Two coordination compounds of SnCl2 with 4-methylpyridine N-oxide

In the solid-state structures of catena-poly[[dichloridotin(II)]-μ2-(4-methylpyridine N-oxide)-κ2 O:O], [SnCl2(C6H7NO)] n , 1, and dichloridobis(4-methylpyridine N-oxide-κO)tin(II), [SnCl2(C6H7NO)2], 2, the bivalent tin atoms reveal a seesaw coordination with both chlorine atoms in equatorial and the Lewis base molecules in axial positions. While the Sn—Cl distances are almost identical, the Sn—O distances vary significantly as a result of the different bonding modes (μ2 for 1, μ1 for 2) of the 4-methylpyridin-N-oxide molecules, giving rise to a one-dimensional coordination polymer for the 1:1 adduct, 1, and a molecular structure for the 1:2 adduct, 2. The different coordination modes also influence the bonding parameters within the almost planar ligand molecules, mostly expressed in N—O-bond lengthening and endocyclic bond-angle widening at the nitrogen atoms. Additional supramolecular features are found in the crystal structure of 2 as two adjacent molecules form dimers via additional, weak O...Sn interactions.

3,5-Dibromobenzonitrile

Molecules of the title compound (I), C7H3Br2N, lie on a crystallographic mirror plane that bisects the benzene ring and the cyano group. In the crystal, no C[triple-bond]N...Br or Br...Br short contacts are observed. Head-to-tail C(7) chains form based on weak hydrogen bonding between the the para H atom and the cyano N atom. Although molecules of (I) pack differently than 3,5-difluorobenzonitrile, both compounds have similarly distorted benzene rings. For (I), the endocyclic bond angles are 121.16 (16)° and 117.78 (16)° about the ipso and para C atoms, respectively.

5-cis-Bromo-2,2,6,6-tetramethyltetrahydropyran-3-carboxylic acid

Enantiomers of the title compound, C10H17BrO3, form hydrogen-bonded centrosymmetric dimers, where the carboxy H atom serves as donor and the C=O group of a neighbouring molecule acts as acceptor. The proximity of two axial methyl substituents causes distortions of the tetrahydropyran chair conformation, which are evident from the magnitude of the endocyclic bond angle at the O atom and the values of the endocyclic torsion angles.

cis-5-Bromo-2,2,6-trimethyl-trans-6-phenyltetrahydropyran-3-carboxylic acid

Centrosymmetric hydrogen-bonding between carboxy substituents links enantiomers of the title compound, C15H19BrO3, into dimers. Close contacts that originate from axially arranged methyl substituents in positions 2 and 6 induce distortions, which are evident from a widening of the endocyclic bond angle at the ring O atom [122.6 (6)°] and a flattening of the tetrahydropyran chair.

Comparative analysis of the trypanocidal activity and chemical properties of E-lychnophoric acid and its derivatives using theoretical calculations

E-Lychnophoric acid 1, its derivative ester 2 and alcohol 3 killed 100% of trypomastigote blood forms of Trypanosoma cruzi at the concentrations of 13.86, 5.68, and 6.48 µg/mL, respectively. Conformational distribution calculations (AM1) of 1, 2 and 3 gave minimum energies for the conformers a, b, c, and d, which differ from each other only in the cyclononene ring geometry. Calculations (DFT/BLYP/6-31G*) of geometry optimization and chemical properties were performed for conformers of 1, 2, and 3. The theoretical results were numerically compared to the trypanocidal activity. Calculated values of atomic charge, orbital population, and vibrational frequencies showed that the C-4-C-5 pi-endocyclic bond does not affect the trypanocidal activity of the studied compounds. Nevertheless, the structure of the group at C-4 strongly influences the activity. However, the theoretical results indicated that the intra-ring (C-1 and C-9) and pi-exocycle (C-8 and C-14) carbons of caryophyllene-type structures promote the trypanocidal activity of these compounds.

Crystal chemistry of tetraradial species. Part 7. Lithium tetrakis(1-imidazolyl)-borate solvate, Liiv[Liiv(H2O)(MeOH)]-[B(C3H3N2)4]2•MeOH, a 3-dimensional polymer; with observations on the geometry of imidazole rings

The title compound is a 3-dimensional polymer with a completely ordered triclinic structure [Formula: see text] a = 12.380(2) Å, b = 14.434(2) Å, c = 9.683(3) Å, α = 90.36(2)°, β = 105.44(2)°, γ = 90.75(2)°, Z = 2). Every B atom is tetrahedrally coordinated by N(1) atoms of the imidazole rings, every Li(1) atom is tetrahedrally coordinated by N(3) atoms, and every Li(2) atom is coordinated by two N(3) and two oxygen atoms, one from the H2O molecule and one from a MeOH molecule. The imidazole rings connected by the B—N(1) and Li—N(3) bonds thus generate a 3-dimensional covalent polymeric network. The MeOH molecules of coordination are hydrogen-bonded to unengaged N(3) atoms, thereby supplementing the covalent bonding system. The H2O molecules are hydrogen-bonded to the MeOH molecules of solvation to form centrosymmetric [Ow … OMeOH]2 rings, which in turn are connected to the covalent network by OMeOH—H … N(3) bonds to the remaining unengaged N(3) atoms. Every atom in the structure except the H(C) hydrogens is thus involved in the 3-dimensional bond system. The excellent consistency of the bond lengths and endocyclic bond angles [Formula: see text] in the eight imidazole rings of the title compound has provided an opportunity for investigating the effect of substitution on the geometry of the imidazole ring in a sample of 17 substituted imidazoles. While the bond lengths have been found at most weakly correlated, the multilinear correlations of the [Formula: see text] in this sample are highly significant. Among the substituents the NO2, group is the most ipso- [Formula: see text] -expanding and the anionic B (in the title compound) the most ipso- [Formula: see text] -contracting. Protonation or deprotonation at the N atoms affect the ipso C—N—C angles considerably. Limited comparisons are drawn with the results of the classical investigations by Domenicano et al. on the effect of substitution on the geometry of the benzene ring. Keywords: hydrogen bond, imidazole, lithium compounds, polymers, tetrahedral boron ions.

Beiträge zur Chemie des Phosphors, 109 [1] t-Bu6lAs2P6 - der erste Phosphor-Arsen-Polycyclus / Contributions to the Chemistry of Phosphorus, 109 [1] t-Bu6As2P6 - the First Phosphorus Arsenic Polycycle

The first phosphorus arsenic polycycle t-Bu6As2P6 (1) was synthesized by dehalogenation of a 3:1 mixture of tert-butyldichlorophosphane and phosphorus trichloride using magnesium. 1 has been characterized by spectroscopic methods and by a crystal structure analysis having the t-Bu6Ps-analogous 2,2′,3,3′,4,4′-hexa-tert-butyl-l′-diarsa-2,2′,3,3′,4,4′-hexaphospha- bicyclobutane structure. In solution, the rotation around the exocyclic As-As bond is restricted already at room temperature. 1 crystallizes triclinically in the space group PT (No. 2) with a = 919.4 pm, b = 924.3 pm, c = 1171.7 pm, a = 97.21°, β = 102.98°, γ = 112.75°, and Z = 1 formula unit (V = 0.8694 nm3, Dx = 1.295 Mg · m-3). The crystal structure has been solved by 'direct methods' and refined to R = 0.048 with 2131 observed reflections. The molecule with symmetry C1 consists of two trans oriented and slightly folded four-membered P3As rings. The exocyclic bond length (d(As-As) = 244.1 pm) as well as the average endocyclic bond lengths d̅(As-P) = 235.6 pm; 3d̅(P-P) = 222.6 pm) are normal. The arrangement of the tert-butyl substituents with average bond lengths d̅(P-C) = 189.9 pm and d̅(C-C) = 1 5 2 . 5 p m is all-trans.

The Molecular Structure of 2-Methyloxacyclobutane, as Studied by Electron Diffraction

A gas electron diffraction study of 2-methyloxacyclobutane has been carried out at room nozzle temperature. The four membered ring takes a planar conformation. The mean ra values for the O-C, C-C and C-H bonds are 1.448(5)A, 1.534(4)A and 1.118(3) Å, respectively. The endocyclic bond angles are C-C-C = 85.5(18)° and C-C-O=91.2 (15)°, while the angle C-O-C was assumed to be 92°. The position of exocyclic carbon atom was characterized, in addition by < Cexocyclic-C-O = 110.7(7)° and torsional angle Cexocyclic-C-O-C = 59.6(40)° (0° corresponds to the anti position of Cexocyclic-C and O-C bonds).