Concepción Foces-Foces

Indenyl complexes of ruthenium(II). Crystal structure of [Ru(CO)(PPh3)2(η5-C9H7)]ClO4·12CH2Cl2

Abstract The compound [RuCl(PPh3)2(η5-C9H7)] (I) has been made in high yield by reaction of [RuCl2(PPh3)3] with indene and potassium hydroxide in ethanol and its reactions have been examined. Complex I reacts with appropriate nucleophiles to give the complexes [RuX(PPh3)2(η5-C9H7)] (X = H, CH3, I, SnCl3, C2Ph) and [RuCl(dppe)(η5-C9H7)]. Heating of complex I with methanol in a sealed tube leads to the elimination of the indenyl group and decarbonylation of methanol. Cationic complexes of formulae [RuL(PPh3)2(η5-C9H7)]ClO4 (L = CH3CN, 2-ClC6H4CN, CH2CHCN, 1,2-(CN)2C6H4, C2H4(CN)2, N2H4, CNBut, CO, CCHPh, and C2H4) and [Ru(L-L)PPh3(η5-C9H7)]ClO4 (L-L = 2,5-norbornadiene (nbd), tetrafluorobenzobarrelene (tfb), ethylenediamine (en), propylenediamine (pn), biimidazole (Hbim), 2,2′-bipyridine (bipy) and 1,10-phenanthroline (phen)) are obtained by treatment of complex I with the appropriate ligand and sodium perchlorate in methanol. Reaction of the vinylideneruthenium complex [Ru(η1-CCHPh) (PPh3)2(η5-C9H7)]ClO4 with oxygen gives [Ru(CO)(PPh3)2(η5-C9H7)]ClO4. The structure of [Ru(CO)(PPh3)2(η5-C9H7)]ClO4· 1 2 CH2Cl2 has been determined by X-ray diffraction. The space group is P 1 with lattice constants a 18.5513(14), b 12.9165(5), and c 9.6898(5) A, and α 80.942(5), β 104.998(7) and γ 111.130(4)°. Final R and Rw factors are 0.039 and 0.043, respectively, for the 6836 observed data (3σ(I) criterion). The metal is bonded to an indenyl group through the five-membered ring, and hexacoordination of the ruthenium atom is completed by two triphenylphosphine ligands and a carbonyl group.

The geometry of pyrazole: A test for ab initio calculations

Ab initio calculations on the structure of pyrazole have been carried out at different levels of accuracy. At the Hartree‐Fock (HF) level, the performance of several basis sets, namely 3‐21G, 6‐31G, 6‐31G**, and 6–311G** was investigated. The influence of electron correlation effects also was studied by carrying out geometry optimizations at the MP2, MP4, and QCISD levels. The performance of a density functional method also was evaluated. We have also investigated the possible influence of the frozen core approximation on the final optimized geometry. Three different statistical analyses were considered in determining which geometry is closest to the experimental microwave geometry—namely Paul Curtins diagrams, cluster analysis, and multidimensional scaling. From these analyses, we conclude that there is no asymptotic approach to the experimental geometry by increasing the quality of the theoretical model, although, as expected, the more reliable structures are those obtained at the MP2, MP4, and QCISD levels, as well as those obtained by the B3LYP density functional method. We have also found that the values of the rotational constants are a tight criterion to define the quality of a molecular geometry.

Basicity of N-H- and N-Methyl-1,2,3-triazoles in the Gas Phase, in Solution, and in the Solid State − An Experimental and Theoretical Study

The gas-phase and aqueous basicities of six 1,2,3-triazoles have been determined, the former by FT-ICR and the latter by spectrophotometry and 1H NMR. The gas-phase experiments agree very well with the Gibbs free energies calculated at the B3LYP/6-31G* level. In contrast, only semiquantitative ascertainments are possible when basicities in the gas phase and in solution are compared. It is possible, with the aid of calculations, to obtain a complete picture of the complex equilibria involved in C-substituted N-H-1,2,3-triazoles. The crystal structures of 4(5)-phenyl-1,2,3-triazole (4) and 4(5)-nitro-1,2,3-triazole (15) have been determined. In the gas phase, 2H tautomers b always predominate, while in aqueous solution, both 1H and 2H tautomers − a and b − are present. Finally, in the solid state, 1 exists as a 1:1 mixture of 1a and 1b, while 4 is in the 4b tautomeric form and 15 is a 1H tautomer 15a. These conclusions − a in the gas phase, a + b in solution, and equal probabilities of finding either a or b in the crystal − are probably general for all 1,2,3-triazoles.

Structural Determinants of Tissue Tropism and In Vivo Pathogenicity for the Parvovirus Minute Virus of Mice

ABSTRACT Two strains of the parvovirus minute virus of mice (MVM), the immunosuppressive (MVMi) and the prototype (MVMp) strains, display disparate in vitro tropism and in vivo pathogenicity. We report the crystal structures of MVMp virus-like particles (MVMpb) and native wild-type (wt) empty capsids (MVMpe), determined and refined to 3.25 and 3.75 Å resolution, respectively, and their comparison to the structure of MVMi, also refined to 3.5 Å resolution in this study. A comparison of the MVMpb and MVMpe capsids showed their structures to be the same, providing structural verification that some heterologously expressed parvovirus capsids are indistinguishable from wt capsids produced in host cells. The structures of MVMi and MVMp capsids were almost identical, but local surface conformational differences clustered from symmetry-related capsid proteins at three specific domains: (i) the icosahedral fivefold axis, (ii) the “shoulder” of the protrusion at the icosahedral threefold axis, and (iii) the area surrounding the depression at the icosahedral twofold axis. The latter two domains contain important determinants of MVM in vitro tropism (residues 317 and 321) and forward mutation residues (residues 399, 460, 553, and 558) conferring fibrotropism on MVMi. Furthermore, these structural differences between the MVM strains colocalize with tropism and pathogenicity determinants mapped for other autonomous parvovirus capsids, highlighting the importance of common parvovirus capsid regions in the control of virus-host interactions.

Dihydrogen bonds (A–H⋯H–B)

Theoretical calculations up to MP2/6–31G** with BSSE correction are carried out on a series of A–H⋯H–B dihydrogen bonds (A = B, Li, Be; B = N, C).

SYNTHESIS AND MOLECULAR STRUCTURE OF 3-(2-BENZYLOXY-6-HYDROXYPHENYL)-5-STYRYLPYRAZOLES. REACTION OF 2-STYRYLCHROMONES AND HYDRAZINE HYDRATE

Abstract 3-(2-Benzyloxy-6-hydroxyphenyl)-5-styrylpyrazoles 7a-e were prepared from the reaction of 2-styrylchromones and hydrazine hydrate. 3-(2-Benzyloxy-6-hydroxyphenyl)-5-(2-phenylethyl)-pyrazoles 8a,d,e and 3-(2-benzyloxy-β,6-dihydroxystyryl)-5-aryl-2-pyrazolines 9a-e were also obtained as by-products. The crystal and molecular structure of two 3-(2-benzyloxy-6-hydroxyphenyl)-5-styrylpyrazoles 7a,b have been determined by X-Ray analysis. Although the substitution of an hydrogen by a methyl group on the double bond of the styryl moiety seems to be a minor perturbation, it produces drastic changes in the crystal packing where only one conformer is present. The OH group is involved as donor of an intramolecular hydrogen bond and the NH group is responsible for the formation of chains via intermolecular hydrogen bonds.

Tris(pyrazol-1-yl)methane-rhodium(I) and -iridium(I) complexes; cyrstal structure of [Rh(COD)(tpzm)][RhCl2(COD)]·3CHCl3

Abstract Fourteen new rhodium and iridium complexes of the tris(pyrazol-1-yl)methane (tpzm) ligand have been prepared. They are of the three types [MCl(diolefin)(tpzm)], [M(diolefin)(tpzm)]Clo 4 , and [M(diolefin)(tpzm)] [MCl 2 (diolefin)], where M is Rh I of Ir I and (diolefin) is a cyclic diolefin (1,5-cyclooctadiene, bicyclo-2,2,1-heptadiene, 5,6,7,8-tetrafluoro-1,4-dihydro-1,4-ethenoaphtalene, or 1,3-dimethyl-5,6,7-,8-tetrafluoro-1,4-dihydro-1,4-ethenonapthalene, or 1,3-dimethyl-5,6,7,8-tetrafluoro-1,4-dihydro-1,4-[9-methyletheno]-napthalene). Addition of [IrCl(COD)] 2 to [RhCl(COD)(tpzm)] gives the complex [Ir(COD)(tpzm)] [RhCl 2 (COD)] owing to the greater tendency of iridium to form five-coordinated species. The crystal structure of [Rh(COD)(tpzm)] [RhCl 2 (COD)] has been determined by X-ray diffraction. The space group is P 1 with a 12.4256(21), b 15.4113(25), c 12.0152(16) A, α 101.48(1), β 105.03(1) and λ 67.21(1)°. The complex exhibits an ionic dinuclear structure and crystallizes with six CHCl 3 molecules per unit cell. In the anion, the Rh(2) atom is in a square-planar arrangement and in the cation the coordination around Rh(1) is that of a distorted trigonal bipyramid. A careful 13 C and 1 H NMR spectra study has been carried out, with particular emphasis on the assignment of the pyrazole signals. The shifts induced by complexation (larger in the 1 H NMR spectra for iridium than for rhodium), the dynamics aspects, and the COD signals are discussed.

Glycosyl Inositol Derivatives Related to Inositolphosphoglycan Mediators: Synthesis, Structure, and Biological Activity

17 paginas, 12 figuras, 4 esquemas, 7 tablas.-- Supporting information for this article is available on the WWW under http://www.wiley-vch.de/home/chemistry/ or from the author.

The influence of the substituent at the nitrogen atom on the molecular structure of pyrazoles: a crystallographic statistical survey versus ab initio calculations

Abstract A survey of the crystal structures of pyrazoles reported in the Cambridge Structural Database has been analyzed using the diagrams of Dieterich. (D.A. Dieterich, I.C. Paul and D.Y. Curtin, J. Am. Chem. Soc., 96 (1974) 6372). Structures have been classified according to the substituent at position 1 of the pyrazole ring. A total of 209 data were analyzed. For eight representative N -substituents (H, CH 3 , CHO, NH 2 , NO 2 , PH 2 , BH 2 and BH − 3 ) ab initio calculations at the 6-31G** level have been carried out. The average geometries for these groups of pyrazoles and those calculated theoretically are generally in good agreement considering the assumed simplifications (not taking into account the effect of the C-substituents, reduction of the N-substituent to its simpler expression). The effect of substituents on nitrogen parallels that on carbon in benzene rings with the exception of the amino group.

Unexpected Staudinger reaction of α-azidoacetonitriles α-phenyl substituted with triphenylphosphine. Preparation, X-ray crystal and molecular structures of a phosphazine, an aminophosphonium carbanion salt and a phosphazide, with (Z)-configuration

Abstract Staudinger reaction of α-azidophenylacetonitrile with triphenylphosphine in 1:2 molar ratio provides the triphenylphosphazine 4 derived from α-diazophenylacetonitrile, whereas in 2:1 molar ratio the final product is found to be the aminotriphenylphosphonium salt of phenylmalononitrile 6 . However, the Staudinger reaction of α-azidodiphenylacetonitrile with triphenylphosphine affords the corresponding (Z)-phosphazide 17 . The crystal and molecular structures of compounds 4,6 , and 17 have been determined by X-ray analysis. Compound 17 is the first isolated phosphazide which presents the (Z)-configuration with respect to the central N-N bond of the PN 3 C moiety (P-N-N-N=0.0(3)°).