Volume 62, Issue 5

Chromium(II)tetrachloroaluminate can be prepared by reaction of chromium, chromium trichloride and aluminum trichloride in the molar ratio 1 : 1.94 : 5.79 or by reaction of stoichiometric amounts of chromium dichloride and aluminum trichloride. Sublimation of the compound yields phase-pure samples of colourless crystals. Cr(AlCl 4 ) 2 crystallizes in the non-centrosymmetric orthorhombic space group Pca2 1 (No. 29), a = 1511.38(3), b = 604.71(1), c = 1301.76(3) pm. The aggregation of Cr(AlCl 4 ) 2 molecules leads to a square-bipyramidal coordination of the chromium atom typical of high-spin d 4 ions due to the Jahn-Teller effect. The relationship to centrosymmetric Pd(AlCl 4 ) 2 (P2 1 /c) which is built up of similar molecules was established by means of a group-subgroup symmetry tree. The temperature dependence of the magnetic susceptibility agrees with Curie-Weiss behaviour (μ eff = 4.70 μ B ,Θ = −1.3 K).

The title compounds were synthesized from RE, REI 3 (RE = Ce, Gd, Y) and Al or Ga under an Ar atmosphere at 930 - 950 °C. The non-stoichiometric Ce 2+x I 2 Al 2+y and Ce 2 + x I 2 Ga 2+y compounds crystallize in the space group R3̄m (No. 166) with lattice constants a = 4.3645(3), c = 35.914(2) Å for the Al and a = 4.3009(2), c = 35.680(4) Å for the Ga compound. Excess electron density found in the Wyckoff position 3a could be due to a fractional occupation by Ce or M (x = 0.06, y = 0 or x = 0, y = 0.11 in the case of the Ga compound). The stoichiometric Gd 2 I 2 Ga 2 and Y 2 I 2 Ga 2 compounds crystallize in the space group P3̄m1 (No. 164) with lattice constants a = 4.1964(1) and 4.1786(7) Å , c = 11.4753(4) and 11.434(2) Å , respectively. Their structures feature M-centered (M = Al, Ga) RE trigonal prisms condensed via common rectangular faces. The electronic origin of the surplus of metal atoms in the octahedral voids between the I-layers of the Ce compounds was explored via extended Hückel-type calculations. Magnetic susceptibility, electrical resistivity and heat capacity measurements have also been carried out. These reveal a metal-insulator transition of Gd 2 I 2 Ga 2 at 40 K.

The series of magnesium compounds RE 4 RhMg (RE = Y, La-Nd, Sm, Gd-Tm, Lu) was prepared by high-frequency melting of the elements in sealed tantalum tubes. All samples were investigated by powder X-ray diffraction. The structures with RE = Sm, Gd, Dy, Ho, and Er as rare earth metal components were refined from single crystal diffractometer data: Gd 4 RhIn-type, F4̄3m, Z = 16, a = 1392.1(1) pm, wR2 = 0.060, 616 F 2 values, 19 variables for Sm 4 RhMg, a = 1380.8(2) pm, wR2 = 0.071, 530 F 2 values, 19 variables for Gd 4 RhMg, a = 1366.9(1) pm, wR2 = 0.070, 594 F2 values, 20 variables for Dy 4 RhMg, a = 1355.7(2) pm, wR2 = 0.077, 578 F 2 values, 20 variables for Ho 3.52 RhMg 1.48 , and a = 1355.4(2) pm, wR2 = 0.075, 559 F 2 values, 20 variables for Er 3.94 RhMg 1.06 .The rhodium atoms have slightly distorted trigonal prismatic rare earth coordination. Condensation of the RhRE 6 prisms leads to a three-dimensional network which leaves large voids that are filled by regular Mg 4 tetrahedra with a Mg-Mg distance of 312 pm in Sm 4 RhMg. The magnesium atoms have twelve nearest neighbors (3 Mg + 9 RE) in icosahedral coordination. In the structures with holmium and erbium, the RE1 positions which are not involved in the trigonal prismatic network exhibit RE1/Mg mixing. Shortest distances occur for Sm-Rh (286 pm) within the rigid three-dimensional network of condensed trigonal prisms.

Two modifications of CeCuSn were prepared from the elements: the high-temperature (β ) modification crystallizes directly from the quenched sample, while the low-temperature (α) modification is formed after annealing at 700 °C for one month. Both modifications were investigated by powder and single crystal X-ray diffraction. We find for β -CeCuSn the ZrBeSi-type structure, space group P6 3 /mmc, a = 458.2(1), c = 793.7(2) pm, wR2 = 0.0727, 148 F 2 values, 8 variable parameters. In the case of α-CeCuSn we find the NdPtSb-type structure, space group P6 3 mc, a = 458.4(1), c = 785.8(2) pm, wR2 = 0.0764, 233 F 2 values, 11 variable parameters. The copper and tin atoms build up layers of ordered [Cu3Sn3] hexagons. The layers are planar in β -CeCuSn, however, with highly anisotropic displacements of the copper and tin atoms. In α-CeCuSn a puckering effect is observed resulting in a decrease of the c lattice parameter. Both modifications of CeCuSn exhibit antiferromagnetic ordering, but there is a considerable difference in their magnetic behaviour. Anomalies in the physical properties of the α- and β -modifications of CeCuSn have been detected by Mössbauer spectroscopy and magnetic and specific heat measurements, which serve to explain the structure-property relations.

Red-orange, transparent single crystals of Yb 2 [CN 2 ] 3 [trigonal, R3̄c (no. 167), a = 630.02(3) and c = 2947.4(2) pm, Z = 6] are obtained by the reaction of Yb, Sn, Zn[CN 2 ] and NaN 3 in arc-welded Nb ampoules at 1100 K. The title compound exhibits characteristic C-N bond lengths and angles [d(C-N) = 122.7(3) pm and ∡(N-C-N) = 178.4(5)°, respectively] within the [N=C=N] 2 − unit as well as the expected fundamental frequencies in its optical spectra (Raman: νs = 1338; δ = 643 / 683 / 695 cm −1 ; IR: ν as = 2005 / 2037; δ = 640 / 679 cm −1 ). Since Yb 2 [CN 2 ] 3 adopts a corundum-type structure, Yb 3+ is octahedrally coordinated by six N atoms of different [CN 2 ] 2− anions [d(Yb-N) = 228.6(3) and 233.4(3) pm, 3× each] and every [CN 2 ] 2− group has four Yb 3+ as next neighbours which form a distorted tetrahedron.

By combination of TG/DSC and XRPD measurements it has been shown that zinc manganites form (Zn x Mn 3−x O 4 with 0.5 ≤ x ≤ 1.5) starting from mixtures of zinc oxalate dihydrate and manganese carbonate subjected to mechanical activation by high energy milling. Solid solutions ZnOMn 3 O 4 - ZnMn 2 O 4 are the products obtained by the same experimental conditions, when starting from a physical mixture. Furthermore milling, besides changing the enthalpy of dehydration of zinc oxalate, induces a partial formation of amorphous Mn 3 O 4 at r. t. In particular ZnMn 2 O 4 can be prepared by annealing the milled mixture for 18 h at 650 °C while a temperature > 1000 °C is needed to prepare ZnMn 2 O 4 from a physical mixture. Finally, the calorimetric data suggest that the mechanism of the reaction is different in the two kinds of mixtures.

Synthesis and characterization of the alkyne complexes [Co 2 (CO) 6 (L)], [W(CO)(L) 3 ] and [Pt(PPh 3 ) 2 (L)] with L = BnSC 2 SBn (Bn = benzyl) are described. X-Ray diffraction studies of [W(CO)(L) 3 ] and [Co 2 (CO) 5 (L)] 2 reveal that the donor ability of the sulfide group depends on the electronic and steric situation in the particular metal complex. The specific donor strength of sulfidesubstituted alkynes in their complexes is discussed considering the IR and NMR spectroscopic data.

Reactions of [(η 6 -C 6 Me 6 )RuCl 2 ] 2 and [(η 6 -p-cymene)RuCl 2 ] 2 with [Hg(ptpy) 2 ] (Hptpy = 2-pyridyl-m-toluene) in THF afforded [{(η 6 -C 6 Me 6 )Ru(ptpy)} 2 (μ-Hg 2 Cl 6 )] 1 and [(η 6 -pcymene) Ru(ptpy)(HgCl 3 )] 2, respectively. The crystal structures of complexes 1 and 2 have been determined by single-crystal X-ray diffraction. The ruthenium atom in both molecules 1 and 2 adopts a pseudo octahedral configuration containing a cyclometalated ptpy ligand. The Ru−C(ptpy) and Ru−N bond lengths in 1 are 2.049(3) and 2.089(2) Å, respectively. The corresponding bond lengths for 2 are 2.025(9) and 2.089(7) Å .

The complexes Ni(dmeds)(dmit), Ni(dmedt)(dmit), Ni(dpedt)(dsit), Ni(dpedt)(dmit), and Ni(dcdt)(dmit) (where dmeds is dimethylethylenediselenolate, dmedt is dimethylethylenedithiolate, dpedt is diphenylethylenedithiolate, dcdt is 1,2-bis-decylsulfanyl-ethene-1,2-dithiolate, dmit is 1,3-dithiol-2-thione-4,5-dithiolate, and dsit is 1,3-dithiol-2-thione-4,5-diselenolate) were prepared and characterized. The new complexes exhibit semiconducting behavior, with band gap values around 0.8 eV.

A kinetic and spectroscopic study was performed on the substitution of Fe(III) by Ni(II) in the water soluble anion [Fe(L 1− ) 2 L 2− ] − , a siderophore model (L − = dopa-semiquinone and L 2− = dopacatecholate). The reaction was followed in the UV/vis range through the appearing of an intense band at 592 nm due to the anion complex [Ni(L 1− )3] − formed which also presents a resonance Raman effect. The overall reaction obeyed a zero-order rate law at 25, 35, 45, and 50 °C, and the rate constants and thermodynamic parameters have been obtained. A chemometric study based on the Imbrie Q-type factor analysis revealed that the reaction occurred with only one kind of intermediate whose UV/vis spectrum has been calculated.

The synthesis, crystal structure and magnetic properties of [Mn(III)L(H 2 O) 2 ]+ClO 4 −, 1 [L = N,N′-bis(rac-3,5-dichlorosalicylidenato)-1,2-diaminopropane] are reported. Single crystal X-ray diffraction studies showed the structure to consist of [MnL(H 2 O) 2 ]+ octahedra, with trans-coordinated water molecules, which are linked into infinite helices by hydrogen bonds. The distorted octahedral manganese(III) centre contains an N 2 O 2 O′ 2 coordination sphere made up of the Schiff base ligand in the equatorial plane. In the axial direction, an elongation of the trans Mn-O water bonds to 2.165(2) and 2.187(2) Å is observed. Such elongations are typical of d 4 systems but in this case may also be attributed to the poorer donor power of the water molecules.

The charge density of the tripeptide L-alanyl-glycyl-L-alanine was determined from three X-ray data sets measured at different experimental setups and under different conditions. Two of the data sets were measured with synchrotron radiation (beamline F1 of Hasylab/DESY, Germany and beamline X10SA of SLS, Paul-Scherer-Institute, Switzerland) at temperatures around 100 K while a third data set was measured under home laboratory conditions (MoK α radiation) at a low temperature of 20 K. The multipole refinement strategy to derive the experimental charge density was the same in all cases, so that the obtained charge density properties could directly be compared. While the general analysis of the three data sets suggested a small preference for one of the synchrotron data sets (Hasylab F1), a comparison of topological and atomic properties gave in no case an indication for a preference of any of the three data sets. It follows that even the 4 h data set measured at the SLS performed equally well compared to the data sets of substantially longer exposure time.

Ethyl 5-oxo-3-(4-toluidino)-2,5-dihydro-4-isoxazolecarboxylate was prepared from the reaction of diethyl 2-(4-toluidinocarbothioyl)malonate with hydroxylamine. Its reaction with 2- chlorobenzoxazole gave the corresponding N-substituted isoxazolone. The structure of the final product 4 was confirmed by IR, 1 H and 13 C NMR spectroscopy and mass spectrometry, and by X-ray single crystal structure determination.

Treatment of 9,10-dibromoanthracene with one mole equivalent of n-butyllithium and chlorodiphenylphosphane yields 9-bromo-10-diphenylphosphanylanthracene (1). Oxidation of 1 with chalcogens leads to {Br(C14H8)(Ph2P=E)} with E = O (2), S (3) and Se (4). The syntheses and structure determinations of the parent compound 1 and the oxidized species 2 - 4 are reported.

Reactions of 2,4-dinitrophenylhydrazine with salicylaldehyde, pyridine-2-carbaldehyde and 2- aminobenzophenone in methanol result in the hydrazone Schiff base ligands salicylaldehyde-, pyridine- 2-carbaldehyde-, and 2-aminobenzophenone-2,4-dinitrophenylhydrazone, respectively. Crystals of salicylaldehyde-2,4-dinitrophenylhydrazone are monoclinic, space group P2 1 /c, a = 13.820(3), b = 4.3515(9), c = 25.159(7) Å , β = 123.01(2)° with Z = 4. The molecular packing is mostly a zigzag or herring-bone pattern.

An efficient method for the preparation of sulfonamidourea using triphosgene in organic solvents is reported.Sulfonylhydrazides and acetylsulfanilylhydrazide were transformed into the corresponding intermediates using triphosgene in 1,4-dioxane/water or tetrahydrofuran as solvents.These intermediates were converted in situ into symmetrical and unsymmetrical sulfonamidoureas in high yields and shorter periods of time related to previous methods.

X-Ray structure determinations of all three isomers of bis(bromomethyl)benzene and of two isomeric tetrakis(bromomethyl)benzenes show that the packing of the molecules is determined principally by interactions of the bromomethyl groups (C-H· · ·Br and Br· · ·Br), except for ortho-bis (bromomethyl)benzene, in which C-H· · ·π interactions play a major role.

Water has been used efficiently as a solvent for the reaction of barbituric acid, aldehyde and urea or thiourea to yield pyrimido[4,5-d]pyrimidines. This environmentally benign procedure leads to high yields of products of greater purity in a single step using water.

The compound 3,3′-[(4-hydroxy-3-methoxy-5-nitrophenyl)methylene]-bis(4-hydroxy-2H-1- benzopyran-2-one) (1) crystallizes in the monoclinic system, space group P2 1 /n, with cell constants a = 16.859(4), b = 6.1624(15), c = 25.164(4) Å , β = 98.019(19)°. The two 4-hydroxycoumarin fragments are intramolecularly hydrogen-bonded between hydroxyl and carbonyl groups. The pH-dependent color changes of 4-hydroxycoumarin derivatives were studied by means of potentiometric and spectrophotometric titration. On the basis of the results obtained, the use of 3,3′-[(4-hydroxy-3- methoxy-5-nitrophenyl)methylene]-bis(4-hydroxy-2H-1-benzopyran-2-one) as an indicator in alkalimetry and acidimetry is proposed.

Two diterpenes were isolated from the leaves of Xylopia langsdorffiana, the new ent-atisane- 7α,16α-diol named xylodiol (1) and the known 8 (17),12E,14-labdatrien-18-oic acid (2). The structures of these isolates were deduced by spectroscopic data interpretation. Compound 2was less toxic than xylodiol on V79 cells and hepatocytes.

Two new 27-nor-triterpene glycosides, pyrocincholic acid 3β -O-β -D-glucopyranosyl-(1→4)- β -D-quinovopyranosyl-28-O-β -D-glucopyranoside (Metatrichoside A, 1), pyrocincholic acid 3β -O-β -D-glucopyranosyl-(1→4)-β -D-quinovopyranosyl-28-O-β -D-glucopyranosyl-(1→6)-β -Dglucopyranoside (Metatrichoside B, 2), together with pyrocincholic acid 3β -O-β -D-quinovopyranosyl- 28-O-β -D-glucopyranoside (3), pyrocincholic acid 3β -O-β -D-quinovopyranosyl-28-O-β -Dglucopyranosyl-( 1→6)-β -D-glucopyranoside (4), quinovic acid 3β -O-β -D-quinovopyranoside (5), quinovic acid 3β -O-β -D-quinovopyranosyl-28-O-β -D-glucopyranoside (6), quinovic acid 3β -O- β -D-glucopyranoside (7) and quinovic acid 3β -O-β -D-glucopyranosyl-28-O-β -D-glucopyranoside (8) were isolated from the barks of Metadina trichotoma. Their structures were mainly determined by mass spectrometric and 1D and 2D NMR spectroscopic methods. Compound 5 and 6 showed cytotoxic activities towards the A549 non-small-cell lung cancer cell line (IC 50 = 8.43 and 6.06 μm), and the methanol extract inhibited the activity of cathepsin B with an IC 50 value of 0.77 μg mL −1 .

Two new iridoid glycosides, named lagotisoside D (1) and E (2), were isolated from Logatis yunnanensis. The structures of the two compounds were established as 6-O-α-L-(4″-O-E-3‴,4‴-dimethoxycinnamoyl) rhamnopyranosylcatalpol (1) and 6-O-α-L-(4″-O-Z-3‴,4‴-dimethoxycinnamoyl) rhamnopyranosylcatalpol (2) on the basis of spectral analysis.