Centrosymmetric Monoclinic Space Research Articles

Synthesis and characterization of the new tin borate SnB8O11(OH)4

AbstractA new tin(II) borate with the composition SnB8O11(OH)4was synthesized by a simple hydrothermal process. It crystallizes in the centrosymmetric monoclinic space groupP21/n(no. 14) with the lattice parametersa=790.1(1),b=1402.2(2),c=994.8(1) pm, andβ=90.40(5)° (Z=4). The new compound SnB8O11(OH)4is isotypic to PbB8O11(OH)4and isostructural to BaB8O11(OH)4. The borate layers are built up from fundamental building blocks (FBBs) with the composition [B8O11(OH)4]2−. Four of these FBBs form a nine-membered ring wherein the Sn2+cations are located. These boron-oxygen layers are further connected by O–H···O hydrogen bond interactions. The characterization of SnB8O11(OH)4is based on single-crystal X-ray diffraction data, vibrational spectroscopy, DFT calculations, and thermoanalytical investigations including high temperature powder XRD.

Novel bis(azole) pincer palladium complexes: synthesis, structures and applications in Mizoroki–Heck reactions

Two novel NCN-pincer complex precursors bearing frameworks of 2,6-bis(oxazol-4-yl)benzene (A) and 2-(thiazol-4-yl)-6-(oxazol-4-yl)benzene (B) were synthesized. Palladations of A and B afforded two new bis(azole) pincer complexes, [(A-κ(3)NCN)PdBr] (1) and [(B-κ(3)NCN)PdBr] (2). Both complexes were fully characterized by NMR, MS, DSC-TGA and single-crystal X-ray diffraction analysis. Complex 1 crystallizes in a noncentrosymmetric orthorhombic space group Cmc2(1) (No. 36, Z=4). Complex 2 crystallizes in a centrosymmetric monoclinic space group P2(1)/n (No. 14, Z=4). Despite the similarity in their chemical formulas, the structures of the two complexes are subtly different: they are built up of two-dimensional supramolecular layers with identical topology, but stacked in different sequences, i.e., the layers in complex 1 are stacked in an AAAA-type fashion, while those in complex 2 are stacked in an alternating AA(-1)AA(-1) sequence (A denotes a layer; A(-1) stands for A's inversion symmetry equivalent). In addition, the complexes showed good catalytic activity toward Mizoroki-Heck reactions.

Synthesis, Characterisation and Molecular Hyperpolarisabilities of Pseudo‐Octahedral Hydrido(nitrile)iron(II) Complexes for Nonlinear Optics: X‐ray Structure of [Fe(H)(dppe)2(4‐NCC6H4NO2)][PF6]·CH2Cl2

AbstractA series of ionic pseudo‐octahedral trans‐hydrido(nitrile)iron(II) complexes with the general formula [Fe(H)(dppe)2(4‐NCR)][PF6] [dppe = 1,2‐bis(diphenylphosphanyl)ethane; R = acceptor‐substituted conjugated ligand] have been synthesised by chloride abstraction from the starting compound trans‐[FeHCl(dppe)2] and fully characterised. First hyperpolarisabilities (β) have been determined by hyper‐Rayleigh scattering (HRS) at the fundamental wavelength of 1072 nm and the high near‐resonant values obtained (up to 1130 × 10–30 esu) are interpreted in terms of the two‐level model (TLM) and are correlated with IR and NMR spectroscopic data. Wavelength‐dependent HRS has been performed in the 1072–1580 nm range for two of the compounds, namely [Fe(H)(dppe)2{4‐NC(CH)(CH)C6H4NO2}][PF6] and [Fe(H)(dppe)2{4‐NCC6H4(CH)(CH)C6H4NO2}][PF6]. These results clearly show the two‐photon resonance but also the shortcomings of the TLM when it comes to deriving reliable static β values. A structural study of the compound [Fe(H)(dppe)2(4‐NCC6H4NO2)][PF6] by X‐ray diffraction shows that it crystallises in the centrosymmetric monoclinic space groupP21/n, with four molecules in the unit cell and a pairwise antiparallel alignment of the dipoles. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

A structural model for a new class of conformationally constrained retinoid: (2Z,4E)-4-[3′,4′-dihydro-1′(2′H)-naphthalene-1′-ylidene]-2-butenoic acid

Racemic (2Z,4E)-4-[3′,4′-dihydro-1′(2′H)-naphthalene-1′-ylidene]-2-butenoic acid (1) is a polyene chain-shortened analog of (9Z)-retinoic acid (3) which uses a tetrahydronaphthyl ring to conformationally constrain the C6-C7 single bond (retinoic acid numbering). The structure of (1) was obtained to determine the effects of the tetrahydronaphthyl ring on the ring to polyene chain conformation as compared to a published crystal structure for (9Z)-retinal (2). The results reveal significant differences between the solid state structures of (1) and (2), particularly for torsion angles about C6, C7 and C8, C9. The title compound crystallizes in the centrosymmetric monoclinic space groupP21/n withZ=4. (Cell dimensions:a=10.863(2) A,b=7.637(2) A,c=15.781(3) and β=106.11(3)°.) The structure was refined toR=3.88% for those 1132 unique data with |F o|>6σ(F o). In the crystal structure, the molecules adopt a hydrogen bonded dimeric structure.

Crystal structure ofmer,trans-[Ru(NO2)(trpy) (PPh3) 2 + ][PF 6 − ]: a “problem structure”

The complexmer,trans-[Ru(NO2)(trpy)(PPh3) 2 + ][PF 6 − ] crystallizes in the centrosymmetric monoclinic space groupP21/n withZ=4; the ruthenium atom lies close toy=1/4 and all data withh+l=2n+1 are systematically weak. The trpy ligand is not strictly planar, but has a “dish-like” geometry. The nitro ligand is rotated from the plane of the Ru(trpy) moiety, the N3Ru/NO2 interplanar angle being 32.5o. Ruthenium-ligand distances are: Ru−PPh3=2.418(4) A and 2.429(4) A, Ru−NO2=2.063(12) A, Ru−N(trpy, outer)=2.100(12) A and 2.116(12) A and Ru−N(trpy, central)=2.004(11) A.