Structure ofp-tetrakis-(4-nitrophenylazo)calix[4]-arene-4-picoline (1∶4) complex

The structure of thep-tetrakis-(4-nitrophenylazo)calix[4]arene-4-picoline (14) complex has been determined by X-ray crystallography. Crystals are monoclinic, space groupC2/c,a=24.9097) Å,b=8.425(6) Å,c=33.81(1) Å, =101.13(2)°,D _c =1.330 g/cm³,Z=4, finalR value =0.067. The cone conformation adopted by this azocalixarene is disturbed by the positions of the picoline molecules. Two of them are inside the macorocycle cavity and the two others are outside. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. Sup. 82190 (32 pages).     

Air stable liquid clathrates: Solid state structure and hydrocarbon solubility of organic cation triiodide salts

A series of air and water stable organic cation triiodide salts have been prepared and characterized. Almost all of the salts isolated sustain liquid clathrate phases in the presence of benzene or toluene, the compositions of which were determined via¹H NMR spectroscopy. Two of the salts were also characterized via X-ray crystallography in order to determine the nature of any solid state interionic interactions (1-ethylpyridinium triiodide, monoclinic,P2₁/c,a = 9.6031(7),b = 15.129(3),c = 8.8160(16) Å, = 104.192(11)°,Z = 4,R = 0.041 for 2463 independent observed reflections; 1,2,4-trimethylpyridinium triiodide, orthorhombic,Pbcm,a = 9.434(4), 20.176(4), 7.411(4) Å,Z = 4,R = 0.045 for 966 observed reflections).     

Thiocalix[4] arenes. I. Synthesis and structure of ethylthiocalix[4]arene methyl ether and the related structure of bromocalix[4]arene methyl ether

Bromocalix[4]arene methyl ether serves as a precursor in the synthesis of the title thiocalixarene via the reagent CuSEt. Ethylthiocalix[4]arene methyl ether crystallizes in the monoclinic space groupP2₁/c witha = 20.577(9),b, = 10.722(5),c = 20.315(9) Å, = 120.46(4)°, andD _c = 1.24 g cm^–3 forZ = 4. Refinement based on 1441 observed reflections led toR = 0.080. The configuration of the calixarene lies between the partial cone and the 1,3-altemate conformations. Bromocalix[4]arene methyl ether crystallizes in the triclinic space groupPI witha = 12.283(7),b = 17.658(9),c = 18.118(6) Å, = 90.25(6), = 105.95(4), = 105.11(6)°, andD _c = 1.68 g cm^–3 forZ = 4. Refinement based on 3028 observed reflections led toR = 0.083. The unit cell also contains four CHCl₃ molecules which exist pairwise enclathrated by six calixarenes. The partial cone conformation of the bromocalixarene is identical to that of ethylthiocalix[4]arene methyl ether.     

Inclusion complexes of the natural product gossypol. Clathrate type inclusion complexes of gossypol with carbonyl group containing guests

The crystal structures of 2:1 inclusion complexes of gossypol with methyl propionate (GPMEP) and ethyl acetoacetate (GPEAA) have been determined by X-ray structure analysis. The crystals of GPMEP, C₃₀H₃₀O₈l/2 C₄H₈O₂, are monoclinic, space groupC2/c,a=11.079(3),b = 30.724(7), c = 16.515(5) Å, = 90.46(2)°,V = 5621(3) Å,Z = 8,D _x = 1.33 g cm^–3. The structure has been refined to the finalR value of 0.059 for 1899 observed reflections. The crystals of GPEAA, C₃₀H₃₀O₈l/2 C₆H₁₀O₃, are monoclinic, space groupC2/c,a=11.095(2),b=30.604(9),c = 16.955(5) Å, = 88.27(2)°,V = 5754(3) Å,Z = 8,D _x = 1.35 g cm^–3. The structure has been refined to the finalR value of 0.056 for 2502 observed reflections.In contrast to previously investigated inclusion complexes of gossypol the host molecules do not form centrosymmetric dimersvia hydrogen bonds. In the crystal structures the racemic gossypol is separated into enantiomers forming alternating bimolecular layers. Nearly perpendicular to these chiral bilayers run elongated cavities enclosed on each side by layers of opposite chirality. The surface of these layers is hydrophobic, the polar groups are hidden inside the layer. Guest molecules which are hydrogen bonded to the host are included in cylindrically shaped cavities. Possible hydrogen bonds between host and guest are analysed for this isostructural class of complexes.     

Novel butterfly tungsten-osmium carbido cluster Complexes from the reaction of Os3(CO)10(NCME)2 CPW(CO)3(CH2SMe)

Condensation of be triosmium acetonitrile complex Os₃(CO)₁₀(NCMe)₂ with the sulfido complex CpW(CO)₃(CH₂SMe) in refluxing THF solution produced three sulfur-containing compounds Os₃(C0)₁₀)(µ-H)(µ-SMe) (1), Os₃(CO)₁₁ [S(Me)CH₂W(CO)₃Cp] (2) and CpWOs₃(CO)₁₂(µ-CH₂)(µ-SMe) (3). Clusters 2 and 3 were products involving a 1:1 combination of starting materials and were characterized by X-ray diffraction studies. Crystals of 2 belongs to monoclinic space group P 2₁ /c witha=8.418(2),b = 11.912(2),c = 28.288 Å,=97.64(2)°,Z=4;R _F=0.044,R _W,=0.044. Crystal dara far 3: space group P 2₁/e,a 18.156(4).b=9.255(6),c = 15.347(4) Å. = 103.49(2)°,Z = 4;R _F -=0.047,R _W = 0.045. Upon thermolysis in toluene, the methylene cluster 3 released CO and induced C-H bond activation to afford two tetrametallic carbido clusters with formula CPWOS₃(CO)₉(µ₄-C)(µ-H)₂(µ-SMe) (4) and CPWOs₃(CO)₁₁(µ₄-C)(µ-SMe) (5) as the principle products. The first complex possesses a butterfly framework encapsulating a µ₄-C ligmd and a µ-SMe ligand linking a W-Os edge, whereas the second product adopts a puckered, cyclic arrangement of WOs₃ metal atoms with µ-SMe ligand located on a nonbonding Os-Os vector. Complex4 crystallizes in monoclinic space group P 2₁ /c witha=15.633(4) Å,b = 8.699 (3) Å,c=15.422(4) Å,=93.12(2)=°, Z=4,R=0.036,R _W =0.034 for 2780 observed reflections. Crystal data for5: space groupP nma,a=14.542(3),b=13.710(6),c=11.758(3) Å.Z=4,R _F =0.038,R _W = 0.037 for 1826 observed reflections. A variable temperature¹H NMR study was also presented to demonstrate the solution fluxionality of5.     

Inclusion complexes of the natural product gossypol. Crystal structures of gossypol complexes with benzene and chloroform as guests

The crystal structures of the lattice inclusion complexes of gossypol with benzene and chloroform have been determined by X-ray structure analysis. The crystals of (C₃₀H₃₀O₈)₂ · C₆H₆ (GPBNZ) are triclinic, space groupPI,a = 11.241(3),b = 14.986(4),c = 17.380(4) Å, = 98.89(2), = 99.86(2), = 98.91(2)°,V = 2800(2) ų,Z = 2,D _x = 1.32 g cm^–3, (CuK ) = 7.35 cm^–1. The structure has been refined to a finalR value of 0.050 for 6146 observed reflections. The crystals of C₃₀H₃₀O₈·CHCl₃ (GPCLF) are monoclinic, space groupC2/c,a = 28.464(4),b = 8.948(1),c = 26.480(4) Å, = 108.93(2)°,V = 6380(2) ų,Z = 8,D _x = 1.33 g cm^–3, (CuK) = 30.42 cm^–1. The structure has been refined to a finalR value of 0.100 for 1980 observed reflections.GPCLF forms an intercalate-type structure and GPBNZ a clathrate-type structure. There are, however, some similarities in the packing mode of the host molecules in these two structures. On a basis of comparison of the crystal packing of GPCLF and GPBNZ one can postulate that in the desorption process of the intercalate-type GPCLF complex an intermediate clathrate structure of the GPBNZ-type should be formed.     

Crystal and molecular structures of benzophenone phenylhydrazone derivatives with anticancer activity

The X-ray crystal structures of 4,4-dihydroxybenzophenone-2,4-dinitrophenylhydrazone (I) and 2,2-dihydroxybenzophenone-2,4-dinitrophenylhydrazone (II) have been determined in order to study the structural characteristics of these molecules that may contribute to their antiestrogenic and cytotoxic properties. These structures have been compared to other hydrazone derivatives as well as tamoxifen, an antiestrogen drug presently used clinically for the treatment of breast cancer.Crystal data: (I) C₁₉H₁₄N₄O₆ · C₄H₁₀O; MW=468.0; monoclinic,P2₁;a=8.601(2), b=15.502(8), c=16.851(4) Å,=98.58(2)°;Z=8; finalR=0.036 for 1904 observed reflections. (II C₁₉H₁₄N₄O₆ · H₂O; MW=410.0; monoclinic,P2₁/c;a=7.603(2),b=19.552(4),c=12.493(3) Å,=92.11(1)°;Z=4; finalR=0.045 for 1171 observed reflections.     

Complexation with hydroxy host compounds,part 5. Structures and thermal analyses of 1,2,3,4,5-pentaphenylcyclopenta-2,4-dien-1-ol and its inclusion compounds with water and dimethylsulphoxide

The crystal and molecular structures of the title host compound (I), C₃₅H₂₆O, and its inclusion complexes with water (II), C₃₅H₂₆O·H₂O and dimethylsulphoxide (III), C₃₅H₂₆O·C₂H₆OS are reported. (I) is monoclinicC2/c,a = 9.725(1),b = 20.031(3),c = 26.545(3) Å, = 90.60(1)⁰,V = 5170 ų,Z = 8; (II) is triclinic, ,a = 10.206(1),b = 10.324(2),c = 14.425(2) Å, = 101.68(1), = 89.92(2), = 116.34(1)⁰,V = 1327 ų,Z = 2; (III) is monoclinicP2₁/n,a = 17.832(5),b = 10.109(3),c = 17.901(5) Å, = 111.93(2)⁰,V = 2993 ų,Z =4. The structures were solved by direct methods and refined to final residuals of 0.045, 0.048, and 0.071, respectively. Thermal analysis of the complexes corroborates the crystallographic results.     

Formation of isolated guest dimers vs. host-guest coordination. X-Ray crystal structures of four carboxylic acid inclusion compounds formed by roof-shaped and scissor-like host molecules

The crystal structures of the inclusion compounds oftrans-9,10-dihydro-9,10-ethano-anthracene-11,12-dicarboxylic acid host (1) with formic acid (1a), acetic acid (1b), and propionic acid (1c) as guests, and of the coordinatoclathrate of the 1,1-binaphthyl-2,2-dicarboxylic acid host (2) with acetic acid as guest (2b) have been studied by single crystal X-ray diffraction. These studies show that inclusion of small carboxylic acids by carboxylic acid hosts like1 and2 results in formation of isolated, hydrogen-bonded guest dimers. Additional H-bond contacts between host and guest carboxylic groups are only formed in cases1a and2b. The dimeric acidic guest units are sitting in the cavities of the host or host-guest framework and have no other interactions than those of a weak Van der Waals' type with the neighbouring molecules. Crystal data:1·formic acid (1:2): triclinic (P),a = 11.6769(6),b = 9.4067(4),c = 9.0020(4) Å,a = 81.522(4), = 100.310(6), = 104.208(6)°,Z = 2,R = 0.048 for 2392 reflections;1·acetic acid (1:1): monoclinic (P2₁/n),a = 9.717(2),b = 14.462(2),c = 13.038(3)Å, = 104.27(1)°,Z=4,R=0.046 for 3042 observations;1·propionic acid (1:1): monoclinic (P2₁/n),a = 9.897(4),b = 14.671(7),c = 13.284(7) Å, = 105.92(6)°,Z = 4,R = 0.056 for 2302 reflections;2·acetic acid (2:3): triclinic (P),a = 12.746(1),b = 17.781(2),c = 11.010(1) Å, = 105.606(4), = 112.992(8), = 81.175(6)°,Z = 2,R = 0.067 for 4375 observations.     

Inclusion complexes of the natural product gossypol. Recognition by gossypol of halogeno methanes. Structure of the dichloromethane complex of gossypol and single crystal conservation after decomposition

The structures of gossypol complexes are extremely sensitive to the halogenomethane present as the guest; e.g. changing the number of Cl atoms in chloromethane derivatives changes the structure of the gossypol complex. The crystals of C₃₀H₃₀O₈·CH₂Cl₂ are monoclinic, space groupC2/c,a=21.320(4),b=19.199(6),c=15.765(2)Å, =113.05(2)^o,V=5916(2)ų,Z=8,D _x=1.35 g/cm³,T=295 K. The structure has been solved by direct methods and refined to the finalR value of 0.084 for 1828 reflections. In the structure H-bonded gossypol molecules form columns, generating channels in the structure which are filled by guest molecules. After decomposition (desolvation) monocrystals of the complexes are conserved without destruction, in which there are rather wide and empty channels though slightly smaller than in the complex. An attempt is made to explain some peculiarities of the behavior of the gossypol polymorph formed on the basis of its structure with empty channels. Supplementary data relevant to this article have been deposited with the British Library Publication No. SUP 82165 (17 pages).     

Structural researches on the chelating behaviour of the biguanide ligand. The crystal structures of Co(C2H6N5)3 · 2H2O and Cu(C2H7N5)2CO3·4H20

Summary Crystals of the title compounds are both monoclinic, with unit cell dimensions:a = 9.293(5),b = 10.122(5),c = 16.737(7) Å. = 103.44(3)°,Z = 4, space groupP2₁/c for the cobalt derivative;a = 13.1ß5(7),b = 17.546(ß),c = 6.871(3) Å, = 107.01(4)°Z = 4, space groupP2₁/n for the copper derivative. The structures were solved from diffractometer data by the heavy-atom technique for the first compound and by direct methods for the second compound. Refinement by block diagonal least-squares gaveR = 5.9% for 3511 independent reflections andR = 8.8% for 2885 independent reflections for the cobalt and copper compound respectively. In both compounds the biguanide moiety behaves as a bidentate chelating ligand in a symmetrical tautomeric form, but it is deprotonated in the octahedral cobalt compound and neutral in the square planar copper compound.     

Analysis of atomic displacement parameters and molecular motion in crystals. Part 2. X-ray crystal structure of K2Ru(SO4)2 * 6H2O at 160 K and 295 K

Atomic displacement parameters determined from a single-crystal X-ray-diffraction study on K₂Ru(SO₄)₂ * 6H₂O are analyzed in the molecular mean field approximation. The motion of SO₂ ^2– can be described with a rigid-body model, whereas for [Ru(H₂O)₆]²⁺ internal stretching motion and coupling between stretching motion and overall translation are found to be necessary for explaining the observed atomic displacement parameters. Frequencies and force constants of internal motion are not significantly affected by such couplings. K₂Ru(SO₄)₂ * 6H₂O crystallizes in the monoclinic space groupP2₁/c (No. 14), witha = 6.1211(7)Å,b = 12.226(2) Å,c = 8.916(2)Å, = 105.11(1)°,Z = 2 at 160 K anda = 6.1402(7)Å,b = 12.274(2)Å,c = 8.957(1)Å, = 105.25(1)°,Z = 2 at 295 K. The structure was refined to a finalR(F) of 0.017 at 160 K and of 0.019 at 295 K for 1438 and 1299 observed reflections withF ₀ > 6(F₀) and sin / > 0.617 Å^1–.     

Acetylene as a ligand on clusters: An accurate determination of the crystal and molecular structure of (Cp)2Ni2Fe(CO)3(μ3−C2H2) and of (CP)2Ni2Fe2(CO)6(μ4−C2H2)

Abstarct The Cp)₂Ni₂Fe(CO)₃(µ₃-C₂H₂) and Cp)₂Ni₂Fe(CO)₃(µ₃-C₂H₂) (B) complexes have been synthesized and spectroscopically characterized. An accurate X-ray study and a comparison with related structures shows that the substituents of the alkyne ligands exert considerable effects on the bonding parameters.Crystal data for complex A, monoclinic space group P2₁/n,a = 8.418(1),b = 15.779(2),c = 14,493(1) Å, = 91.64(1)°,Z = 4, 2753 observed reflections,R = 0.022; crystal data for complex B, monoclinic space group C2/c,a = 16.2189(7),b = 7.445(3),c = 25.745(5) Å, = 103.74(3),Z=8, 1853 observed reflections,R = 0.051.     

Cu2O(SO4), dolerophanite: Refinement of the crystal structure,with a comparison of [O Cu(II)4] tetrahedra in inorganic compounds

The refinement of the crystal structure of Cu₂O(SO₄), dolerophanite, [a=9.370 (1) Å,b=6.319 (1) Å,c=7.639 (1) Å, =122.34 (1)°; space group C 2/m;Z=4;R=0.035] confirmed the trigonal dipyramidal coordination of one Cu(II) atom (mean distance Cu-O=2.025 Å). One O atom is tetrahedrally surrounded by four Cu(II) atoms; the mean Cu(II)-O distance of 1.918 Å compares well to [O Cu(II)₄] tetrahedra found in inorganic crystal structures.de|Die Verfeinerung der Kristallstruktur von Cu₂O(SO₄), Dolerophanit, [a=9.370 (1) Å,b=6.319 (1) Å,c=7.639 (1) Å, =122.34 (1)°; Raumgruppe C 2/m;Z=4;R=0.035] bestätigte die trigonal dipyramidale Koordination des einen Cu(II)-Atoms (mittlerer Cu-O-Abstand=2.025 Å). Ein O-Atom ist tetraedrisch von vier Cu(II)-Atomen umgeben; der mittlere Cu(II)-O-Abstand von 1.918 Å entspricht den in ähnlichen [O Cu(II)₄]-Tetraedern von anorganischen Kristallstrukturen gefundenen Werten.

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Cu₂O(SO₄), Dolerophanit: Verfeinerung der Kristallstruktur mit einem Vergleich von [O Cu(II)₄]-Tetraedern in anorganischen Verbindungen

     

Nickel complexes of 1-methylimidazoline-2(3H)-thione: crystal structures of trans-dichlorotetrakis(1-methylimidazoline-2(3H)-thione)nickel(II) and tetrakis[1-methylimidazoline-2(3H)-thione]nickel(II) tetrafluoroborate

Summary Crystal structures have been determined for two nickel complexes of the monodentate S-donating ligand 1-methyl imidazoline-2(3H)-thione (mimtH). The parainagnetic trans-octahedral complex, [Ni(mimtH)₄Cl₂], crystallises in an orthorhombic unit cell (a=12.459(1),b=13.078(1),c=15.406(1)Å, V=2510.24ų,Z=4, space group Pbca). Final conventional R from 1848 observed data [F>4(F)] is 0.0273. The Ni–Cl distance is. 2.537(1) Å and the mean Ni–S distance is 2.479 Å.The diamagnetic complex, [Ni(mimtH)₄](BF₄)₂, contains a distorted square-planar cation which is H-bonded. to [BF₄]^– anions. The complex crystallises in an orthorhombic unit cell [a=9.810(1),b=14.585(1),c=20.120(2)Å, V=2878.8ų,Z=4, space group Pbcn]. Final conventional R from 1756 observed data [F>4(F)] is 0.0629. The average Ni–S distance is 2.216Å.     

Reaction of trimethylaluminum with crown ethers. III. The synthesis and crystal structure of (12-crown-4)bis(trimethylaluminum)

The crown ether 12-crown-4 reacts with trimethylaluminum in toluene to form the complex [AlMe₃]₂[12-crown-4]. Attempts to utilize the remaining two oxygen atoms for coordination to AlMe₃ molecules were unsuccessful. The 21 complex crystallizes in the monoclinic space groupP2₁/n witha=11.342(7),b=12.941(4),c=6.973(6) Å, and =95.48(4)°. Refinement led to a finalR value of 0.047 for 925 observed reflections. The molecule resides on a crystallographic center of inversion, and as required by symmetry, the four oxygen atoms are planar. The Al–O bond is strong as revealed by the bond length of 1.977(3) Å. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82013 (9 pages).     

Hydrogen-Bonded Urea-Anion Host Lattices. Part 4. Comparative Study of Inclusion Compounds of Urea with Tetraethylammonium and Tetraethylphosphonium Chlorides

New inclusion complexes (C₂H₅)4E+Cl-2(NH2)2CO(1, E = N; 2, E = P) have beenprepared and characterized by X-ray crystallography. Crystal data, MoK radiation: 1, space group P21/c,Z = 4, a = 10.492(6), b = 14.954(8), c = 10.335(6) Å, = 91.02(5)°, R _F = 0.050 for 1527 observed data; 2, space group Pmn21, Z = 2, a = 7.446(1), b = 9.200(2), c = 12.753(3) Å, R _F = 0.079 for 519 observed data. In compound 1 the tetraethylammonium ions are sandwiched between puckered layers, which are constructed from the linkage of chloride ions and wide urea ribbons each composed of a broadside arrangement of centrosymmetric hydrogen-bonded urea dimers. In the crystal structure of 2, hydrogen-bonded urea ribbons running parallel to [100] are connected by chloride ions to generate a sawtooth wave layer, and stacked columns of tetraethylphosphonium cations are sandwiched between adjacent layers.Supplementary Data relating to this article have been deposited with the British Library as Supplementary Publication No. SUP 82216 (11 pages).     

Crystal and molecular structure of the (1 : 1) clathrate between a calix[4]arene containing onep-nitrophenol unit and toluene

p-(Methyl,tert-butyl, nitro,tert-butyl) calix[4]arene: toluene, C₃₇H₄₁NO₆. C₇H₈,M _r = 687.87, triclinic, ,a = 13.668(2),b = 12.187(2),c = 13.231(1) Å, = 106.78(8), = 77.88(1), = 114.00(1)°,V = 1916.8(8) ų,Z = 2,D _x = 1.19 g cm^–3, (CuK ) = 1.54178 Å, = 5.90 cm^–1,F(000) = 736,T = 293 K, finalR = 0.068 for 6309 observed reflections. This macrocycle, having different substituents at the positionspara to the hydroxyl groups, is the first one of its type to be studied. The general conformation of this calix[4]arene is compared to similar symmetrical ones. Thetert-butyl groups are not disordered as is usual and toluene is retained between the macrocycles. Two calixarene molecules are positioned to permit atert-butyl group of one to be inside the cavity of the second to establish CH₃- interactions.     

The W2Cl4(NHCMe3)2(PR 3)2 molecules (R 3=Me3, Et3, Pr n 3, Me2Ph) I. Their isomeric forms,interconversion proeesses,crystalline forms,and detailed molecular structures

A thorough study of compounds with the formula W₂Cl₄(NHCMe₃)2(PR₃)₂, withR ₃=Me₃, Et₃, Prg ⁿ ₃ Me₂,Ph, is reported. In addition to the previously reported crystalline compounds, namely Ia,trans-W₂Cl₄(NHCMe₃)₂(PMe₃)₂ in space group Pmmn;3a,trans-W₂Cl₄(NHCM₃)₂(PEt₃)₂ in space group P2₁/^a (or P2₁/^c); and4,cis-W₂Cl₄(NHCMe₃)₂(PMe₂Ph)₂ in Pna2₁, we have obtained and structurally characterized the following new substances,1b,trans-W₂Cl₄,(NHCMe₃)₂(PMe₂)₂, space group P2₁/^c,a= 12.233 (4) Å,b= 12.872 (4) Å,c=17.095 (5) Å,=93.52 (2)°,Z=4,V=2687 (1) ų 2,cis-W₂Cl₄(NHCMe₃)₂(PMe₃)₂, P2₁/^c,a=9.673 (4) Å,b=17.249 (4) Å,c=16.244 (5) Å,=99.63 (3),Z = 4 ,V=2669 (1) Å.3b,trans-W₂Cl₄(NHCMe₃)₂(PEt₃)₂, Pl,a=16.850 (3) Å,b=17.797 (3) Å,c= 11.459 (2)Å,= 101.02 (1),= 103.13°, y=84.23 (1)°,Z=4,V= 3279 (1) Å5,trans-W₂Cl₄(NHCM₃)₂(PMe₂Ph)₂, Fdd2,a=39.563 (8) Å at 20°C; 39.325 (10) Å at -6O°C,b = 57.543 (17) Å at 20°C; 57.186 (16) Å at -60°C,c= 8.810 (1) Å at 20°C; 8.770 (1) Å at - 60°C ,Z=24,V=20057 (7) ų (20°C), 19723 (8) ų ( - 60°C) .6,trans-W₂Cl₄(NHCMe_{3 2}(PPrⁿ ₃)₂, Pl,a= 17.287 (2) Å (20°C); 17.077 (5) Å (-60°C),b= 19.119 (2) Å (20°C); 18.952 (6) Å (-60°C),c= 12.713 (1) Å (20°C); 12.668 (4) Å (-60°C),Z=4,V= 3980 (1) ų (20°C), 3898 (2) ,ų ( - 60°C). In addition, the structure of3a was re-determined and refined so that the disorder ratio was a refined parameter, leading to a value of 0.520:0.480 instead of being arbitrarily fixed at 0.50:0.50. In all of the structures the molecules are held in eclipsed (but very distorted) rotational conformations and the W-W distances are all within the range of 2.305-2.330 Å. As will be shown in a later paper, for all phosphines, thecis andtrans isomers are of similar stability and an equilibrium mixture exists in solution. It is also shown that1a and3a do not contain unexpectedly short W-N bonds as previously reported.     

Crystal structure of supramolecular complexes formed by 18-crown-6 andcis-anti-cis-dicyclohexano-18-crown-6 (host) with 3,4-diaminofurazane (guest)

An X-ray—diffraction study is reported for two molecular complexes containing 3,4-diamino-1,2,5-oxadiazole as guest (G) with 18-crown-6 (18-C-6) andcis-anti-cis-dicyclohexano-18-crown-6 (DCH-6B) as host. Both complexes are of the polymeric-chain structure with the guest molecule bridging two crown neighbours. ComplexI: [18-C-6*G*H₂O], 111, monoclinic,P2₁/n,a=8.171(1),b=15.042(2),c=16.209(6) Å, =101.15(2)°, finalR-factor 0.068. ComplexII: [DCH-6B*G], 11, monoclinicC2/c,a=21.212(4),b=9.380(2),c=13.049(3) Å, =108.61(3)°, finalR 0.047.