摘要:

Sodium dihydrogen phosphate (NaH2PO4) is monoclinic, space group P21/c, witha= 6.808 (2),b= 13.491 (3),c= 7.331 (2) Å, β = 92.88 (3)°;Z= 8. The structure was solved and refined anisotropically (R= 0.028) with 1404 reflexions measured on a diffractometer (CuKα radiation). Corrections for absorption, secondary extinction and anomalous scattering were applied. The four independent hydrogen atoms were located on a difference map; they are involved in four O … O hydrogen bonds of length 2.654 (2), 2.589 (2), 2.559 (2), and 2.500 (2) Å. The short contact (2.500 Å), which is not astride any symmetry element, is of the type O‐H … O (asymmetrical). The distorted coordination polyhedra of the sodium atoms are discussed in the light of recent theories on electrostatic balance. Double layers of sodium polyhedra sharing edges, parallel to (010), can be observed in th

ISSN:0567-7408    

DOI:10.1111/j.1600-5740.1974.tb00001.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Potassium triselenylimide, K3(NSeO2)3, crystallizes in the monoclinic system, space group P21/c, with cell dimensionsa= 7.452 (8),b= 12.767 (11),c= 11.845 (10) Å, β = 113.95 (2)°,Z= 4. The structure was solved by a combination of direct methods and a difference Fourier synthesis from 1711hklreflexions collected on a Picker FACS‐1 diffractometer, with CuKα radiation. Full‐matrix least‐squares refinement (including anisotropic temperature factors) of the structure onFcarried out on 1472 reflexions greater than 3σF2, which were corrected for absorption, gave a residual of 0.055. Theanion in the structure has pseudosymmetry C3v(chair configuration) with mean Se‐N bond length of 1.768 (11) Å and Se‐O bond lengths in the range of 1.602 to 1.630 Å. All potassium atoms in the structure are octahedrally coordinated with resulting K‐O distances

ISSN:0567-7408    

DOI:10.1111/j.1600-5740.1974.tb00002.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

The crystal structure of modification III of 5‐ethyl‐5‐phenylbarbituric acid has been determined and refined to a conventionalRof 0.066 on 2296 reflexions. Form III is monoclinic,P21/c; a= 9.534,b= 11.855,c= 10.794 Å, β = 111.56°;Z= 4. Intensity data were collected on a four‐circle diffractometer using MoKα radiation. The structure was solved by direct methods, the hydrogen atoms located, and the positions of all atoms except hydrogens were refined independently with anisotropic temperature factors. Molecules in the structure are linked together by pairs of hydrogen bonds into infinite chains lying along 21axes. The conformation of the ethyl and phenyl groups is largely controlled by packing r

ISSN:0567-7408    

DOI:10.1111/j.1600-5740.1974.tb00003.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

The crystals of the title compound (C19H15Cl2CuN5O) are orthorhombic, space groupPbca; the unit cell dimensions area= 14.802 (3),b= 16.447 (4),c= 15.654 (4) Å;Z= 8. The structure has been determined from diffractometer data by Patterson and Fourier methods and refined by block‐diagonal least‐squares calculations toR= 4.3% for 2648 independent reflexions. The copper atom is five‐coordinated through two chlorine atoms (Cu‐Cl = 2.258, 2.500 Å) and three nitrogen atoms (Cu‐N = 2.039, 2.053, 2.058 Å) from the organic molecule which behaves as a tridentate ligand. The heteroatomic ring of the quinazoline system shows a half‐chair conformation, as a consequence of the imperfect hybridization of N(3) and N(4) and of the tetrahedral char

ISSN:0567-7408    

DOI:10.1111/j.1600-5740.1974.tb00004.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

The structure of the complex MgCr2O7.2[(CH2)6N4].6H2O has been determined by X‐ray diffraction to study the hydrogen bonds and the role of water in the crystal stabilization. The crystals are triclinic, space groupPĪ, witha= 10.02 (5),b= 13.68 (8),c= 9.81 (5) Å, α = 961 (5), β = 87.9 (5), γ = 101.0 (8)°,Z= 2 (MoKα radiation up to (sin θ)/λ = 0.691 Å−1with Weissenberg photographs). The crystal structure has been determined by the heavy‐atom method and refined by full‐matrix least‐squares calculations. The finalRis 0.067 (0.088 with non‐observed reflexions). The structure is characterized by two nearly tetrahedral CrO4groups joined through a shared oxygen atom, an octahedron [Mg(H2O)6]2+and two hexamethylenetetramine molecules, lin

ISSN:0567-7408    

DOI:10.1111/j.1600-5740.1974.tb00005.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

The discovery of two isomerstrans(m.p. 332°) andsyn(m.p. 255°) of the title compound and the assignment of conformations to them is due to Schönberg, Sodtke&Praefcke [Chem. Ber.(1969), 102, 1453]. X‐ray structure analysis confirms the assignment. Thesynisomer, which is converted quantitatively totranswhen molten, crystallizes inP21/cwithZ= 8 and thus has two asymmetric molecules per general position. Thetransisomer also crystallizes inP21/cbut withZ= 2 so that the molecule is centrosymmetric. Molecules of both isomers are severely overcrowded and their geometry is discussed. Thetransisomer has probably the lower free energy at all temperat

ISSN:0567-7408    

DOI:10.1111/j.1600-5740.1974.tb00006.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Nickel orthoborate, Ni3(BO3)2, crystallizes in the orthorhombic system, space groupPnnm, with two formula units in a cell of dimensionsa= 5.396 ± 0.001,b= 4.459 ± 0.001 andc= 8.297 ± 0.002 Å. The structure of Ni3(BO3)2has been determined by three‐dimensional Patterson synthesis. The positional and isotropic thermal parameters were refined by least‐squares analysis, yielding a finalRvalue of 0.086. All boron atoms are triangularly coordinated. There are two types of Ni atoms, both octahedrally coordinated and linked together by oxygen sharing to form a three‐dimensional network. Each oxygen atom is surrounded by three nickel atoms and one boron atom arranged in an irregular te

ISSN:0567-7408    

DOI:10.1111/j.1600-5740.1974.tb00007.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Evaporation of an aqueous solution of cytosamine triacetate, C24H36N4O9, yielded prismatic crystals of the orthorhombic space groupP212121, witha= 8.738,b= 12.654 andc= 25.596 Å. The crystal structure was determined by three‐dimensional X‐ray diffraction methods from 2411 independent reflexions measured on an automatic diffractometer. Using the symbolic addition method, the structure was solved from a series ofEmaps and Fourier syntheses, and refined by least‐squares calculations to a finalRvalue of 6.3%. The distances and angles of the cytosine moiety of the molecule do not compare well with those found in cytosine monohydrate and cytidine. The discrepancies are attributed to the influence of hydrogen bonding on the double bond character of the carbonyl bond C*(2)‐O*(2) and on the influence of theN4‐acetylation on the ring bonds. The structure exhibits only one hydrogen bond between the N*(4) and O*(2) atoms of the cytosine moiety (2.864 Å). The molecules pack in antiparallel chains aligned with theaaxis which are held together by van der Waals forces. The basic unit of each chain consists of two molecules related by the screw axis parallel to a and repeated to form an interconnected hydrogen‐bonded herring

ISSN:0567-7408    

DOI:10.1111/j.1600-5740.1974.tb00008.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

The crystal structure of (NH4)6Mo8O27.4H2O has been determined from three‐dimensional X‐ray diffractometer data and refined to anRindex of 6.4%. The compound was obtained from a concentrated aqueous ammonium heptamolybdate solution after several weeks. It crystallizes in the space groupP21/cwitha= 9519,b= 11,309,c= 15.049 Å, β = 109.50°, andZ= 2. The structure consists of octamolybdate units which are polymerized to infinite chains through one common oxygen atom. The octamolybdate unit is built up of distorted MoO6octahedra sharing edges and corners. Mo‐O bond lengths vary from 1.697 to 2.401 Å, with values of 1.697 to 1.732 Å in the terminal bonds. Mo … Mo distances are 3.258 to 3.472 Å (edge‐sharing), 3.778, 3.970 and 3.980 Å (corner‐sharing). The anion chains are separated by NH4+ions and H2O molecules; a probable network of hydrogen

ISSN:0567-7408    

DOI:10.1111/j.1600-5740.1974.tb00009.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

The molecular structure of NaI. N(CH2CH2OCH3)3(2,2‘,2“‐trimethoxytriethylamine‐sodium iodide complex) has been established by a three‐dimensional single‐crystal X‐ray analysis. The crystals are orthorhombic, space groupPna21with one molecule per asymmetric unit anda= 14.777 (9),b= 7.560 (3),c= 13.570 (3) Å. The structure was solved by the heavy‐atom method from data collected at room temperature on a four‐circle diffractometer using the θ‐2θ scan technique. It was refined by the least‐squares method toR= 0.034 for 1173 observed reflexions. The structure of the five‐coordinated complex of sodium is described and discussed. The crystal structure consists of discrete molecules in which the sodium cation is pentacoordinated. Each sodium atom is bonded to all heteroatoms of one ligand and to the iodine ion. The Na‐N distance is 2.46 Å. The mean value of the Na‐O distances is 2.35

ISSN:0567-7408    

DOI:10.1111/j.1600-5740.1974.tb00010.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY