Absolute configurations of Emycin D, E and F; mimicry of centrosymmetric space groups by mixtures of chiral stereoisomers

1999 ◽  
Vol 55 (4) ◽  
pp. 607-616 ◽  
Author(s):  
Martina Walker ◽  
Ehmke Pohl ◽  
Regine Herbst-Irmer ◽  
Martin Gerlitz ◽  
Jürgen Rohr ◽  
...  
Keyword(s):  
Correct Choice ◽  
Unit Cell ◽  
Monoclinic Space Group ◽  
Space Group ◽  
Space Groups ◽  
Centrosymmetric Space Group ◽  
Distance Restraints ◽  
Similar Distance ◽  
Triclinic Unit Cell ◽  
R Factors

The crystal structures of Emycin E (1), di-o-bromobenzoyl-Emycin F (2) and o-bromobenzoyl-Emycin D (3) have been determined by X-ray analysis at low temperature. Emycin E and o-bromobenzoyl-Emycin D both crystallize with two molecules in a triclinic unit cell. These two structures can be solved and refined either in the centrosymmetric space group P\bar 1, with apparent disorder localized at or around the expected chiral centre, or in the non-centrosymmetric space group P1 as mixtures of two diastereomers without disorder. Only the latter interpretation is consistent with the chemical and spectroscopic evidence. Refinements in the centrosymmetric and non-centrosymmetric space groups are compared in this paper and are shown to favour the chemically correct interpretation, more decisively so in the case of the bromo derivative as a result of the anomalous dispersion of bromine. Structures (1) and (3) provide a dramatic warning of the dangers inherent in the conventional wisdom that if a structure can be refined satisfactorarily in both centrosymmetric and non-centrosymmetric space groups, the former should always be chosen. In these two cases, despite apparently acceptable intensity statistics and R factors (5.87 and 3.55%), the choice of the centrosymmetric space group leads to the serious chemical error that the triclinic unit cell contains a racemate rather than two chiral diastereomers! The weakest reflections are shown to be most sensitive to the correct choice of space group, underlining the importance of refining against all data rather than against intensities greater than a specified threshold. The use of similar-distance restraints is shown to be beneficial in both P1 refinements. Di-o-bromobenzoyl-Emycin F crystallizes in the monoclinic space group P21 with one molecule in the asymmetric unit and so does not give rise to these problems of interpretation. The absolute configuration of the two bromo derivatives, and hence the Emycins in general, was determined unambiguously as S at the chiral centre C3.

Primäre und sekundäre Ethyl-und i-Propylsulfoniumsalze sowie Kristallstruktur von i-C3H7SH2+SbF6- [1]

1996 ◽  
Vol 51 (2) ◽  
pp. 277-285
Author(s):  
Rolf Minkwitz ◽  
Ulrike Lohmann ◽  
Hans Preut
Keyword(s):  
Crystal Structure ◽  
Structure Analysis ◽  
Bond Distance ◽  
Crystal Structure Analysis ◽  
Unit Cell ◽  
Monoclinic Space Group ◽  
Spectroscopic Methods ◽  
Sulfonium Salt ◽  
Space Group

Abstract The synthesis of salts of the type RnSH3-n+MF6- (R = C2H5, i-C3H7; n = 1, 2; M = As, Sb) by protonation of the corresponding thiols and sulfides in the superacid systems HF/MF5 is reported. The salts have been characterized by vibrational and NMR spectroscopic methods. Isopropylsulfonium hexafluoroantimonate is the first known example of a sulfonium salt, for which a SH bond distance has been determined by a crystal structure analysis, i-C3H7SH2+SbF6- crystallizes in the monoclinic space group P21/m with a = 568.0(4), b = 801.1(6), c = 1019.7(8) pm, β = 82.63(6) °, with two formula units per unit cell.

Methansulfinylchlorid-Lewissäure-Addukte CH3S(Cl)OMF5 (M = As, Sb) und Kristallstruktur von CH3S(Cl)OSbCl5 [1] / Methanesulfinylchloride Lewis Acid Adducts CH3S(Cl)OMF5 (M = As, Sb) and Crystal Structure of CH3S(Cl)OSbCl5 [1]

1996 ◽  
Vol 51 (1) ◽  
pp. 133-138 ◽  
Author(s):  
Rolf Minkwitz ◽  
Ulrike Lohmann ◽  
Hans Preut
Keyword(s):  
Crystal Structure ◽  
Nmr Spectroscopy ◽  
Lewis Acid ◽  
Unit Cell ◽  
Monoclinic Space Group ◽  
Space Group ◽  
New Compounds ◽  
Lewis Acid Adducts

Abstract CH3S(0)C1 reacts in HF as solvent with MF5 (M = As, Sb) to give products CH3S(Cl)OMF5 (M = As, Sb). The new compounds are stable below 253 K and were charac­ terized by Raman and NMR spectroscopy.In addition, the crystal structure of CH3S(Cl)OSbCl5 has been determinated. The complex crystallizes in the monoclinic space group P21/n with a = 644.3(5), b = 1905.9(14), c = 900.0(7) pm, β = 99.27(6)° with four formula units per unit cell.

Anionische Komplexe [Mo2(O2CPh)4X2]2⊖ mit X = N3, Cl, Br. Die Kristallstruktur von (PPh4)2[Mo2(O2CPh)4Cl2] · 2CH2Cl2 / Anionic Complexes [Mo2(O2C-Ph)4X2]2⊖ with X = N3, Cl, Br. The Crystal Structure of (PPh4)2[Mo2(O2C-Ph)4Cl2] · 2CH2Cl2

1985 ◽  
Vol 40 (1) ◽  
pp. 13-18 ◽  
Author(s):  
Kay Jansen ◽  
Kurt Dehnicke ◽  
Dieter Fenske
Keyword(s):  
Crystal Structure ◽  
Ir Spectra ◽  
Diffraction Data ◽  
Unit Cell ◽  
Monoclinic Space Group ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
Lattice Constants ◽  
Anionic Complexes

The syntheses and IR spectra of the complexes [Mo2(O2C-Ph)4X2]2⊖ with X = N3, CI, Br and the counter ion PPh4⊕ are reported. The azido and the bromo complexes are obtained from a solution of [Mo2(O2CPh)4] with PPh4N3 in pyridine or by reaction with PPh4Br in CH2Br2, respectively. When (PPh4)2[Mo2(O2CPh)4(N3)2] is dissolved in CH2Cl2, nitrogen is evolved and the complex with X = CI is obtained. The crystal structure of (PPh4)2[Mo2(O2CPh)4Cl2] · 2CH2Cl2 was determined from X-ray diffraction data (5676 observed independent reflexions, R = 0.042). It crystallizes in the monoclinic space group P21/n with four formula units per unit cell; the lattice constants are a = 1549, b = 1400, c = 1648 pm, β = 94.6°. The centrosymmetric [Mo2(O2CPh)4Cl2]2⊖ ion has a rather short Mo-Mo bond of 213 pm, whereas the MoCl bonds are very long (288 pm)

Reaktionen von Oxo-Rhenium(VII und V)-Verbindungen mit Thiobenzoylhydrazin. Kristall- und Molekülstrukturen von Re(NHNC(S)Ph)3 · DMF, Re(NHNC(S)Ph)3 · OPPh3 und [Re(NHNC(S)Ph)(NHNHC(S)Ph)2]Cl · 1/3 C2H5OH · 1/3 H2O / Reactions of Oxorhenium(VII and V) Complexes with Thiobenzoylhydrazine. Crystal and Molecular Structures of Re(NHNC(S)Ph)3 · DMF, Re(NHNC(S)Ph)3 · OPPh3 and [Re(NHNC(S)Ph)(NHNHC(S)Ph)2]Cl · 1/3 C2H5OH · 1/3 H2O

1990 ◽  
Vol 45 (8) ◽  
pp. 1167-1176 ◽  
Author(s):  
Alfons Möhlenkamp ◽  
Rainer Mattes
Keyword(s):  
Unit Cell ◽  
Molecular Structures ◽  
Monoclinic Space Group ◽  
Chelating Ligands ◽  
Rhenium Atom ◽  
Coordination Polyhedra ◽  
Space Group ◽  
Crystal And Molecular Structures ◽  
Ligand Structure

The reaction of NaReO4 with thiobenzoylhydrazine yields Re(NHNC(S)Ph)3- DMF (1). With ReOCl3(PPh3)2 thiobenzoylhydrazine reacts to give Re(NHNC(S)Ph)3 · OPPh3 (2) and in the presence of HCl to yield [Re(NHNC(S)Ph)(NHNHC(S)Ph),]Cl · 1/3 C2H5OH -1 /3 H2O (3). The structures of 1-3 have been determined. 1: monoclinic, space group P2,/c, a = 1150.1(9), b = 2050.0(9), c = 1181.0(8) pm, β = 109.62(5)°, Z = 4, 2980 reflections, R = 0.055; 2: trigonal, space group R 3, a = 1399.8(1), c = 1684.0(1) pm, Z = 3, 1419 reflections, R = 0.033; 3: monoclinic, space group P2,/c, a = 1446.8(3), b = 3220.7(5), c = 1727.1(4) pm, β = 108.42(2)°, Z = 12, 6112 reflections, R = 0.062. In 1 and 2 three N,S-chelating ligands NHNR (R = C(S)Ph) are coordinated to the central rhenium atom. The ligand structure is intermediate between a diazene and a hydrazido(2–) structure. In 3 each rhenium atom is coordinated by one NHNR and two NHNHR ligands, all N,S-chelating. The latter can be considered as protonated diazene ligands. The unit cell contains three isomeric coordination polyhedra.

Notizen: Solid State Structure of N,N-Dibenzylhydroxylamine

1995 ◽  
Vol 50 (4) ◽  
pp. 699-701 ◽  
Author(s):  
Norbert W. Mitzel ◽  
Jürgen Riede ◽  
Klaus Angermaier ◽  
Hubert Schmidbaur
Keyword(s):  
Solid State ◽  
Hydrogen Bonds ◽  
Single Crystal ◽  
Unit Cell ◽  
Monoclinic Space Group ◽  
State Structure ◽  
X Ray Diffraction ◽  
Space Group ◽  
Solid State Structure ◽  
X Ray

The solid-state structure of N,N-dibenzylhydroxylamine (1) has been determined by single crystal X-ray diffraction. The compound crystallizes in the monoclinic space group P 21/n with four formula units in the unit cell. N,N-dibenzylhydroxylamine dimerizes to give N2O2H2 sixmembered rings as a result of the formation of two hydrogen bonds O - H ··· N in the solid state.

[Al2P4]6-, [Al2As4]6-, [Ga2P4]6- und [Ga2As4]6-, Zintl-Anionen mit 1,3-Dimethylencyclobutan-Struktur / [Al2P4]6-, [Al2As4]6-, [Ga2P4]6- and [Ga2As4]6-, Zintl Anions with 1.3-Dimethylene-cyclobutane Structure

1991 ◽  
Vol 46 (6) ◽  
pp. 789-794 ◽  
Author(s):  
M. Somer ◽  
D. Thiery ◽  
K. Peters ◽  
L. Walz ◽  
M. Hartweg ◽  
...  
Keyword(s):  
Bond Order ◽  
Factor Group ◽  
Unit Cell ◽  
Normal Coordinate Analysis ◽  
Monoclinic Space Group ◽  
Partial Structure ◽  
Normal Coordinate ◽  
Space Group ◽  
Single Bonds ◽  
Fir Spectra

The compounds Cs6M2X4 (M = Al, Ga; X = P, As) were synthesized from stoichiometric mixtures of Cs, M and Cs4X6 in sealed Nb ampoules at 950 K. They are isotypic and crystallize in the monoclinic space group P21/c (No. 14) with Z = 4 formula units per unit cell. The anion partial structure is characterized by isolated [M2X4]6- units with relatively short distances for the terminal d(M–X) bonds corresponding to a Pauling Bond Order PBO = 1.5. The distances d(M–X) of the four-membered M2X2 rings correspond to single bonds.The FIR spectra have been interpreted on the basis of the [M2X4]6- units with 2/m 2/m 2/m-D2h, symmetry by considering a factor group splitting. The assignment of the observed frequencies is supported by a normal coordinate analysis.

Synthese von zweikernigen Triazenido- und Pentaazadienidokomplexen des einwertigen Silbers. Kristallstruktur von [Ag(MeOC6H4N3C6H4OM e)]2· 2/3 Py, [Ag(MeOC6H4N5C6H4OMe)]2 und [Ag(EtOC6H4N5C6H4OEt)]2 · Py / Dimeric Triazenido and Pentaazadienido Complexes of Monovalent Silver. Synthesis and Structure of [Ag(MeOC6H4N3C6H4OM e)]2· 2/3 Pyridine, [Ag(MeOC6H4N5C6H4OMe)]2 und [Ag(EtOC6H4N5C6H4OEt)]2 · Pyridine

1989 ◽  
Vol 44 (7) ◽  
pp. 778-785 ◽  
Author(s):  
Edmund Hartmann ◽  
Raimund Schmid ◽  
Joachim Strähle
Keyword(s):  
Unit Cell ◽  
Dinuclear Complexes ◽  
Monoclinic Space Group ◽  
Triclinic Space Group ◽  
Space Group ◽  
Bridging Ligand ◽  
Orange Yellow ◽  
Ag Contact ◽  
Saturated Solutions

[Ag(MeOC6H4N3C6H4OMe)]2 (1) is formed in THF from AgNO3 , and the triazenide anion, as obtained from the corresponding triazene and Na. 1 crystallizes from pyridine in the form of orange-yellow , air stable crystals with the com position 1·2/3 C5H5N: space group P 1̅ with a = 1468.0(5), b = 1514.1(6), c - 1316.1(3) pm, a = 113.45(3)°, β = 1 1 4 .8 1 (2 )°, γ = 66.78(3)°, Z - 3. The triazenide ion functions as a bridging ligand forming planar (AgN3)2 heterocycles. The unit cell contains two symmetry-independent dinuclear complexes, one of which is centrosymmetrical. The short Ag -Ag distances of 268.0 and 269.8 pm suggest Ag -Ag bonding. The pentaazadienido complexes Ag(RN5R) with R = p -MeO - C6H4 (2), p -EtO - C6H4 (3), p-Cl -C6H4 (4), p -F -C6H4 (5), are obtained from saturated solutions of the pentaazadiene in conc. NH3 and AgNO3 , as explosive, red precipitates which are stable in air. Crystals of 2 and 3 · C5H5N are obtained from pyridine. 2 crystallizes in the monoclinic space group P21/c: a - 583.7(6), b = 1705.1(9), c = 1489.6(9) pm. β = 96.2(1)°, Z = 2; 3 · C5H5N is triclinic (space group P 1̅) with a = 1160.4(4). b = 1671.0(6), c = 509.0(1) pm. a = 97.51(2)°, β = 97.36(2)°, γ = 81.51(3)°, Z = 1. The complexes 2 and 3 are dinuclear with the pentaazadienide ion as a (N1)-η1,(N5)-η1 bridging ligand in 2 and a (N1)-η1, (N3)-η1 bridging ligand in 3. The bridging mode in 3 results in a short Ag -Ag contact of 283.44 pm. The Ag -N distances range from 210.8 to 215.7 pm in 1 and from 215.0 to 220 pm in (2) and (3).

Notizen: Eine neue bicyclische Zinn-Selen-Verbindung. Synthese und Kristallstruktur von [{Cp(CO)2Fe}3ClSn3Se4] / A New Bicyclic Tin Selenium Compound. Synthesis and Crystal Structure of [{Cp(CO)2Fe}3ClSn3Se4]

1993 ◽  
Vol 48 (7) ◽  
pp. 1009-1012 ◽  
Author(s):  
Kurt Merzweiler ◽  
Harald Kraus
Keyword(s):  
Crystal Structure ◽  
Structure Determination ◽  
Unit Cell ◽  
Monoclinic Space Group ◽  
Synthesis And Crystal Structure ◽  
Selenium Compound ◽  
Space Group ◽  
X Ray ◽  
Lattice Constants ◽  
Compound Synthesis

[{Cp(CO)2Fe}SnCl3] reacts with Na2Se in THF to form the compound [{Cp(CO)2Fe}3ClSn3Se4] 1. 1 crystallizes in the monoclinic space group P21/n with 4 formula units per unit cell. The lattice constants are α = 1435.2(7), b = 1124.4(4), c = 1972.7(12) pm, β = 94.59(4)°. According to the X-ray structure determination 1 contains a bicyclic Sn3Se4 framework.

Organolanthanoids. XI. The Crystal and Molecular Structures of Two Tris(η5-cyclopentadienyl)(pyridine) lanthanoid(III) Compounds

1987 ◽  
Vol 40 (5) ◽  
pp. 907 ◽  
Author(s):  
GB Deacon ◽  
BM Gatehouse ◽  
SN Platts ◽  
DL Wilkinson
Keyword(s):  
Crystal Structures ◽  
Coordination Number ◽  
Unit Cell ◽  
Molecular Structures ◽  
Monoclinic Space Group ◽  
Space Group ◽  
Crystal And Molecular Structures

The crystal structures of tris (η5-cyclopentadienyl) (pyridine) samarium(III), monoclinic, space group P21/c, a 10.906(4), b 8.636(2), c 17.825(3) �, β 96.44(2)�, Z 4, R 0.027 and Rw 0.032 for 3619 'observed' reflections, and tris (η5-cyclopentadienyl)(pyridine)neodymium(III), monoclinic, space group P21 / c, a 14-206(4), b 8.619(2), c 15.190(7) �, β 107.38(2)�, Z 4, R 0.035 and R, 0.039 for 2677 'observed' reflections have been determined. Both compounds have pseudotetrahedral geometry with a coordination number of 10 for the lanthanoid metal but there is a difference in the coordination of pyridine and in unit cell packing between the two structures.

NTO Polymorphs

1992 ◽  
Vol 296 ◽  
Author(s):  
Kien-yin Lee ◽  
Richard Giloxdi
Keyword(s):  
Crystal Structure ◽  
Cell Density ◽  
Unit Cell ◽  
Monoclinic Space Group ◽  
Triclinic Space Group ◽  
Space Group ◽  
Monoclinic Form ◽  
Network Of Hydrogen Bonds ◽  
Air Bag ◽  
Ray Methods

AbstractNTO is an explosive of current interest. It has been evaluated as an insensitive component to replace RDX in the bomb fill, and as a major ingredient for the auto air bag system. The crystal structure of the β from of NTO has been determined by single-crystal X-ray methods. The unit cell is monoclinic, space group P21/c, with a = 9.326, b = 5.515, c = 9.107 Å, β = 100.77°. There are four molecules in the cell, density 1.878 g/cm3. Infinite extension of H-bonding in two-dimensional sheets occurs in the monoclinic form. Bond lengths and angles all have normal values.Efforts have been made to determine the crystal structure of α-NTO. However, a structure refined only to R = 17% was obtained, probably due to some kind of twinning about the crystal needle axis. The unit cell is triclinic, space group P1, with a = 5.12, b = 10.30, c = 17.9 Å, α = 106.7°, β= 97.7°, γ = 90.2°. There are eight molecules in the cell, density 1.92 g/cm3. Ribbons of NTO molecules formed by a relatively strong network of hydrogen bonds are observed. It was found that α-NTO is the stable, dominating form. A variety of techniques have been chosen to identify the two polymorphs.

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