Refinement of the structure of Mg2As2O7

1970 ◽  
Vol 48 (6) ◽  
pp. 890-894 ◽  
Author(s):  
C. Calvo ◽  
K. Neelakantan
Keyword(s):  
Crystal Structure ◽  
Oxygen Atom ◽  
Least Squares ◽  
Unit Cell ◽  
Full Matrix ◽  
Space Group ◽  
Cell Dimensions ◽  
Central Oxygen ◽  
R Value ◽  
Unit Cell Dimensions

The crystal structure of Mg2As2O7 has been refined by full matrix least squares procedures using 587 observed reflections. The structure of Mg2As2O7 is of the thortveitite type, as reported by Łukaszewicz, with space group C2/m and unit cell dimensions a = 6.567(2) Å, b = 8.524(4) Å, c = 4.739(1) Å, β = 103.8(1)°, and Z = 2. The As—O—As group in the anion appears to be linear but the central oxygen atom undergoes considerable disorder in the plane perpendicular to this group. The AsO bond distances uncorrected for thermal motion are 1.67 Å for the As—O(—As) bond and 1.66 and 1.65 Å for the terminal As—O bonds. The final R value obtained is 0.088.

Refinement of the Crystal Structure of Synthetic Chervetite, Pb2V2O7

1973 ◽  
Vol 51 (1) ◽  
pp. 70-76 ◽  
Author(s):  
Robert D. Shannon ◽  
Crispin Calvo
Keyword(s):  
Crystal Structure ◽  
Least Squares ◽  
Unit Cell ◽  
Type Structure ◽  
Covalent Bonds ◽  
Full Matrix ◽  
Space Group ◽  
Cell Dimensions ◽  
Unit Cell Dimensions

The structure of synthetic chervetite has been refined by full matrix least-squares to a ωR = 0.029 using 1105 reflections. Unit cell dimensions are a = 13.3689(7), b = 7.1607(4), c = 7.1027(4) Å, β = 105935(5)°, and the space group is P21/a. The structure, originally solved by Kawahara, is a dichromate-type structure with a V2O74− group eclipsed to within 11 ± 5°. The Pb2+ ions are irregularly coordinated to 8 or 9 oxygens with distances from 2.40 to 3.20 Å. The distortion of the Pb–O distances is considerably greater than the corresponding distortions of the Sr–O distances in the similar β-Sr2V2O7 structure and is related to the tendency of Pb2+ to form directional covalent bonds. The V–O distances range from 1,665 to 1.720 Å for terminal oxygens and are 1.812 and 1.821 Å for the bridging oxygens. The V–O distances are consistent with the strengths of the Pb—O bonds.

Refinement of the Crystal Structure of the Low-quartz Modification of Ferric Phosphate

1975 ◽  
Vol 53 (14) ◽  
pp. 2064-2067 ◽  
Author(s):  
Hok Nam Ng ◽  
Crispin Calvo
Keyword(s):  
Crystal Structure ◽  
Least Squares ◽  
Room Temperature ◽  
Unit Cell ◽  
Full Matrix ◽  
Space Group ◽  
Ferric Phosphate ◽  
R Value

The structure of ferric phosphate at room temperature was refined on a Dauphiné-twinned crystal using full-matrix least-squares methods. The final R value was 0.078 for 487 symmetry-independent reflections whose intensities were corrected for twinning. The structure was found to be isotypic with AlPO4 (berlinite) with the space group P3121 and four formula units in a unit cell defined by a = 5.036(2) and c = 11.255(4) Å. The structure is also closely related to that of α-quartz with a nearly doubled c-axis because of the ordering of Fe and P atoms. The PO4 tetrahedron is almost regular with a mean P—O distance of 1.526 Å. The Fe3+ ion is tetrahedrally coordinated with an average Fe—O distance of 1.853 Å.

Crystal Structure of Synthetic Mg-Whitlockite, Ca18Mg2H2(PO4)14

1974 ◽  
Vol 52 (7) ◽  
pp. 1155-1164 ◽  
Author(s):  
Ramanathan Gopal ◽  
Crispin Calvo ◽  
Jun Ito ◽  
W. K. Sabine
Keyword(s):  
Crystal Structure ◽  
Oxygen Atom ◽  
Least Squares ◽  
Formula Unit ◽  
Full Matrix ◽  
Space Group ◽  
R Value ◽  
Unit Density ◽  
A Chain ◽  
Automatic Diffractometer

Crystals of synthetic Mg-whitlockite, Ca18Mg2H2(PO4)14, have been grown by hydrothermal techniques and their structure refined by full-matrix least-squares methods, using 1626 unique reflections measured with a Syntex [Formula: see text] automatic diffractometer, to a final R value of 0.046. The crystals have space group R3c with ZR = 1, a = 13.765(8) Å and α = 44.25(5)° with the equivalent hexagonal parameters a = 10.350(5), c = 37.085(12) Å and ZH = 3. The structure, although similar to that of βCa3(PO4)2, differs significantly. The structure contains interconnected infinite chains of polyhedra paralleling the hexagonal c axis with links in the chains consisting of three CaO8 polyhedra separated by two PO4 tetrahedra. Six of these chains surround a chain of MgO6 octahedra and PO4H groups which lie on the three-fold axes. These chains however contain only half the formula unit density of the calcium containing ones and a proton, presumably disordered, is attached to the oxygen atom on the triad axes.

The crystal structure of benzenediazonium tetrafluoroborate, C6H5N2+•BF4−1

1982 ◽  
Vol 60 (22) ◽  
pp. 2852-2855 ◽  
Author(s):  
Miroslaw Cygler ◽  
Maria Przybylska ◽  
Richard MacLeod Elofson
Keyword(s):  
Crystal Structure ◽  
Least Squares ◽  
Benzene Ring ◽  
Positive Charge ◽  
Unit Cell ◽  
Full Matrix ◽  
Bond Lengths ◽  
Cell Dimensions ◽  
Unit Cell Dimensions ◽  
Close Contacts

Benzenediazonium tetrafluoroborate, C6H5N2+•BF4−, crystallizes in space group P21/a with unit cell dimensions a = 17.347(2), b = 8.396(1), c = 5.685(1) Å, β = 92.14(1)°, Z = 4. The structure was solved by direct phasing methods using the program SHELX 76. The parameters were refined by full-matrix least-squares to a final R = 0.063 for 1346 observed reflections. The bond lengths and angles agree very well with those of Rømming for benzenediazonium chloride. The C—N and N≡N bond lengths are 1.415(3) and 1.083(3) Å, respectively, and the bonds of the benzene ring do not show any significant differences as they vary from 1.371(5) to 1.383(4) Å. There are three [Formula: see text] close contacts of ≤ 2.84 Å and the positive charge appears to be shared between the nitrogen atoms.

scholarly journals The Crystal Structure of bis-(μ-N-ethyl-Nphenyldithiocarbamato- S,S’)-bis[(N-ethyl-Nphenyldithiocarbamato- κ2S,S’)zinc(II)]

2021 ◽  
Author(s):  
Robert A Gossage ◽  
Hilary A Jenkins
Keyword(s):  
Crystal Structure ◽  
Metal Atom ◽  
Unit Cell ◽  
Secondary Amines ◽  
Triclinic Crystal System ◽  
Space Group ◽  
Crystal System ◽  
Cell Dimensions ◽  
R Value ◽  
Unit Cell Dimensions

The title material crystallises in the triclinic crystal system in space group P-1 with Z = 2. The unit cell dimensions are a = 8.7365(6)Å, b = 10.6009(7)Å, c = 12.0210(8)Å with α = 66.343(1)°, β = 79.566(1)°, γ = 83.150(1)° and V = 1001.6(1)Å3. The final R value is 0.0307 (3905 observed reflections: I >2σ(I)). The compound is best described as a species in which each metal atom is coordinated to two dithiocarbamato groups, one of which forms a secondary bridging interaction (through a S-atom) to a second [Zn(S2CNEtPh)2] unit. Thus, the title material is in the form of a dimeric aggregate. This complex is compared to related materials which contain N-atoms within the dithiocarbamato ligand that are derived from secondary amines containing two different organic functionalities.

scholarly journals The Crystal Structure of bis-(μ-N-ethyl-Nphenyldithiocarbamato- S,S’)-bis[(N-ethyl-Nphenyldithiocarbamato- κ2S,S’)zinc(II)]

2021 ◽  
Author(s):  
Robert A Gossage ◽  
Hilary A Jenkins
Keyword(s):  
Crystal Structure ◽  
Metal Atom ◽  
Unit Cell ◽  
Secondary Amines ◽  
Triclinic Crystal System ◽  
Space Group ◽  
Crystal System ◽  
Cell Dimensions ◽  
R Value ◽  
Unit Cell Dimensions

The title material crystallises in the triclinic crystal system in space group P-1 with Z = 2. The unit cell dimensions are a = 8.7365(6)Å, b = 10.6009(7)Å, c = 12.0210(8)Å with α = 66.343(1)°, β = 79.566(1)°, γ = 83.150(1)° and V = 1001.6(1)Å3. The final R value is 0.0307 (3905 observed reflections: I >2σ(I)). The compound is best described as a species in which each metal atom is coordinated to two dithiocarbamato groups, one of which forms a secondary bridging interaction (through a S-atom) to a second [Zn(S2CNEtPh)2] unit. Thus, the title material is in the form of a dimeric aggregate. This complex is compared to related materials which contain N-atoms within the dithiocarbamato ligand that are derived from secondary amines containing two different organic functionalities.

The Crystal Structure of a Thiathiophthen Nitrogen Isostere, 3,5-Epidithio-2,5-diphenyl-2,4-pentadienylidene-3-aminoquinoline

1971 ◽  
Vol 49 (2) ◽  
pp. 167-172 ◽  
Author(s):  
F. Leung ◽  
S. C. Nyburg
Keyword(s):  
Crystal Structure ◽  
Least Squares ◽  
Unit Cell ◽  
Full Matrix ◽  
X Ray ◽  
Bond Lengths ◽  
Triclinic System ◽  
R Factor ◽  
Cell Dimensions ◽  
Unit Cell Dimensions

The crystal structure of a thiathiophthen nitrogen isostere (7) has been solved by X-ray analysis. The crystal belongs to the triclinic system with unit cell dimensions: a = 11.275(11), b = 9.558(10), c = 10.797(10) Å, α = 92.50(10), β = 116.98(10), γ = 92.61(10)°. There are two molecules per unit cell, space group [Formula: see text]. The data were collected by diffractometer with CuKα radiation. The structure was solved by symbolic addition procedures, and fully refined anisotropically using full-matrix least squares to an R factor of 6.3%.The S—S and S—N bond lengths were found to be 2.364 and 1.887 Å, respectively. This reveals the partial bonding character between S … S … N atoms.

Kristallstruktur von Bis(N.N′-bis(8-chinoyl)äthylendiaminato)nickel(II) / Crystal Structure of Bis(N,N′-bis(8-chinoyl)ethylenediaminato)nickel(II)

1977 ◽  
Vol 32 (2) ◽  
pp. 131-133 ◽  
Author(s):  
H. Endres ◽  
H. J. Keller ◽  
A. Poveda
Keyword(s):  
Crystal Structure ◽  
Solid State ◽  
Least Squares ◽  
Title Compound ◽  
Unit Cell ◽  
Monoclinic Space Group ◽  
Space Group ◽  
Cell Dimensions ◽  
Planar Molecules ◽  
Unit Cell Dimensions

The title compound NiC20H16N4 crystallizes in the monoclinic space group Ρ21/a with unit cell dimensions a = 12.07(2) Å, b= 10.712(4) Å, c = 13.50(3) Å, β= 113.1(1)°. The structure was refined by a blockmatrix least squares procedure to R = 0.126, based on 1258 observed intensities. The planar molecules form centro-symmetric dimers in the solid state with interplane distances of 3.3 A.

Cyclopentadienyl-Ruthenium and -Osmium Chemistry. XXX. Synthesis and X-Ray Structure of [Ru(dppm-P)(dppm-P,P')(η-C5H5)][PF6]0.5[PO2F2]0.5

1988 ◽  
Vol 41 (4) ◽  
pp. 597 ◽  
Author(s):  
MI Bruce ◽  
MP Cifuentes ◽  
KR Grundy ◽  
MJ Liddell ◽  
MR Snow ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Least Squares ◽  
Phenyl Group ◽  
Unit Cell ◽  
Monoclinic Space Group ◽  
One Pot ◽  
Full Matrix ◽  
X Ray ◽  
Cell Dimensions ◽  
Unit Cell Dimensions

An improved, one-pot synthesis is reported for the [Ru (dppm -P)(dppm -P, P′)(η-C5H5)]+ cation as its BF4- salt. The crystal structure of [Ru ( dppm - P)( dppm -P,P′)(η-C5H5)]+, obtained as the mixed PF6-/PO2F2- salt, has also been determined. There are few differences in dimensions between the mono- and bi-dentate dppm ligands; chelation sharply reduces the P-CH2-P angle, and one phenyl group on each phosphorus is bent away from the metal. Crystals are monoclinic, space group C2/c with unit cell dimensions a 21.743(3), b 23.594(3), c 21.352(3)Ǻ, β 110.17(1) and Z 8. The structure was refined by a full-matrix least-squares procedure to final R 0.078 and Rw 0.087 for 4490 reflections with I > 2.5σ(I).

Crystal structures of phenacylkojate (2-(hydroxymethyl)-5-phenacyloxy-4H-pyran-4-one) and its complex with sodium chloride: bis(phenacylkojate)sodium chloride

1976 ◽  
Vol 54 (17) ◽  
pp. 2723-2732 ◽  
Author(s):  
Simon E. V. Phillips ◽  
James Trotter
Keyword(s):  
Crystal Structure ◽  
Sodium Chloride ◽  
Potassium Iodide ◽  
Unit Cell ◽  
Monoclinic Space Group ◽  
Hydroxyl Groups ◽  
Space Group ◽  
Cell Dimensions ◽  
Unit Cell Dimensions ◽  
Iodide Complex

The structures of the title compounds have been determined by three dimensional X-ray crystal structure analysis.Crystals of anhydrous phenacylkojate are monoclinic, space group P21/c, with unit cell dimensions a = 9.087(4), b = 11.764(3), c = 12.714(4) Å, β = 116.57(2)°, Z = 4. The structure was solved by direct methods and refined by full-matrix least-squares to R = 0.044 for 1225 independent diffractometer observations. The crystal structure is held together by hydrogen bonding between carbonyl and hydroxyl groups and [Formula: see text] interactions.Crystals of the sodium chloride complex are monoclinic, space group C2/c, with unit cell dimensions a = 11.3714(6), b = 15.796(1), c = 14.487(1) Å, β = 97.241(5)°, Z = 4. The structure was solved by heavy atom and Fourier methods and comparison with the previously determined structure of the potassium iodide complex. It was refined to R = 0.040 for 1670 independent diffractometer observations. The structure closely resembles that of the potassium iodide complex (P21/n), but in C2/c, the alkali metal ion being eight co-ordinate in each. Na+—O distances are in the range 2.558–2.674 Å and the [Formula: see text] hydrogen bonded distance is 3.266 Å.

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