The X-ray crystal and molecular structure of 5′-bromo-5′-deoxythymidine

5′-Bromo-5′-deoxythymidine (1) crystallizes with four molecules in a monoclinic unit cell of space group C2. The ribose ring adopts an envelope conformation, transient between T and E₀ (O4′-exo), with the C1′ atom being in the flap position. In the crystal lattice, the molecules are connected by intermolecular one-dimensional chains of hydrogen bondings from the hydroxyl hydrogen H3′(O3′) to the carbonyl oxygen O4. The differences in conformation and a hydrogen-bonding system of 1 with comparison to the structure of thymidine are observed. © 1998 John Wiley & Sons, Inc. Heteroatom Chem 9: 591–596, 1998     

The crystal and molecular structure of η5-cyclopentadienyliodomethyl(methylthio)carbene-(triphenylphosphine)iridium(III) iodide

The crystal and molecular structure of η⁵-cyclopentadienyliodomethyl(methylthio)carbene(triphenylphosphine)iridium(III) iodide [IrI{C(Me)SMe}(η⁵-C₅H₅)(PPh₃)]I has been determined from three dimensional X-ray data in order to clarify the contribution of the α-sulphur atom to the bonding in this carbenoid complex.The compound crystallizes in space group Pbc2₁ with four formula units in a cell of dimensions a 9.745(6), b 15.201(8), and c 17.364(10) Å. Least-squares refinement of the structure has led to the final discrepancy index R = 0.047 for the 1655 symmetry-independent observable reflections. The coordination geometry about the iridium atom is approximately tetrahedral; the coordination positions are occupied by the η⁵-C₅H₅ ring center, the phosphorus, the iodide I(1) and the carbon C(6) of the C(Me)SMe ligand (IrRc 1.89, IrP 2.280(7), Ir(1) 2.651(2) and IrC(6) 2.03(3) Å).The bonding of the C(Me)SMe group indicates that this complex must be formulated as a C(Me)SMe complex of iridium(III).     

四氢噻唑-2-硫酮的晶体结构及分子结构

四氢噻唑-2-硫酮晶体属单斜晶系,空间群P2_1/n;晶胞参数a=13.844(7)A,b=5.614(2)A,c=13.516(7)A,β=95.08(5)°;V=1046.3(9)A~3;Z=8。衍射强度数据系在Syntex R3四圆衍射仪上收集。结构的初始模型用直接法解得,经块矩阵最小二乘精修后,R值为0.082。结构分析表明分子结构介于1和2之间,分子中S(1)、S(2)、N、C(1)等原子共面,具有共轭效应。用自编CNDO/2程序计算了四氢噻唑硫酮及N-苯甲酰基四氢噻唑硫酮的原子荷电密度、偶极矩及总能量.解释了苯甲酰基四氢噻唑硫酮的生色效应及胺解性能。     

The crystal and molecular structure of (-)-phaseollin

X-ray analysis has defined the molecular structure of (-)-phaseollin C₂₀H₁₈O₄ a pterocarpan with lipophilic antifungal activity, isolated from Phaseolus vulgaris L. The orthohombic crystals belong to the space group P2₁2₁2₁ with a =6.540(3), b = 12.975(6), c = 19.388(4) Å and Z =4. The structure was solved by direct methods from diffractometer data measured with CuKα radiation, and refined to a final R index of 0.083 for the 992 observed terms. The molecular skeleton(I) has a cis B/C ring junction. Viewed down C(6B)-C(7) the conformation is staggered; ring C is envelope whereas ring B is skewed with C(6B) and C(7) lying respectively above and below the plane of the other ring atoms.     

The crystal molecular structure of cis-13,13-dimethyl-13-azoniabicyclo [10.1.0] tridecane iodide

The crystal and molecular structure of cis-13,13-dimethyl-13-azoniabicyclo[10.1.0]tridecane iodide has been determined by a three-dimensional, single-crystal, x-ray diffraction study. The compound crystallizes in the orthorhombic space group Pnam with cell dimensions a_Q = 21.36 ± .01, b_O = 9.07, c_O = 8.29 Å. The aziridine ring is fused to the cyclododecane ring with fusion angles of 123.5°. The molecule is bisected by a mirror plane with the cyclododecane portion distorted from its anticipated square conformation. Transannular hydrogen interactions are estimated on the basis of geometric considerations. A final value of R = 0.112 was obtained for the 557 non-equivalent reflections which were observed.     

Synthesis and crystal structure of CuZrTiO5—A new crystal structure type

A new compound, CuZrTiO₅, was synthesized as strongly pleochroic green crystals from the oxides between 995 and 1010 °C, 1 atm. Its crystal structure was determined by single crystal XRD, resulting in R (F²>2σ(F²))=0.032 and wR (all data)=0.079). CuZrTiO₅ is orthorhombic, space group P2₁2₁2₁, a=3.5871(3) Å, b=6.6968(4) Å, c=14.6679(9) Å, V=352.35(4) Å³, Z=4. The structure is topologically similar to In₂TiO₅ but differs in space group and cation coordination. CuZrTiO₅ has relatively regular TiO₆ polyhedra, but coordination is 7+1 for Zr, and 4+2 for Cu due to the Jahn-Teller effect. Ordering of the long Cu-O bonds causes reduction in symmetry relative to In₂TiO₅. Layers of Cu alternate with Ti+Zr on (001), giving rise to a distinct cleavage. Bond valence sums on Ti and Zr are far from ideal, which appears due to the limited ability of this structural topology to avoid close next-nearest neighbour distances.     

The crystal and molecular structure of 3,4-quinoxalino-1-telluracyclopentane C10H8N2TeII

The crystal and molecular structure of 3,4-quinoxalino-1-tellura(II)cyclopentane has been determined by X-ray diffraction at room temperature. The crystals are tetragonal, space group I4₁/a with a = b = 25.315(8), c = 6.010(1) Å and V = 3851.38 ų. The density of 1.96 g cm^?3 calculated on the basis of 16 molecules per unit cell is in agreement with the flotation value of 1.91 g cm^?3. The structure has been refined to a conventional R value of 0.0408 using 744 independent observed reflections obtained from four-circle diffractometer measurements. The structure consists of discrete molecules TeC = 2.134 Å (av.), CN = 1.343 Å (av.) and angle CTeC = 80.7° (e.s.d. 0.5) but the intermolecular TeTe bonds (3.791 and 3.998 Å) are less than the sum of the Van der Waals' radii thus indicating the presence of secondary bonding. These short intermolecular contacts in the crystal structure are consistent with the anomalous physical properties observed.     

Phenylbis(2- pyridyl)phosphine: P- vs. N,N′-coordination in carbonylmolybdenum-(O) and -(II) complexes

The first carbonyl molybdenum-(O) and -(II) complexes with phenylbis(2-pyridyl)phosphine (PPhpy₂) have been synthesized. PPhpy₂ reacts with [Mo(CO)₅(NCMe)] to give [Mo(CO)₅(PPhpy₂-P)]. With [Mo(CO)₄(NBD)] (NBD = norbornadiene) it gives [Mo(CO)₄(PPhpy₂-P)₂] when a 2 : 1 ratio is used, or [MO(CO)₄(py₂PhP---N,N′)] for a 1 : 1 ratio. Decarbonylation of any of these pyridylphosphine complexes leads to an oligomer of formula {MO(CO)₃(μ-PPhpy₂)}_n, which is also obtained after heating [MO(CO)₆] in solution with an equimolar amount of PPhpy₂. The oligomer undergoes oxidative addition by iodine or allylbromide to give [MoI₂(CO)₃(py₂PhP---N,N′)], or [MoBr(η³-CH₂CHCH₂)(CO)₂(py₂PhP---N,N′)], respectively. These complexes are also obtained by addition of equimolar amounts of PPhpy₂ to solutions of [MoI₂(CO)₃(NCMe)₂] and MoBr(η³-CH₂CH CH₂)(CO)₂(NCMe)₂, respectively. The ligand tends to act as a P-donor towards molybdenum(O) substrates, and as a chelating N,N′-donor in molybdenum (II) complexes.     

Crystal and molecular structure of the alkaloid dictysine

In order to determine the spatial structure of the diterpene alkaloid dictysine unambiguously, x-ray structural analysis has been performed: diffractometer, CuK radiation, 1028 reflections, direct method, R factor 0.118. It has been established that dictysine has not a songorine but a denudatine skeleton. All the hydroxy groups participate in inter- and intramolecular hydrogen bonds.Institute of Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 230–235, March–April, 1982.     

Crystal and molecular structure of the alkaloid dictysine

In order to determine the spatial structure of the diterpene alkaloid dictysine unambiguously, x-ray structural analysis has been performed: diffractometer, CuK_α radiation, 1028 reflections, direct method, R factor 0.118. It has been established that dictysine has not a songorine but a denudatine skeleton. All the hydroxy groups participate in inter- and intramolecular hydrogen bonds.