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The synthesis of a Gd-doped BaPrO 3 –BaZrO 3 solid solution has been investigated in an effort to stabilize the BaPrO 3 perovskite, a system with poor chemical stability and endurance for humid, CO 2 and reducing conditions. The phases BaZr x Pr 1− x Gd 0.3 O 3− δ ( x = 0–0.7, Δ x = 0.1) have been prepared by acrylamide combustion synthesis. The solid solution is characterized by X-ray powder diffraction, scanning electron microscope (SEM) and durability against CO 2 , moisture and reducing conditions investigated. Crystal structure parameters were obtained from X-ray powder diffraction data and results show its symmetry increases by increasing Zr content. BaZr 0.1 Pr 0.6 Gd 0.3 O 3− δ has a maximum weight increase due to reaction with CO 2 of nearly 13%, while this is reduced below 2% for BaZr 0.5 Pr 0.2 Gd 0.3 O 3− δ . The material appears to be unaltered by 5%H 2 /Ar for x ≥ 0.5, and under wet Ar for x ≥ 0.4, and thus render a higher chemical stability and confirms the stabilizing role of BaZrO 3 . However, microstructure investigations reveal gadolinium segregation due to the high doping level of the perovskite.

The crystal structure of N-α-acetyl-L-arginine-methyl ester hydrochloride has been determined from X-ray diffraction data. The crystals are orthorhombic, space group P212121, a = 15.746 (4), b = 11.569 (4), c = 7.158 (3) A, Z = 4. The structure was solved by direct methods (MULTAN) and refined by fullmatrix least-squares to an R = 0.070 for all observed reflections. The molecule shows a planar peptidic unit, with a distortion of H(N1) due to hydrogen bond interaction. The side chain is in the low energy all-trans conformation. The guanidinium group forms three hydrogen bonds with the carbonyl oxygens of two neighbouring molecules. A direct interaction of the peptidic NH with the chloride ions is observed. The latter ions also interact with the guanidinium groups, neutralizing their charges.

Four new metal complexes {M = Pd(II) or Pt(II)} containing the ligand 9-aminoacridine (9AA) were prepared. The compounds were characterized by FT-IR andH,C, andPtNMR spectroscopies. Crystal structure of the palladium complex of formulae[Pd(9AA)(μ-Cl)]2·2DMF was determined by X-ray diffraction. Two 9-acridine molecules in the imine form bind symmetrically to the metal ions in a bidentate fashion through the imine nitrogen atom and the C(1) atom of the aminoacridine closing a new five-membered ring. By reaction with phosphine or pyridine, the Cl bridges broke and compounds with general formulae [Pd(9AA)Cl(L)] (whereL=PPh3or py) were formed. A mononuclear complex of platinum of formulae [Pt(9AA)Cl(DMSO)] was also obtained by direct reaction of 9-aminoacridine and the complex [PtCl2(DMSO)2]. The capacity of the compounds to modify the secondary and tertiary structures of DNA was evaluated by means of circular dichroism and electrophoretic mobility. Both palladium and platinum compounds proved active in the modification of both the secondary and tertiary DNA structures. AFM images showed noticeable modifications of the morphology of the plasmid pBR322 DNA by the compounds probably due to the intercalation of the complexes between base pairs of the DNA molecule. Finally, the palladium complex was tested for antiproliferative activity against three different human tumor cell lines. The results suggest that the palladium complex of formula[Pd(9AA)(μ-Cl)]2has significant antiproliferative activity, although it is less active than cisplatin.

The crystal structure of monoclinic KLu(WO4)2(KLuW) crystals was determined at room temperature by using single-crystal X-ray diffraction data. The unit-cell parameters werea= 10.576 (7),b= 10.214 (7),c= 7.487 (2) Å, β = 130.68 (4)°, withZ= 4, in space groupC2/c. The unit-cell parameters of KLu1−xYbx(WO4)2were determined in relation to Yb concentration. Vickers micro-indentations were used to study the microhardness of KLuW. The linear thermal expansion tensor was determined and the principal axis with maximum thermal expansion (\alpha_{33}' = 16.72 × 10−6 K−1), X_3', was located 13.51° from thecaxis. The room-temperature optical tensor was studied in the near-infrared (NIR) and visible range. The principal optical axis with maximum refractive index (ng= 2.113),Ng, was located 18.5° from thecaxis at 632.8 nm. Undoped and ytterbium-doped KLuW crystals were grown by the TSSG (top-seeded-solution growth) slow-cooling method. The crystals show {110}, {\bar{1}11}, {010} and {310} faces that basically constitue the habit of the KLuW crystals.

The crystal structure of type III KGd(PO3)4 has been solved, and the related data are presented in this paper. KGd(PO3)4 (KGP) is monoclinic and has P21 as space group. Its cell parameters are a = 7.255(4) A, b = 8.356(5) A, c = 7.934(5) A, β = 91.68(5)°, and Z = 2. KGP is characterized by infinite polyphosphate long chains, which run along the [100] direction and are linked through gadolinium polyhedra. We determined the crystallization region of KGd0.47Nd0.53(PO3)4, and compared it to those of KGP and KNd(PO3)4 (KNP). The isotherms of the saturation temperature and four neighboring phases were also determined. Small Nd-substituted KGP single crystals free of macroscopic defects were successfully grown under conditions similar to those used to grow KGP and KNP crystals. Nd substitution on the structure was efficient, and its effect was analyzed. We determined the transparency windows of both KGP and KNP crystals, and evaluated the optical tensors at room temperature and 632.5 nm. Finally, we used the Kur...

An exhaustive study of the phase diagram of binary system Li 2 SO 4 -Na 2 SO 4 is presented. Phase diagram was determined using thermo-X-ray diffraction in powder samples and calorimetry ATD. A new phase with formula Li 2-x Na x SO 4 has been obtained, with 1 ≤ x ≤ 1.22. The crystal structure of β-LiNaSO 4 was determined from single-crystal X-ray diffraction. This study shows that the crystals usually become twinned when the growth is by solution; which explains the poor spontaneous polarization. The Raman dispersion of Li 2 SO 4 , Na 2 SO 4 and LiNaSO 4 compounds is explained from the structural data. The measurements have been made at different heating and cooling rate.

We used X-ray single-crystal diffraction (XRD) and high-resolution neutron powder diffraction (NPD) and performed second-harmonic generation (SHG) measurements to investigate the structural details and nonlinear optical (NLO) properties of Rb0.855Ti0.955Nb0.045OPO4 and RbTi0.927Nb0.056Er0.017OPO4. We studied in detail the distribution of Nb5+ and Er3+ doping cations among the different types of TiO6 octahedra in the structure. We found that Nb cations exclusively occupied Ti(1) sites, but we did not observe a preferential occupation of the octahedra by Er. Our results established that, in Rb0.855Ti0.955Nb0.045OPO4, the substitution of Ti4+ by Nb5+ centers was compensated by the creation of Rb+ vacancies. The SHG measurements in these crystals reveal that these crystals are excellent nonlinear optical materials and that the absorption of the generated green light by Er3+ in the RbTi0.927Nb0.056Er0.017OPO4 crystal is negligible.

The 1,4-benzodioxin-2-carboxylic esters or carboxamides react with nucleophilic amines to give access to 3-hydroxy-2,3-dihydro-1,4-benzodioxin-2-carboxamides and 3-aminomethyn-1,4-benzodioxin-2(3 H )-one precursors of potential therapeutical compounds. The basic environment (K 2 CO 3 or amine) facilitates the process.

The crystal structure of monoclinic KYb(WO4)2(KYbW) crystals has been refined (in space groupC2/c) at room temperature by using single-crystal X-ray diffraction data. KYbW undoped crystals were grown by the TSSG (top-seeded-solution growth) slow-cooling method. The crystals show {110}, {\bar{1}11}, {010} and {310} faces, which basically define their habit. The linear thermal expansion tensor has been determined and the principal axis with maximum thermal expansion (\alpha ^{\,\prime}_{33} = 16.68 × 10−6 K−1), {\bf X}^{\,\prime}_{3}, was located 12° from thecaxis. Its principal {\bf X}^{\,\prime}_{1}, {\bf X}^{\,\prime}_{2} and {\bf X}^{\,\prime}_{3} axes are [302], [010] and [106] directions, respectively, in the crystallographic system. The optical tensor has been studied at λ = 632.8 nm at room temperature; two principal axes,NgandNm, are located in theacplane, while the other,Np, is parallel to [010]. The principal axis with maximum refractive index (ng= 2.45),Ng, was located 19° from thecaxis.

The crystal structure of monoclinic KGd(WO4)2(KGW) has been refined at room temperature by using single-crystal X-ray diffraction data. The unit-cell parameters area= 10.652 (4),b= 10.374 (6),c= 7.582 (2) Å, β = 130.80 (2)°, withZ= 4, in space groupC2/c. The linear thermal expansion tensor has been determined and the principal axes are [302], [010] and [106]. The principal axis with maximum thermal expansion (\boldalpha'_{33} = 23.44 × 10−6 K−1), {\bf X}'_{3}, was located 12° from thecaxis. Undoped crystals of KGW and crystals that were partially doped by Pr, Nd, Ho, Er, Tm and Yb were grown by the top-seeding-solution growth slow-cooling method. The effect of doping on the KGW structure was observed in the cell parameters and in morphological changes. The changes in parameters follow the changes in lanthanide ionic radii. The doped crystals show {021} and {\bar{2}21} faces in addition to the {110}, {\bar{1}11}, {010}, {130} and {310} faces which basically follow the habit of the undoped KGW crystals. The development of the faces is related to the number of the most important periodic bond chains parallel to them.

The preparation and characterization of mixed crystals with formula Li(NH 4 ) 1-x K x SO 4 has been carried out. The characterization was by thermal analysis (DSC and ATD), X-ray diffraction on powder and single crystal samples at variable temperature and Raman spectroscopy at variable temperature. Two type of phases have been obtained: A solid solution with 0.94 < X < 1, with the same phases to those observed in the LiKSO 4 , but new phases, which are not shown by the LiKSO 4 , can be obtained according to the crystallization process. The second type of compounds have the formula Li(NH 4 ) 0.53 K 0.47 SO 4 , with an hexagonal structure (a 3 a LiKSO4 ). This compound have a phase transition at 463K.

In the present work, potassium titanyl phosphate single crystals doped with different levels of Ge4+, Zr4+, and Ce4+ were successfully grown by flux using the top-seeded solution growth (TSSG) method. Their saturation temperatures and crystal habits were compared with those of the undoped single crystals and some differences were observed. In addition, the distribution coefficients of the different dopants were also determined and found to be in correlation with the ionic radii of the M4+ ions. Zr4+ doping gives the most suitable distribution coefficient, does not introduce problematic absorption bands in the visible region, and significantly reduces the ionic conductivity in the c direction.

Pd(II) and Pt(II) complexes of formulae [MLCl2], where L = mepirizole, were synthesized and characterized. Two complexes were obtained and studied by different techniques: IR, 1H and 13C NMR and XPS spectroscopies and mass spectrometry (electrospray). The crystal structure of the complex cis-dichloro-4-methoxy-2-(5-methoxy-3-methyl- pyrazol-1-yl)-6-methyl-pyrimidinepalladium(II), [Pd(mep)Cl2], was studied by crystal X-ray diffraction. It consists of discrete molecules with planar geometry. Pd(II) ions are four-coordinated by two mepirizole nitrogen atoms (N1 from the pyrazole ring and N4 from the pyrimidine ring) and two chlorine atoms. The geometry of the PdN2Cl2 chromophore is a distortion of the square-planar coordination. Data from powder pattern X-ray diffraction of cis-dichloro-4-methoxy-2-(5-methoxy-3-methyl-pyrazol-1-yl)-6-methyl- pyrimidineplatinum(II), [Pt(mep)Cl2], demonstrated that the two complexes are isostructural. The cytotoxic activity of both Pd and Pt complexes was checked for six different tumor cell lines and was lower than that of cisplatin. The Pt bound to DNA was also checked and only a low percentage is able to cross the cell membrane.

KGd(WO4)2 single crystals doped with Er3+ have been grown by the flux top-seeded-solution growth method. The crystallographic structure of the lattice has been refined, being the lattice constants a=10.652(4), b=10.374(6), c=7.582(2) Å, β=130.80(2)°. The refractive index dispersion of the host has been measured in the 350–1500 nm range. The optical absorption and photoluminescence properties of Er3+ have been characterised in the 5–300 K temperature range. At 5 K, the absorption and emission bands show the (2J+1)/2 multiplet splittings expected for the C2 symmetry site of Er in the Gd site. The energy positions and halfwidths of the 72 sublevels observed have been tabulated as well as the cross sections of the different multiplets. Six emission band sets have been observed under excitation of the 4F7/2 multiplet. The Judd–Ofelt (JO) parameters of Er3+ in KGW have been calculated: Ω2=8.90×10-20 cm2, Ω4=0.96×10-20 cm2, Ω6=0.82×10-20 cm2. Lifetimes of the 4S3/2, 4F9/2, and 4I11/2 multiplets have been measured in the 5–300 K range of temperature and compared with those calculated from the JO theory. A reduction of the 4S3/2 and 4I11/2 measured lifetimes with increasing erbium concentration has been observed, moreover the presence of multiphonon non-radiative processes is inferred from the temperature dependence of the lifetimes., This work has been supported by CICyT under project number TIC96-1039.

Eleven alkaloids have been isolated from whole plants of Narcissus bujei (Amaryllidaceae). The alkaloids 11-Oacetylhaemanthamine and bujeine are reported for the first time. The structure and stereochemistry of these new alkaloids have been determined by physical and spectroscopic methods. The X-ray diAraction analysis of O-methyllycorenine hydrochloride has been performed. # 1998 Elsevier Science Ltd. All rights reserved.

Two Pd(II) complexes and two Pt(II) complexes of formula [PdLCl2], [PdL2](ClO4)2, [PtLCl2] and [Pt2L2Cl2]Cl2, respectively, where L=ethylthioethylamine, were synthesized and characterized by the usual spectroscopic techniques. Crystal structures of the palladium complexes were determined by X-ray diffraction. The ligand binds to the metal ion in bidentate fashion through the sulfur and nitrogen atoms, in both cases. The reactivity of the complexes with calf thymus and pBR322 plasmid DNA was studied by CD and electrophoretic mobility respectively. No changes affecting the secondary or tertiary DNA structure were observed.

Thermal analysis, powder diffraction, and Raman scattering as a function of the temperature were carried out on ${\mathrm{K}}_{2}{\mathrm{BeF}}_{4}.$ Moreover, the crystal structure was determined at 293 K from powder diffraction. The compound shows a transition from ${\mathrm{Pna}2}_{1}$ to $\mathrm{Pnam}$ space group at 921 K with a transition enthalpy of 5 kJ/mol. The transition is assumed to be first order because the compound shows metastability. Structurally and spectroscopically the transition is similar to those observed in ${(\mathrm{N}\mathrm{H}}_{4}{)}_{2}{\mathrm{SO}}_{4},$ which suggests that the low-temperature phase is ferroelectric. In order to confirm it, the spontaneous polarization has been computed using an ionic model.

The crystal structures of methyl and ethyl N-(2,3-dimethoxybenzyl)-N-(p-toluenesulfonyl)-2-phenyl-glycinates 4a and 4b respectively, have been determined by X-ray diffraction analysis. The presence of different alkyl ester groups in both molecules does not affect the geometry retaining a synclinal conformation for the N atom and the O atom of the C=O group [N-C17-C18-O5 38.1(5)° for 4a and 33.3(4)° for 4b].

Pd(ll) and Pt(ll) complexes of three series of Schiff thiobases derived from 2- carbonylpyridine have been synthesized and characterized. The crystal structure of the Pt(ll) derivative of methyl-3-(2-pyridylmethylene)hydrazinecarbodithioate (HFp) was resolved. The ligand coordinates the platinum ion in tridentate fashion by heterocycle and imine nitrogen and thiocarbonyl sulfur. The fourth ligand is a chloride ion. The structure of the complexes is suitable for the formation of monofunctional adducts with DNA. Studies on the interaction of the complexes with Calf thymus DNA by CD reveal modifications in the B form of lineal DNA. Interaction with plasmid DNA was also confirmed in the images obtained by atomic force microscopy.

The effect of five derivatives of PtII, cis dichloro-(1,2-dimethyl-3-aminopyrrolidine)platinum(II), cis dichloro-(1-methyl, 2-ethyl-3-aminopyrrolidine)platinum(II), cis dichloro-(1-ethyl, 2-methyl-3-aminopyrrolidine)platinum(II), cis dichloro-(1,2-diethyl-3-aminopyrrolidine)platinum(II), and cis dichloro-(1-propyl, 2 methyl-3 aminopyrrolidine)platinum(II) on platination of DNA was studied by CD and melting temperature determination. Reactions with the nucleotides d(ApG) and d(ApA) were also followed by 1H NMR and CD, indicating binding via N(7) and formation mainly of bifunctional, in the case of d(ApG), or monofunctional adducts, in the case of d(ApA). The crystal structure of cis dichloro-(1 ethyl, 2 methyl-3 aminopyrrolidine)platinum(II) shows the analogues cisplatin structure of these active antitumour complexes. This compound is racemic.

The crystal structures of potassium strontium tetraborate decahydrate, K2Sr[H4B4O9]2.10H2O, and ammonium calcium tetraborate octahydrate, (NH4)2Ca[H4B4O9]2.8H2O, have been determined. The two structures have similar cell parameters but different space groups. The first compound is homeotypic and the second is isotypic with potassium calcium tetraborate octahydrate and rubidium strontium tetraborate octahydrate. The structures contain alternate layers of tetraborate ions and two of the water molecules, along with the cations and the remaining water molecules. The cation size and the hydrolysis constant of each cation define the space group and the number of water molecules of hydration.

The crystal structure determination of Rochelle salt [KNa(C4H4O6)·4 H2O] at 213, 274, and 323 K has been carried out. Crystals at 213 K are orthorhombic,P21212, witha=11.880(3),b=14.298(3),c=6.216(2)A,Z=4,R(F)=0.040. At 274 K crystals are monoclinic,P21, witha=11.869(3),b=14.316(8),c=6.223(3)A,α=89.26(4)°,Z=4,R(F)=0.072. At 323 K they are orthorhombic,P21212, witha=11.924(3),b=14.298(3),c=6.230(2)A.Z=4,R(F)=0.073. Two kinds of polarized chain in the ferroelectric phase (274 K) are observed, one similar to those found at the high-temperature paraelectric phase (323 K) and the other similar to those found at the low-temperature paraelectric phase (213 K). The paraelectric crystal structures do not show disorder or anisotropic thermal parameters which justify the hypothesis that the paraelectric–ferroelectric transition was of the order–disorder type. A study of powder diffraction, the momentum of inertia of tartrate ions, and the librational and translation tensor confirms that the transition is second order, and the independence of the two kinds of chains. A structural and thermodynamic model is proposed from these results. The ferroelectric phase is an “ordered” solid solution of two kinds of chains, which is explained from a regular model, according to which the ΔHbetween the two paraelectric phases is 485 cm−1andwfor the solid solution is 152 cm−1.

The synthetic routes of 6,7-dihydrobenzo[4,5]cyclohept[1,2-b]indol-12(5H)-one 5 from either 1-methyl or 1-sulfonylindole-2-carboxaldehyde 1 or ethyl 1,2-dimethylindole-3-carboxylate 6 are reported. The structure of the ketone 5a was confirmed by X-ray crystallography. Several indole derivatives have been prepared with potential antitumor activity.

The preparation of stable Lewis base adducts of CuL (H2L=Schiff base derived from the condensation of o-hydroxypropiophenone (OHP) and salicylhydrazide (SHZ)) is described. The N-donors bipy and bipyam ligands (bipy=2,2′-bipyridyl; bipyam=2,2′-bipyridylamine) give the complexes [Cu(OHP-SHZ)(bipy)] (I) and [Cu(OHP-SHZ)(bipyam)]H2O (II) which have been characterized by physical and spectroscopic techniques. Crystals of I are orthorhombic, space group Pcab, with a=10.221(3), b=12.643(3), c=35.448(3) A, V=4581(2) A3 and Z=8. The structure of complex I is shown to comprise discrete monomeric [Cu(OHP-SHZ)(bipy)] molecules in which the Cu(II) atom environment exhibits a highly distorted five-coordinated geometry. Crystals of II are monoclinic, space group C2/c, with a=24.804(3), b=13.231(3), c=14.739(3) A, β=99.57(2)°, V=4770(2) A3 and Z=8. The structure of this complex consists of discrete entities associated into H-bonded binuclear units via the lattice water molecules. The coordination sphere around the copper center is nearly square pyramidal. The transition from a six-membered chelated ring to a five-membered one results in a less distorted coordination polyhedron around the Cu(II) ion. In both complexes the OHP-SHZ ligand occupies three of the coordination sites through the same (ONO) donor atoms while the remaining positions are occupied by the pyridine N atoms. EPR spectra provide evidence of the existence of very weak magnetic exchange coupling in the complex [Cu(OHP-SHZ)(bipyam)]H2O (II). Thermogravimetric and differential scanning calorimetric studies of complex I show that this complex loses the bipy molecule through an endothermic process with ΔH=81.75 kJ mol−1. The best kinetic parameter values corresponding to the process involving the loss of the bipy molecule were found on the basis of the agreement between non-isothermal and isothermal methods and are given by the Abou-Shaaban–Simonelli equation in isothermal conditions. The better representation of the reaction mechanism is the phase-boundary, spherical symmetry reaction.

The X-ray crystal structure of 4-phenyl-5-(2,3,4-trimethoxyphenyl)-isoxazole, C 18 H 17 NO 4 , (I) has been determined, revealing an interesting lack of coplanarity for the aromatic rings system. This preferred conformation implies reduction of the conjugation degree, as shown by the C(2)-C(10) and C(3)-C(4) bond-length values. The arrangement of the three methoxy substituents is also examined.

KTP single crystal have successfully been grown from neodymium modified tungstate fluxes, using the TSSG/slow cooling technique. EPMA and ICP analyses reveal the presence of both, neodymium and tungsten, elements in the KTP crystalline matrix. Crystallographic structure refinement made by X-ray diffraction shows that the tungsten impurities are located at the two titanium sites of the KTP structure. Optical transmission spectra are also characterized and discussed.

New cationic, [(Fp)Ph2PC⋮CPPh2(Fp)]2+ (1) and [(Fp)Ph2PC⋮CPPh2]+(2), and anionic, [Fe3(CO)9(μ3-CCH3)(Ph2PC⋮CPPh2)]- (3) and [{Fe3(CO)9(μ3-CCH3)}2(Ph2PC⋮CPPh2)]2- (4), P-coordinate complexes with bis(diphenylphosphino)acetylene have been prepared. The zwitterionic P-coordinated iron complex [{Fe3(CO)9(μ3-CCH3)}Ph2PC⋮CPPh2(Fp)] (5) has been synthesized in two different ways and characterized by X-ray crystallography.

A study on the mixed crystals of formula (NH4)2(SO4)X(BeF4)1-x has been carried out, using thermal analyses, X-ray diffraction on powder and single-crystal samples at different temperatures. It is shown that these mixed crystals are isomorphs, showing for × 0.5 the behavior is more similar to (NH4)2SO4, which is explained by the shortest ammoniumion hydrogen bond lengths for the majority component. The presence of second ion produces a delay in the transition temperature. And it has been studied the inhomogenity of mixed crystal, which difficults obtain the compound discontinuity of two behaviors.

The development of processes for C C bond formation is at the heart of chemistry. Indeed, the development of the catalytic version of such reactions is highly valuable and beneficial. Theoretical analyses have critically contributed to the improvement and the understanding of their reaction mechanisms. Two of the most important catalytic processes developed for generating single and double C–C bonds are described from a molecular perspective: cross-coupling and metathesis reactions. Although these reactions were discovered at the end of the twentieth century, it has been during the twenty-first century that the major contributions to the comprehension of their reaction mechanisms have been achieved. Here, we review the most important computational contributions on these two reactions.

The crystal structures of 3,4-bis(tert-butoxy)-2,4-cydopentadien-1-one, C 13 H 20 O 3 , and fac-[η 5 -3,4-bis(tert-butoxy)-2,4-cyclopentadien-1-one]tricarbonyl iron(0), [Fe(C 13 H 20 O 3 )(CO) 3 ], have been determined. The organic compound is planar with the positions of the double bonds well defined. The inclusion of an Fe(CO) 3 moiety induces a loss of planarity, producing an envelope form and delocalization of the double bonds.

Dichromates of 2,4′-bipyridine (two forms), [(H2-2,4′-bipy)(Cr2O7)] (1) and [(H-2,4′-bipy)2(Cr2O7)] (2), 2,2′-dipyridylamine, [(H-dpam)2(Cr2O7)] (3), and 4,4′-bipyridine (two forms), [(H2-4,4′-bipy)(Cr2O7)] (4) and [(H-4,4′-bipy)2(H2-4,4′-bipy)(Cr2O7)2] (5), were prepared by reaction of chromium(VI) oxide with the free organic bases in the appropriate stoichiometric ratio in water at 25°C. The structures of compounds 2, 3 and 4 were determined by X-ray crystallography and revealed the existence of discrete dichromate anions formed by two tetrahedral CrO4 groups joined through shared O atoms, and the respective protonated organic bases hydrogen bonded to respective dinegative anions. A short CH…O interaction [2.996(4) A] between the organic cation and the dichromate anion was observed in compound 4. All organic dichromates were also characterized by IR, UV-vis 1H NMR measurements. For compounds 2, 3 and 4, a comparison was made and the crystallographic data of a series of mono- and polychromates and showed a correlation of the terminal and bridging CrO atomic distances with an increasing degree of polymerization. A graph theory cluster expansion was employed for these correlation studies.

The coordinatively unsaturated 16-electron complexes Ru(HCCHR)Cl(CO)(PPh3)2 (RtBu and Ph) react with the sodium salts of functionalized carboxylates NaO2CR′ (R′MeCHCHCHCH, CH2CHCH2, PhCC and MeCC) to give saturated complexes of formulae Ru(HCCHR)(O2CR′)(CO)(PPh3)2, where the carboxylate group acts as an η2-coordinated ligand. The structure of the complex Ru(HCCHPh)(O2CCHCHCHCHCH3)(CO)(PPh3)2 has been determined by X-ray diffraction. Crystals are monoclinic, space group P21/n with dimensions of the unit cell of a = 12.191(3), b = 18.596(4), c = 20.001(4) A , β = 107.23(3)° and Dx = 1.331 g cm−3 for Z = 4. All the complexes have been identified by IR, 1H NMR and 31P NMR spectroscopies, and from their C and H elemental analyses.

The application of the cyclopalladated compound [Pd(2-{Z-( R )-CHMeN=CH-2′,6′-Cl 2 C 6 H 3 }C 6 H 4 )Cl] 2 for the enantiomeric excess determination of functionalized phosphines is presented. The X-ray structure determination of diastereomeric complex [Pd(2-{Z-( R )-CHMeN=CH-2′,6′-Cl 2 C 6 H 3 }C 6 H 4 )Cl{( R , R )-PPh 2 (2-OHC 6 H 1 0 )}] is also reported.

The crystal structure of the title compound, C 24 H 27 NO 5 S, was determined. The sum of the bond angles around the N atom is 356.6°, showing sp 2 character. The torsion angle N-C(10)-C(17)-O(3) [−179.0 (2)°] characterizes the antiperiplanar conformation for the N and O atoms. The crystal structure is stabilized by hydrogen bonds [C(9)-H(9)...O(4) and C(20)-H(20)...O(1)] and van der Waals forces

The structures of benzyl 2-[N-benzyl-N-(p-toluenesulfonyl)amino]-2-phenylacetate, C 29 H 27 NO 4 S, (I), and 2-[N-benzyl-N-(p-toluenesulfonyl)amino]-2-phenylacetic acid, C 22 H 21 NO 4 S, (II), have been determined. The geometries of both compounds are similar. The N atoms and the carboxylic C atoms are sp 2 hybridized. The N-C(8)-C(9)-O(3) torsion angle in compound (I) [-18.4 (5) o ] and the N-C(8)-C(15)-O(4) torsion angle in compound (II) [9.6 (4) o ] characterize a synperiplanar conformation for the N atom and the O atom of the C=O group in both compounds studied

5,7-Trifluoromethyl-6-fluoro-2,3-dihydro-1 H -1,4-diazepine has been prepared by the reaction of perfluoropent-2-ene (or 2-amino-4-iminoperfluoropent-2-ene) with ethylenediamine. Both perfluoropent-2-ene and 2-amino-4-iminoperfluoropent-2-ene were found to react with diethylenetriamine to form 1,9-trifluoromethyl-3,4,6,7-tetrahydro-2 H -pyrazino[1,2 a ]pyrazine (established by X-ray study). Some salts and the complex with BF 3 of this bicyclic compound are described.

The reaction of 2-chloro-3,5-dinitropyridine with two equivalents of KN3 in the presence of ROH results in stable Meisenheimer-type σ-adducts of 4,6-dinitrotetra-zolo[1,5-a]pyridine with RO− anions (R = H, Alk, Ph). The mechanism of σ-complex formation was suggested. The structure of the σ-adduct with R = Me was established by IR and NMR spectroscopy and by X-ray diffraction analysis.

The transamination of 2-amino-4-imino-2-perfluoropentene with ethylenediamine gives the corresponding 6-fluoro-5,7-bis(trifluoromethyl)-2,3-dihydro-1H-1,4-diazepine. The transamination of 2-amino-4-imino-2-perfluoropentene by diethylenetriamine is accompanied by intramolecular nucleophilic substitution of the α-fluorine atom to form 1,9-bis(trifluoromethyl)-3,4,6,7-tetrahydro-2H-pyrazino[1,2-a]pyrazine whose structure was established by an X-ray structural investigation. Several salts of this bicyclic compound and its complex with BF3 have been described.

The crystal structures of tetrasodium (1,2-ethanediyldinitrilo)tetraacetate pentahydrate and disodium dihydrogen (1,2-ethanediyldinitrilo)tetraacetate dihydrate have been determined. Na ions prefer to act as bridges between different edta ligands and only in the tetrasodium salt is the edta ligand hexadentate to one Na ion. Na ions display seven-coordination, when coordinated to one edta ligand (distorted pentagonal bipyramid), and six-coordination, when linked to several edta ligands (from distorted octahedral to trapezoidal bipyramidal geometry). An Na ion in the tetrasodium salt shows five-coordination, because the sixth site is blocked by the edta ligand

(NH4)2BeF4in its normal phase presents an incommensurate phase between -90 and -96°C and becomes ferroelectric at temperatures below -96°C. The Tl2BeF4has been synthesized and its crystal structure has been resolved. The existence of solid solutions of general formula (NH4)2-xTlxBeF4(2>x>0) is confirmed. From the study of these solid solutions by X-ray diffraction we can say that, the substitution of ammonium by thallium precludes the paraelectric-ferroelectric phase transition of (NH4)2BeF4. The displacement of the NH4 groups is hindered by thallium which disrupts the lattice periodicity. On the other hand the same thallium does not seem to have such an important influence on the twist of BeF4groups. The presence of thallium in (NH4)2BeF4precludes the phase transition, which indicates that the NH4+ ions play a most important role in triggering the phase transition.

The interaction of methazolamide (Hmacm) with Ni(II) ion and ammonia molecules gives rise to the complex of formula [Ni(macm)2(NH3)4]. The complex crystallizes in the monoclinic P21/n space group with a = 14.255(4), b = 7.126(2), c = 12.444(3) A, β = 113.12(3)° and Z = 2. The structure was refined to R = 0.065 (Rw = 0.065). The complex consists of monomeric units which interact through hydrogen bonds and van der Waals contacts. The Ni(II) ion is coordinated with the deprotonated sulfonamido nitrogen of the macm− ligand in axial sites and the ammonia molecules in equatorial positions. IR, electronic spectra and 1H NMR results are also reported.