl)hydrazones of the heterocyclic aldehydes RCHO with R = pyrrol-2-yl, furan-2-yl, thien-2-yl and pyridin-2-yl corresponding to compounds ( 2: X = NH), ( 2: X = O), ( 2: X = S) and 3 , respectively, are formally rather similar. Despite this the molecular packing and intermolecular interactions show unexpectedly wide variation throughout the series. In 2 hydrogen-bonds link the planar molecules edge to edge to form chains or, in one case, planar ribbons while 3 exhibits zig-zag chain connectivity. Three-dimensional connectivity is attained by intermolecular hydrogen-bonds alone in ortho -( 2: X = S), the orthorhombic polymorph of ( 2: X = S) and by intermolecular hydrogen-bonds combined with π···π interactions in ( 2: X = O) and 3 . No more than two-dimensional layer connectivity is found in ( 2: X = NH) and the monoclinic polymorph, mono -( 2: X = S) of ( 2: X = S).

The new transition metal benzenesulfonate (bs) complexes of 2,2″-bipyridyl (bpy) have been synthesized and characterized by elemental analyses, magnetic moments, UV-Vis, IR, thermal analysis techniques. The bs anion does not coordinate to the metal ions and is present as the counter-ion in the Co(II) ( 2 ), Ni(II) ( 3 ) and Cu(II) ( 4 ) complexes, but coordinates to the Mn(II) ion as a monodentate ligand. The Mn(II) complex ( 1 ) crystallizes in the orthorhombic crystal system with Pbca space group. The complex ( 1 ) is the first crystallographically characterized Mn(II) benzenesulfanato complex in which the bs anion is coordinated to metal ion. The manganese centre has a significantly distorted octahedral coordination by two bpy and bs ligands. bs molecules are joined by O7—H7A...O2 and O7—H7B...O3 hydrogen bonds, forming a centrosymmetric dimers which are linked by π–π interactions. All complexes exhibit similar decomposition characteristics. Magnetic susceptibility measurement shows that complex 2 has orbital interaction.