scholarly journals The structures of 1:1 and 1:2 adducts of phosphanetricarbonitrile with 1,4-diazabicyclo[2.2.2]octane

2021 ◽  
Vol 77 (12) ◽  
Author(s):  
Andrew P. Purdy ◽  
Ray J. Butcher ◽  
Christopher A. Klug
Keyword(s):  
Phosphorus Atom ◽  
Triple Bond ◽  
Lone Pair ◽  
Molecular Geometry ◽  
Mirror Plane ◽  
Monoclinic Space Group ◽  
Orthorhombic Space Group ◽  
Space Group ◽  
Distorted Octahedral ◽  
Lone Pair Electrons

In the structures of 1:1 and 1:2 adducts of phosphanetricarbonitrile (C3N3P) with 1,4-diazabicyclo[2.2.2]octane (C6H12N2), the 1:1 adduct crystallizes in the orthorhombic space group, Pbcm, with four formula units in the unit cell (Z′ = 0.5). The P(CN)3 unit lies on a crystallographic mirror plane while the C6H12N2 unit lies on a crystallographic twofold axis passing through one of the C—C bonds. The P(CN)3 moiety has close to C 3v symmetry and is stabilized by forming adducts with two symmetry-related C6H12N2 units. The phosphorus atom is in a five-coordinate environment. As a result of the symmetry, the two trans angles are equal so τ5 = 0.00 and thus the geometrical description could be considered to be square pyramidal. However, the electronic geometry is distorted octahedral with the lone pair on the phosphorous occupying the sixth position. As would be expected from VSEPR considerations, the repulsion of the lone-pair electrons with the equatorial bonding electrons means that the trans angles for the latter are considerably reduced from 180° to 162.01 (4)°, so the best description of the overall geometry for phosphorus is distorted square pyramidal. The 1:2 adduct crystallizes in the monoclinic space group, P21/m with two formula units in the asymmetric unit (i.e. Z' = 1/2). The P(CN)3 moiety lies on a mirror plane and one of the two C6H12N2 (dabco) molecules also lies on a mirror plane. The symmetry of the P(CN)3 unit is close to C 3v. There are three P...N interactions and consequently the molecular geometry of the phosphorus atom is distorted octahedral. This must mean that the lone pair of electrons on the phosphorus atom is not sterically active. For the 1:1 adduct, there are weak associations between the phosphorus atom and one of the terminal nitrogen atoms from the C[triple-bond] N moiety, forming chains in the a-axis direction. In addition there are weak C—H...N interactions between a terminal nitrogen atoms from the C[triple-bond]N moiety and the C6H12N2 molecules, which form sheets perpendicular to the a axis.

scholarly journals Die Kristallstrukturen von (1,5-Ditolylpentaazadienido)(triphenylphosphan)gold(I) und 1,5-Ditolyl-3-methylpentaazadien / The Crystal Structures of (1,5-Ditolylpentaazadienido)(triphenylphosphane)gold(I) and 1,5-Ditolyl-3-methylpentaazadien

1988 ◽  
Vol 43 (10) ◽  
pp. 1219-1223 ◽  
Author(s):  
Johannes Beck
Keyword(s):  
Nitrogen Atom ◽  
Crystal Structures ◽  
Phosphorus Atom ◽  
Gold Atom ◽  
Monoclinic Space Group ◽  
Orthorhombic Space Group ◽  
Space Group ◽  
Lattice Constants ◽  
Monomeric Complex ◽  
Single Bonds

PPh3Au(tolN5tol) is obtained by the reaction of PPh3Au+ClO4- with Tl(tolN5tol). It crystallizes in the monoclinic space group P21/c with the lattice parameters a = 1548.8(5), b = 1070.7(2), c = 1779.1(3) pm, β = 90.33(2)°, Z = 4. In the monomeric complex the gold atom is nearly linearcoordinated by the phosphorus atom of the PPh3 group and nitrogen atom N3 of the pentaazadienido ligand ( N3 - Au - P 178.4°). tolNN(NCH3)NNtol crystallizes in the orthorhombic space group Pccn with the lattice constants a = 2426.7(9), b = 469.3(2), c = 1195.3(4) pm. The unit cell contains four molecules, located on twofold axes. Due to the isolobality of the CH3 and the PPh3Au group, the two structures are closely related. Both contain the typical planar zig-zag chain of five nitrogen atoms with located double bonds N1-N2 and N4 - N5 (from 119.8 to 126.6 pm) and shortened single bonds N2 - N3 and N3 - N4 (132.7 to 140.0 pm).

scholarly journals A variable-temperature study of a phase transition in barbituric acid dihydrate

2005 ◽  
Vol 61 (4) ◽  
pp. 464-472 ◽  
Author(s):  
Gary S. Nichol ◽  
William Clegg
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
Barbituric Acid ◽  
Crystal Packing ◽  
Variable Temperature ◽  
Mirror Plane ◽  
Monoclinic Space Group ◽  
Orthorhombic Space Group ◽  
Acta Cryst ◽  
Space Group

The crystal structure of barbituric acid dihydrate (C4H4N2O3·2H2O) has twice been reported as orthorhombic, space group Pnma, with all atoms (except for CH2 H atoms) lying on the mirror plane [Al-Karaghouli et al. (1977). Acta Cryst. B33, 1655–1660; Jeffrey et al. (1961). Acta Cryst. 14, 881–887]. The present study has found that at low temperatures, below 200 K, the crystal structure is no longer orthorhombic but is non-merohedrally twinned monoclinic, space group P21/n. This phase is stable down to 100 K. Above 220 K the crystal structure is orthorhombic, and between 200 and 220 K the structure undergoes a phase change, with the monoclinic-to-orthorhombic phase transition itself taking place at around 216–217 K. The size of the β angle in the monoclinic structure is temperature dependent; at 100 K β is around 94° and it decreases in magnitude towards 90° as the temperature increases. Although the hydrogen-bonding motifs are the same for both crystal systems, there are significant differences in the crystal packing, in particular the out-of-plane displacement of the two water molecules and the sp 3-hybridized C atom of barbituric acid.

On the Stereochemistry of the Lone-Pair Electrons in AX6E-Systems: Dynamically Distorted Anion in (NH4)2SeBr6, Statically Distorted Anion in 1,3-Propanediammonium-Hexabromoselenate(IV) (C3N2H12)SeBr6

1987 ◽  
Vol 42 (4) ◽  
pp. 415-420 ◽  
Author(s):  
Walter Abriel
Keyword(s):  
Single Crystal ◽  
Lone Pair ◽  
Structural Data ◽  
Point Symmetry ◽  
Intensity Data ◽  
Orthorhombic Space Group ◽  
Space Group ◽  
X Ray ◽  
Lone Pair Electrons ◽  
Acta Crystallogr

Abstract Using 293 K diffractometer intensity data, the crystal structures of (NH4)2SeBr6 (1) and [H3N(CH2)3NH3]SeBr6 (2) have been determined by single crystal X-ray technique and refined to a final Rw of 0.049 and 0.040, respectively. The dark red crystals of 1 are cubic (space group Fm3m) with a = 10.478(2) Å and Z = 4. This structure contains SeBe62- octahedra (point symmetry m3̄m, distance Se-Br: 2.577(2) Å in an antifluorite type arrangement of cations and anions. In contrast, the SeBr fi 2-ion in 2 is statically distorted (approximate point symmetry 3m, distance Se-Br min. 2,547(2), max. 2.595(2) Å. The dark red crystals are orthorhombic (space group Pnma) with a = 17.795(3), b = 7.5037(6), c = 10.476(1) Å and Z = 4. The results agree with the rules for the appearance of a static/dynamic stereochemical effect of the lone pair electrons given for TeX62- (X = Cl, Br, I) species (W. Abriel, Acta Crystallogr. B 42, 449 (1986)). Consequently these rules can be extended considering SeX62- as well. Basic structural data for all compounds containing AX62- ions (A = Se, Te; X = Cl, Br, I) known to date are given including the ⊿-values (R. D. Shannon, Acta Crystallogr. A 32, 751 (1976)) as a measure for the distortion of the octahedral anion.

scholarly journals Zur Stereochemie des freien Elektronenpaares in AX6E-Systemen, IX+ Statisch verzerrtes Anion in [(CH3)2HN(C6H4)NH(CH3)2]TeCl6 / On the Stereochemistry of the Lone-Pair Electrons in AX6E-Systems, IX+ Statically Distorted Anion in [(CH3)2HN(C6H4)NH(CH3)2]TeCl6

1990 ◽  
Vol 45 (5) ◽  
pp. 573-578 ◽  
Author(s):  
André du Bois ◽  
Walter Abriel
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonding ◽  
Single Crystal ◽  
Lone Pair ◽  
Intensity Data ◽  
Orthorhombic Space Group ◽  
Space Group ◽  
X Ray ◽  
Lone Pair Electrons ◽  
Symmetry Rules

Using 293 K diffractometer intensity data, the crystal structure of [(CH3)2HN(C6H4)NH(CH3)2]TeCl6 has been determined by single crystal X-ray technique and refined to a final Rw of 0.022. The yellow crystals are orthorhombic, space group Pna 21, with a = 17.565(2), b = 8.4496(6), c = 12.572(1) Å and Z = 4. The TeCl62- anions show a strong statical distortion with Te—Cl distances from min. 2.39 to max. 2.78 A. The symmetry rules for the stereochemistry of the lone pair electrons in AX6E-systems are confirmed. The influence of hydrogen bonding on the type of distortion is also discussed.

The Crystal Structures of [N,N’-Bis(3-methoxysalicylidene)-1,3- diaminopropane]nickel(II) and -copper(II)

2004 ◽  
Vol 59 (2) ◽  
pp. 228-232 ◽  
Author(s):  
Ayhan Elmali ◽  
Celal T Zeyrek ◽  
Yalcin Elerman
Keyword(s):  
Crystal Structures ◽  
Mirror Symmetry ◽  
Distorted Octahedral Geometry ◽  
Planar Geometry ◽  
Water Molecules ◽  
Monoclinic Space Group ◽  
Orthorhombic Space Group ◽  
Space Group ◽  
Bond Lengths ◽  
Distorted Octahedral

[N,N′’-Bis(3-methoxysalicylidene)-1,3-diaminopropane]nickel(II) dihydrate [Ni(C19H20N2O4)· 2(H2O)] 1 and [N,N′-bis(3-methoxysalicylidene)-1,4-diaminobutane]copper(II) [Cu(C20H22N2O4)] 2 have been synthesized and their crystal structures determined. Crystals of compound 1 are orthorhombic, space group Pnma, a = 7.509(3), b = 22.070(7), c = 11.532(4) Å, V = 1611.1(12) Å3, Z = 4 and Dc = 1.498 g·cm−3. The molecule 1 has mirror symmetry, but the ligand is not planar. The two parts of the Schiff base moieties are folded so as to form an angle of 21.6(1)°. The Ni atom is in a distorted octahedral geometry and coordinated by the donor atoms of the ligand in the horizontal plane and of two water molecules. Crystals of compound 2 are monoclinic, space group P21/c, a = 9.488(1), b = 21.918(3), c = 8.413(1) Å, β = 91.45(1)°, V = 1749.0(4) Å3, Z = 4 and Dc = 1.587 g·cm−3. The Cu atom is coordinated by an N2O2 donor set from the imine-phenol ligand in a distorted planar geometry, with the two phenolate O atoms deprotonated. The Cu-O bond lengths are 1.854(3) and 1.868(3)Å . The Cu-N bond lengths are 1.931(3) and 1.950(3) Å, the dihedral angle between the two 3-methoxysalicylidene groups is 43.4(1)°.

Structures of L-valyl-L-glutamine and L-glutamyl-L-valine

1996 ◽  
Vol 52 (6) ◽  
pp. 999-1006 ◽  
Author(s):  
C. H. Görbitz ◽  
P. H. Backe
Keyword(s):  
Hydrogen Bond ◽  
Crystal Packing ◽  
Molecular Geometry ◽  
Side Chain ◽  
Monoclinic Space Group ◽  
Orthorhombic Space Group ◽  
Acta Cryst ◽  
Space Group ◽  
Cell Parameters ◽  
Additional Hydrogen Bond

L-Val-L-Gln crystallizes in the orthorhombic space group P21212 with a = 16.419 (3), b = 15.309 (3) and c = 4.708 (1) Å. The final wR(F o 2) is 0.100 for 2044 independent reflections, R(Fo ) = 0.050 for 1475 reflections with I > 2.0σ(I). L-Glu-L-Val crystallizes in the monoclinic space group P21 with a = 6.487 (2), b = 5.505 (2), c = 16.741 (4) Å and β = 97.22 (2)°. The final wR(F F o 2) is 0.111 for 1920 independent reflections, R(Fo ) = 0.047 for 1576 reflections with I > 2.0σ(I). Molecular geometries are normal, except for a unique eclipsed orientation of the charged amino group of L-Glu-L-Val. Dipeptides with a N-terminal hydrophobic residue and C-terminal hydrophilic residue are shown to have crystal packing patterns fundamentally different from those of dipeptides with the same types of residues in reversed order. Accordingly, the structure of L-Val-L-Glu [Eggleston (1984). Acta Cryst. C40, 1250 –1252] is rather similar to L-Val-L-Gln, but different from its retroanalogue L-Glu-L-Val. Nevertheless, the pairing of hydrogen-bond donors and acceptors is the same for L-Val-L-Glu and L-Glu-L-Val, indicating very distinct hydrogen-bonding preferences. This is the first demonstration of such a coincidence among dipeptide structures. The differences between L-Val-L-Glu and L-Val-L-Gln structures stem from modifications of the molecular geometry and cell parameters due to the formation of an additional hydrogen bond from the extra donor in the L-Gln side chain.

On the Crystal Structure of Bi2Te4O11

1992 ◽  
Vol 45 (9) ◽  
pp. 1415 ◽  
Author(s):  
HJ Rossell ◽  
M Leblanc ◽  
G Ferey ◽  
DJM Bevan ◽  
DJ Simpson ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Lone Pair ◽  
Lattice Parameters ◽  
Powder Pattern ◽  
Monoclinic Space Group ◽  
Space Group ◽  
X Ray ◽  
Fluorite Type ◽  
Lone Pair Electrons

Bi2Te4O11 is monoclinic, space group P21/n; the lattice parameters derived from a Guinier powder pattern ( Si standard) are: a = 6.9909(3), b = 7.9593(3), c = 18.8963(8) � , β = 95.176(3)�, Z = 4, V = 1047.15 �. The structure was solved independently from both single-crystal X-ray data and a combination of X-ray and neutron powder data. It is an anion-deficient superstructure of fluorite in which can be recognized the ordered intergrowth of fluorite-type Bi2Te2O7 and rutile-type Te2O4. Lone-pair electrons are stereochemically active.

Zur Stereochemie des freien Elektronenpaares in Verbindungen des vierwertigen Tellurs: Verzerrtes TeCI62-Oktaeder in [H3N(CH2)3NH3TeCI6 regulär oktaedrisches Anion in H3N(CH2)3NH3SnCI6 / On the Stereochemistry of Lone Pair Electrons in Compounds with Tetravalent Tellurium: Distorted TeCl62-Octahedron in [H3N(CH2)3NH3]TeCl6, Regular Octahedral Anion in [H3N(CH2)3NH3]SnCl6

1985 ◽  
Vol 40 (12) ◽  
pp. 1691-1697 ◽  
Author(s):  
Walter Abriel ◽  
Claudia Friedrich
Keyword(s):  
Single Crystal ◽  
Lone Pair ◽  
Point Symmetry ◽  
Intensity Data ◽  
Orthorhombic Space Group ◽  
Small Deviations ◽  
Space Group ◽  
X Ray ◽  
Lone Pair Electrons

Abstract Using 293 K diffractometer intensity data, the structures of [H3N(CH2)3NH3]TeCl6 and [H3N(CH2)3NH3]SnCl6 have been determined by single crystal X-ray technique and refined to a final of 0.027 and 0,029, respectively. The yellow crystals of the tellurate are orthorhombic (space group Pnma) with a = 22.952(2), b = 7.5414(4), c - 7.801(1) Å and Z = 4. This structure contains distorted TeCl62- octahedra (distances Te - Cl min. 2.426(1), max. 2.672(1) Å ) with approximate 2mm point symmetry. In contrast, the SnCl62- ion in the second title com pound is octahedral with only small deviations from m 3m symmetry (distances Sn -Cl mean: 2.438(3) Ä ). The colourless crystals of this tin com pound are orthorhombic (space group Pnma) with a - 17.6082(9), b = 7.1809(3), c = 10.190(1) Å and Z = 4. Considering the TeX62- (X = Cl, Br, I) salts known to date, a distorted species is an exception, although a distortion is predicted by the VSEPR theory. The results agree with the rules for the appearance of a static stereochemical effect of the lone pair electrons in the TeX62- species

Strukturuntersuchungen an Diaryldichalkogeniden: Die Molekülstrukturen von [2,4,6-(CF3)3C6H2S]2,[2,4,6-Me3C6H2Te]2 und [2-Me2N-4,6-(CF3)2C6H2Te]2 / Structural Investigations of Diaryl Dichalcogenides: The Molecular Structures of [2,4,6-(CF3)3C6H2S]2, [2,4,6-Me3C6H2Te]2 and [2-Me2N-4,6-(CF3)2C6H2Te]2

1992 ◽  
Vol 47 (3) ◽  
pp. 305-309 ◽  
Author(s):  
Anja Edelmann ◽  
Sally Brooker ◽  
Norbert Bertel ◽  
Mathias Noltemeyer ◽  
Herbert W. Roesky ◽  
...  
Keyword(s):  
Molecular Structures ◽  
Monoclinic Space Group ◽  
Crystal Data ◽  
X Ray Diffraction ◽  
Orthorhombic Space Group ◽  
Structural Investigations ◽  
Space Group ◽  
X Ray

Abstract The Molecular Structures of [2,4,6-(CF3)3C6H2S]2 (1) [2,4,6-Me3C6H2Te]2 and [2-Me2N-4,6-(CF3)2C6H2Te]2 (3) have been determined by X-ray diffraction. Crystal data: 1: orthorhombic, space group P212121, Z = 4, a = 822.3(2), b = 1029.2(2), c = 2526.6(5) pm (2343 observed independent reflexions, R = 0.042); 2: orthorhombic, space group Iba 2, Z = 8, a = 1546.5(2), b = 1578.4(2), c = 1483.9(1) pm (2051 observed independent reflexions, R = 0.030); 3: monoclinic, space group P 21/c, Z = 4, a = 1118.7(1), b = 1536.5(2), c = 1492.6(2) pm, β = 98.97(1)° (3033 observed independent reflexions, R = 0.025).

Two lithium tricyanomethanide compounds: syntheses and single-crystal structure determination of LiK[C(CN)3]2 and Li[C(CN)3]·½ (H3C)2CO

2015 ◽  
Vol 70 (3) ◽  
pp. 191-196 ◽  
Author(s):  
Olaf Reckeweg ◽  
Francis J. DiSalvo
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Single Crystals ◽  
Structure Determination ◽  
Monoclinic Space Group ◽  
Orthorhombic Space Group ◽  
Space Group ◽  
Cell Parameters ◽  
New Compounds

AbstractThe new compounds LiK[C(CN)3]2 and Li[C(CN)3]·½ (H3C)2CO were synthesized and their crystal structures were determined. Li[C(CN)3]·½ (H3C)2CO crystallizes in the orthorhombic space group Ima2 (no. 46) with the cell parameters a=794.97(14), b=1165.1(2) and c=1485.4(3) pm, while LiK[C(CN)3]2 adopts the monoclinic space group P21/c (no. 14) with the cell parameters a=1265.7(2), b=1068.0(2) and c=778.36(12) pm and the angle β=95.775(7)°. Single crystals of K[C(CN)3] were also acquired, and the crystal structure was refined more precisely than before corroborating earlier results.

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