Cell Parametersa Research Articles

Structure Determination of Two Polymorphic Phases of La(NO3)3· 4H2O from X-Ray Powder Diffraction

The structure of two polymorphic phases of lanthanum nitrate tetrahydrate, prepared from the thermal decomposition of the hexahydrate compound, have been determined from conventional monochromatic X-ray powder diffraction data. The α phase has a monoclinic unit cell with the parametersa= 6.7778(9) Å,b= 11.3673(1) Å,c= 6.5843(1) Å, β = 90.644(5)°, space groupP21/m. The β phase is orthorhombic with the unit cell parametersa= 11.834(1) Å,b= 12.973(1) Å,c= 13.531(1) Å, space groupPbca. For the α phase, atomic coordinates were found by interpretation of one Patterson and three difference Fourier maps, while for the β phase the starting model was the crystal structure of the related cerium compound. The structure models were refined by the Rietveld method. The structures consist of infinite chains along [001], built from 11-fold coordinated and 10-fold coordinated La atoms in the α and β phases, respectively, and linked by bridging nitrate groups. The cohesion of the structures is ensured by hydrogen bonds.

Crystal structures of 4,11-pregnadiene-3,20-dione and 21-methyl-20-oxa-4-pregnene-3,20-dione

The structures of the title compounds were solved by direct methods and refined by anisotropic full-matrix least-squares methods. 4,11-Pregnadiene-3,20-dione, C21H28O2(1) crystallizes in the monoclinic space groupP21 (Z=2). The unit cell parametersa, b, c (A), and β (°) were: 12.319(2), 7.700(2), 9.717(2), 109.41(2). TheA- andC-rings exhibit intermediate sofa-halfchair conformations. TheB-ring has a chair conformation and theD-ring assumes an intermediate envelope-half-chair conformation. The progesterone side chain has a typical conformation; the C16−C17−C20−O20 torsion angle is −15.1(4)°. 21-Methyl-20-oxa-4-pregnene-3,20-dione, C21H30O3 (2) crystallizes in the orthorhombic space groupP212121 (Z=4). The unit cell parametersa, b, c (A) were: 12.926(2), 19.447(4), 7.313(1). The progesterone side chain has an unusual conformation; the C16−C17−C20−O20 torsion angle is 174.6(4)°. TheA-ring has a 1α, 2β-half-chair conformation, ringsB andC exhibit chair conformations and ringD is in a 13β,14α-half-chair conformation.

Crystal structure of (diphenyl)(morpholino)phosphiniminocyclotrithiazene

The title compound (C6H5)2(OC4H8N)P=N−S3N3 crystallizes in the space group\(P\bar 1\) with unit cell parametersa=9.3900(2),b=9.4747(1),c=11.3850(3) A, α=95.73(4), β=96.85(6), γ=104.26(2)o, and Z=2. The tricoordinated sulfur of the cyclotrithiazene ring deviates from the mean plane of other skeletal atoms by 0.683(4) A. The angle at this atom is the smallest in the ring and is enclosed by the longest S−N bonds observed in the ring.

Crystal Structure of Orthorhombic LT-Na2TiSiO5and Its Relation to the Tetragonal HT-Form

Na2TiSiO5is trimorphous. Single crystals of the low temperature modification have been obtained by a flux method (V2O5/MoO3). The crystal structure of LT-Na2TiSiO5represents a new structure type with a hitherto unknown three-dimensional net of TiO5square pyramids and SiO4tetrahedra. LT-Na2TiSiO5crystallizes in the orthorhombic space groupPmc21with unit cell parametersa= 9.1814(3) Å,b= 4.8075(2) Å,c= 9.8604(4) Å,Z= 4. Chains oftrans-connected TiO6octahedra are linked by corners of SiO4tetrahedra. The octahedra are distorted to square pyramids with five short (1 × 1.70 Å, 4 × 1.97 Å) and one long (3.11 Å resp. 3.48 Å) Ti–O distances. There are two different chains with parallel and antiparallel orientation of the short Ti–O bonds leading to a polar structure. Single crystals are frequently twinned because of a phase transition at 772°C. A structure model for the tetragonal HT-form is proposed and its relation to the LT-form discussed. Because of special structural features LT-Na2TiSiO5is interesting as a new nonlinear optical material.

Synthesis, Crystal Structure, and Physical Properties of a New Reduced Lanthanum Niobium Oxide: LaNb7O12

Single crystals of LaNb7O12were obtained by annealing a mixture of La2O3, Nb2O5, and Nb in 1:1:1 molar ratio with NH4Cl in a sealed quartz tube. LaNb7O12crystallizes in the monoclinic space groupP21/cwith cell parametersa= 10.762(1),b= 9.192(1),c= 10.314(1) Å, β = 104.25°, andz= 4 formula units per cell. The structure was determined from single-crystal X-ray diffraction data and refined to a residual ofR(F) = 0.037 andRw(F2) = 0.077 for 119 variable parameters and a unique data set of 1400 observations [I> 2σ(I)]. The essential building units of the structure are Nb6and NbO6octahedra and La ions in eight coordination of oxygen. Two NbO6octahedra corner-share to form a pair and connect with Nb6octahedra via oxygen atoms. Nb6octahedra share both apical and inner oxygen atoms with neighboring Nb6to form columns of Nb6O12clusters along thecaxis. The Nb6O12clusters exhibit 14 valence electrons inM–Mbonding states. LaNb7O12is a semiconductor with an activation energy of 0.08 eV. The magnetic susceptibility data show weak temperature-independent paramagnetism. The Madelung part of the lattice energy has been calculated and is discussed.

Crystal Structure of Te2O3F2

Te2O3F2crystallizes with the triclinic symmetry (space groupP-1) and the unit cell parametersa= 515.3(1) pm,b= 625.7(1) pm,c= 688.8(1) pm, α = 98.71(1)°, β = 110.31(1)°, γ = 92.72(1)°,Z= 2. Its structure was solved and refined toRvaluesR1= 0.024 and wR2= 0.059 on the basis of 699 independent reflections recorded on a single crystal with an automatic four-circle diffractometer. The two Te atoms are, respectively, fourfold and fivefold coordinated and their lone pairEis stereochemically active. The bond valence calculation shows a perfect O/F order. The Te(1)O3FEand Te(2)O4FEpolyhedra form, by sharing O–O edges, bipolyhedral units with a very short Te–Te distance (319 pm). These units, by sharing corners, constitute independent sheets parallel tox0y. All the F atoms are nonbridging and orientated, together with the lone pairsE, toward the interlayer space. The structural relationships with the α-TeO2structure have been evidenced and analyzed.

Purification, Crystallization, and Preliminary X-Ray Diffraction Analysis of the Carbapenem-Hydrolyzing Class A β-Lactamase Sme-1 fromSerratia marcescens

The carbapenem-hydrolyzing class A β-lactamase Sme-1 fromSerratia marcescensS6 was expressed inEscherichia coliand purified by ion-exchange chromatography and gel filtration. Crystals of the purified enzyme were obtained by the hanging drop vapor diffusion method using polyethylene glycol 4000 as precipitant. The crystals belong to the monoclinic space group P21with unit cell parametersa= 81.48 Å,b= 51.76 Å,c= 71.81 Å, α = γ = 90°, and β = 118.71°. There are two monomers in the asymmetric unit and the calculated Matthew's volume is 2.26 Å3/Da. The crystals, which diffract to at least 2.3 Å resolution, are suitable for X-ray structure analysis.

Triosmium clusters derived from the reactions of thioureas with dodecacarbonyltriosmium: Crystal structures of [Os3(CO)11{η 1-SC(NMe2)2}], [Os3(CO)9(μ-OH)(μ-OMeOCO){η 1-SC(NMe2)2}] and [(μ-H)Os3(CO)9{μ 3-NHC(S)NH2}

The reaction of [Os3(CO)12] with tetramethylthiourea in the presence of a methanolic solution of Me3NO·2H2O at 60° yields the compounds [Os3(CO)11{η1-SC(NMe2)2}] (1) in 56% yield and [Os3(CO)9(μ-OH)(μ-MeOCO){η1-SC(NMe2)2}] (2) in 10% yield in which the tetramethylthiourea ligand is coordinatedvia the sulfur atom at an equatorial position. Compound2 is a 50 e− cluster with two metal-metal bonds and the hydroxy and methoxycarbonyl ligands bridging the open metal-metal edge. In contrast, the analogous reaction of [Os3(CO)12] with thiourea gives the compounts [(μ-H)Os3(CO)10{μ-NHC(S)NH2}] (3) in 8% yield and [(μ-H)Os3(CO)9{3-NHC(S)NH2}] (4) in 30% yield. In3, the thioureato ligand bridges two osmium atomsvia the sulfur atom, whereas in4 in addition to the sulfur bridge, one of the nitrogen atoms of thioureato moiety bonds to the remaining osmium atom. The decacarbonyl compounds 3 can also be obtained in 50% yield from the reaction of [Os3(CO)10(MeCN)2] with thiourea at ambient temperature. Compound3 converts to4 (65%) photochemically. Compound1 reacts with PPh3 and acetonitrile at ambient temperature to give the simple substitution products [Os3(CO)11(PPh3)] and [Os3(CO)11(MeCN)], respectively, while with pyridine, the oxidative addition product [(μ-H)Os3(CO)10(μ-NC5H4] is formed at 80°C. All the new compounds are characterized by IR,1-H-NMR and elemental analysis together with the X-ray crystal structures of1,2 and4. Compound1 crystallizes in the triclinic space group P\(P\bar 1\)with unit cell parametersa = 8.626(3) A,b = 11.639(3) A,c = 12.568(3_ A,α = 84.67(2)°,β = 75.36(2)°,γ = 79.49(3)°,V = 1199(1) A3, andZ = 2. Least-squares refinement of 4585 reflections gave a final agreement factor ofR = 0.0766 (R w = 0.0823). Compound2 crystallizes in the monoclinic space group P21/n with unit cell parametersa = 9.149(5) A,b = 17.483(5) A,c = 15.094(4) A,β = 91.75(2)°,V = 2413(2) A3, andZ = 4. Least-squares refinement of 3632 reflections gave a final agreement factor ofR = 0.0603 (R w = 0.0802). Compound4 crystallizes in the monoclinic space group C2/c with unit cell parametersa = 13.915(7) A,b = 14.718(6) A,c = 17.109(6) A,β = 100.44(3)°,V = 3446(5) A3, andZ = 8. Least-squares refinement of 2910 reflections gave a final agreement factor ofR = 0.0763 (R w = 0.0863).

Untersuchungen des Hydroxylammonium-Fluorogallats

Crystals of (NH3OH)3GaF6 have been isolated from aqueous solution. The compound crystallizes triclinic, with cell parametersa=6.539(5) A,b=6.924(5) A,c=9.403(1) A, α=87.01(9)°, β=83.98(8)°, γ=70.28(8)°. The thermal decomposition was studied by TG and DSC analysis.

NaH[Cu2(O2C2H3)6]: A New Compound Containing Copper-to-Copper Bonding

While attempting the synthesis of the mineral diabolite Pb2CuCl2(OH)4via a gel growth method, a new and interesting copper compound was isolated. The slow crystal growth of this new blue compound was generated from silica gel acidified with acetic acid. The crystals grew in the gel for over a period of one year. Attempted characterization using the X-ray powder technique indicated the crystals to be a new phase and not that of the mineral diabolite. Single-crystal studies were carried out and a new structure was obtained. The structure is based on square pyramidal complexes of copper in which the two pyramids interact through Cu–Cu bonds. Its chemical composition was deduced to be NaH[Cu2(O2C2H3)6]. The structure is similar to that found in the classical copper acetate dimer which possesses unusual magnetic properties. Its synthesis, chemical characterization, and structure is described. The space group for this new copper dimer isI2/a,Z= 4, with unit cell parametersa= 8.145(2) Å,b= 17.828(3) Å,c= 13.531(2) Å, and β = 98.70(2)°.

Synthesis and reactivity of $$(\mu - H)(\mu _3 - \eta ^2 - H_2 )_4 )Os_3 (CO)_9 $$ : An unusually reactive triosmium cluster

The synthesis of\((\mu - H)(\mu - \eta ^2 - H_2 )_4 )Os_3 (CO)_{10} \) (4) from piperidine and Os3(CO)10(CH3CN)2 and its solid state structure are reported. The room temperature reactions of the decarbonylation product of4,\((\mu - H)(\mu _3 - \eta ^2 - H_2 )_4 )Os_3 (CO)_9 \) (3), with P(C6H5)3, CNCH3, HCl and H2 are reported. Overall, the products obtained closely resemble those obtained from the analogous,\((\mu - H)(\mu _3 - \eta ^2 - H_2 )_3 )Os_3 (CO)_9 \) (1). The isomerizations of the phosphine addition products\((\mu - H)(\mu - \eta ^2 - H_2 )_n )Os_3 (CO)_9 P(C_6 H_5 )_3 \) (n = 3,6a;n = 4,5a) have been studied by1H-NMR techniques and the initial rearrangement was shown to be an intramolecular process. Slower conversion to the complex\((\mu - H)(\mu _3 - \eta ^2 - H_2 )_4 )Os_3 (CO)_8 P(C_6 H_5 )_3 \) (8) was observed and the solid state structure of this product is reported and compared with a related compound containing an ethyl,n-propylμ3-imidoyl ligand. Compound4 crystallizes in the triclinic space group Pl (#2) withZ= 2, and unit cell parametersa = 9.294(3) A,b = 15.758(5) A,c = 7.406(2) A,a = 81.10(2)°,β=76.47(2)°,y =74.88(2)°, andV =1013(l) A3. Least-squares refinement of 2677 reflections gave a final discrepancy factor ofR = 0.054 (R w = 0.066). Compound8 crystallizes in the space group C2/c with unit cell parametersa = 24.818(3) A,b = 16.389(3) A,c = 18.111(3) A,β= 120.94(2)°,V = 6318(4) A3, andZ = 8. Least squares refinement of 3439 reflections gave a final discrepancy factor ofR = 0.039 (R w =0.047).

Crystal structures of 2-phenyl- and 2-benzyl-5,6-dihydro-6-hydroxy-7H-1,2,4-triazolo [3,2-b] 1,3-thiazines

The examined compounds crystallize in the monoclinic space groupsP2 1/c (phenyl derivative,1) andP2 1/a (benzyl derivative,2). The unit cell parametersa, b, c (A) and β (°) were: 6.402(1), 16.506(1), 10.144(1), 97.48(1) for1 and 12.099(2), 4.612(1), 21.712(4) and 105.20(2) for2. The finalR(Rw) factors were 0.043 (0.041) and 0.121 (0.126) for1 and2, respectively. Both molecules have similar geometry of the bicyclic system with flat 1,2,4-triazole rings, sofa conformations of 1,3-thiazole ones and axial hydroxy groups. In the crystals the molecules form infinite chains (by means of O−H...N(4) hydrogen bonds), enantiomeric in1 and racemic in2.

Electron density maps of lysozyme calculated using synchrotron laue data comprising singles and deconvoluted multiples

We have used lysozyme as a test case to illustrate the application of a new method of estimating the intensities of Laue multiples reflection data in protein crystallography. Hen egg-white lysozyme, an enzyme with a single polypeptide chain of 129 amino acids, crystallizes in space group P43212 with cell parametersa=b=79·1 Å,c=37·9 Å. Laue image plate data were collected using synchrotron radiation on station 9·5 at Daresbury with a total exposure time of 0·95 seconds. The data processed were separated into two data sets comprising the singles and the combined singles and deconvoluted multiples. The method of deconvolution was that of Campbell and Hao (1993), which utilizes the intensity variation of theλ-curve. Electron density maps (2F o−F c) based on the two data sets are then compared. This comparison shows that the deconvoluted multiples do indeed contribute usefully to the continuity of the maps due to the improved completeness of the data. A number of map sections along the polypeptide chain, based on the two Laue data sets, are shown for comparison. These include Arg 5, His 15, Phe 38, Asp 52, Tyr 53, Pro 70, Trp 108 and the four disulphide bridges.

Crystal and molecular structure of 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane: Energy and structural relationships for this tetraazamacrocycle in its neutral and protonated forms

The X-ray crystal structure of 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane has been determined. The neutral ligand crystallises in the triclinic space groupP\(\bar 1\) with unit cell parametersa=8.467(4),b=10.057(5),c=10.637(5) A, α=67.68(3), β=75.38(4), γ=76.34(4)°,V=800.75 A3 andDc=1.063 g cm−3 forZ=2.R=0.047 for 2140 unique observed (I/σ(I)≥2.0) reflections (Rw=0.052). Two crystallographically independent molecules are observed. Both are centrosymmetric and adopt a mesodentate conformation. Molecule (1) is identified as the (R, S, S, R)-[trans-IV] isomer and molecule (2) as the (R, R, S, S)-[trans-III] isomer. Molecular mechanics calculations provide a basis for understanding the structural and energetic relationships between the neutral and protonated forms of this tetraazamacrocyclic ligand.

Reaction of trimethylaluminum and trimethylgallium with bifunctional amines: Syntheses and molecular structures of [Me2Al−N(CH2CH2)2−C−(OCH2)2]2 and [Me2Ga−N(Si(H)Me2)2

The crystalline products [Me2Al−N(CH2CH2)2−C−(OCH2)2]2 (I) and [Me2Ga−N(Si(H)Me2)2]2 (II) were prepared from reactions of trimethylaluminum and trimethylgallium with 1,4-dioxa-8-azaspiro[4.5]-decane and 1,1,3,3-tetramethyldisilazane, respectively, in toluene. The organoaluminum dimer crystallizes in the monoclinic space groupP21/c with unit cell parametersa=8.970(2) A,b=9.683(2) A,c=12.833(3) A, β=103.18(2)°,V=1085.3(3) A3, andDcalcd=1.22 g cm−3 forZ=2. Least-squares refinement based on 935 observed reflectionsI>3σ(I) in the range 3.5° 3σ(I) in the range 3.5°<2ϑ<48.0° led to a finalR factor of 0.055 (R w =0.070). Both compoundsI andII reside about a crystallographic center of symmetry and contain a planar M2N2 (M=Al forI, Ga forII) four-membered ring withI having an Al...Al contact of 2.801 A.

X-ray structure and13C NMR assignments of indole alkaloids fromAspidosperma cruenta

The leaf tissue ofAspidosperma cruenta was studied for alkaloid content. Two alkaloids were isolated and shown by a combination of MS, X-ray, and high field NMR analysis to be obscurinervine and obscurinervidine. X-ray analysis of obscurinervine provided the first quantitative structural information on this compound. Obscurinervine (C25H30N2O5) crystallized in the monoclinic space groupP21 with unit cell parametersa=12.863(3)A,b=9.646(2)A,c=18.484(3)A,β=105.14(5)°,V=2213.8(8)A3,Dc=1.316 Mg/m3, andZ=4. The structure was solved by direct methods and refined toR=0.054 for 3468 observed reflections. The 2D INADEQUATE NMR experiment provided the first13C chemical shift assignments for obscurinervine. Nineteen of the 2313C-13C connections present were detected. Corresponding13C assignments for obscurinervidine were made by comparison to the spectrum of obscurinervine. The average natural concentrations of the alkaloids were determined to be 0.780% (obscurinervine) and 0.737% (obscurinervidine) by HPLC analysis. Obscurinervine was tested for antiviral and cytotoxic effects. Noin vitro activity was observed.

Crystal and molecular structure of (Z)-2-(1,3-benzothiazol-2-yl)-2-(6,7,8,9-tetrahydro-5H-benzocyclohepten-5-ylidene)ethanonitrile

The title compound C20H16N2S is crystallized in the monoclinic space groupP21/c with cell parametersa=10.663(4),b=17.585(9),c=9.418(5)A,β=115.23°(4),V=1598(3)A3,Z=4. The structure was refined by full-matrix least-squares methods using X-ray data set collected at room temperature. A finalR F =0.033 andR w =0.048 for 2225 unique reflections withI> 3σ(I) and 272 variables was obtained. The X-ray crystallographic study establishes theZ stereochemistry of the title compound.

Heteropolymetallic complexes of 1,1?-bis (diphenylphosphino)ferrocene, dppf. VIII. X-ray crystal structure of copper(I) dimer [(?-dppf)(Cu(dppf))2](ClO4)2 1

The dimeric Cu(I) complex [(μ-dppf)(Cu(dppf))2](ClO4)2, where dppf is Fe((n5-C5H4)P-(C6H5)2)2, has been characterized by single-crystal X-ray crystallography. The complex crystallizes in the triclinic space groupP1 (no. 2) with unit cell parametersa=21.852(5),b=18.063(5),c=14.867(5)A, α=114.32(3), β=109.87(3), γ=82.84(3)°. The structure was refined toR=5.40% based on 5562 observed reflections. Two crystallographically independent, structurally equivalent, units were observed in the structure. The structure consists of the centrosymmetric dimeric [(μ-dppf) (Cu(dppf))2]2+ cations and ClO4/− anions. The copper atoms are three-coordinate being trigonally bonded to one chelating and one bridging ligand. The P-Cu-P bond angles for the chelating dppf ligand are 111.1(2)° and 111.3(2)°, while the P-Cu-P angles linking different dppf molecules range from 123.9(2) to 124.2(2)°. Cu-P bond distances fall within normal ranges lying between 2.265(5) and 2.285(4)A, with the values for the chelating dppf being slightly larger than those observed for the bridging ligand. The cyclopentadienyl rings are exactly staggered and parallel, and the P atoms 180° opposed in the bridging dppf, while the rings maintain an approximately staggered configuration and are inclined by 1.6° to each other with the P atoms being 39.5° apart in the chelating ligand. A steric control of the stereochemistry of the monomer fragment of the dimer complex is suggested.

Crystal structure of 5-fluoro-1-(2,3,6-trideoxy-?-l-glycero-hex-2-enopyranos-4-ulosyl)uracil

The present compound crystallizes in the space groupP212121 withZ=4 and cell parametersa=21.687(2),b=8.155(3),c=5.883(2)A. The structure was solved by direct methods and refined by full-matrix least-squares to a finalR value of 0.045 for 1153 observed reflections. The N-glycosidic torsion angle χCN is in the anti-range and the pyranosyl ring adopts a distorted half-chair conformation with φ2=142.7(4)°,θ2=124.4(3)° andQ=0.456(2)A. In the crystal packing the molecules are linked together by N-H⋯O hydrogen bonds and C-H⋯O contacts.

Crystal structure and charge distribution for 20 oximino-5?-pregn-16-eno[3, 4,-c]-1?2?5?-oxadiazole (HS998)

The crystal structure of the modified steroid, 20 oximino-5α pregn-eno [3, 4-c] 1′2′5′ oxadiazole (HS998) using X-ray diffraction is reported. HS998 crystallizes in the orthorhombic space groupP212121, having cell parametersa=13.465(3),b=18.792(4),c=7.598(2) A;Z=4. The structure was solved by direct methods and refined by full matrix least squares toR=0.060 for 3478 reflections.