Volume 62, Issue 10

The new ternary intermetallic compound Sr 14 [Al 4 ] 2 [Ge] 3 was synthesized from stoichiometric ratios of the elements. The crystal structure (trigonal, space group R3̅, a = 1196.58(2), c = 4010.33(7) pm, Z = 6, R1 = 0.0574) was determined using single crystal X-ray data. The structure contains two crystallographically independent tetrahedral [Al 4 ] anions with Al-Al distances in the range from 269.7 to 273.6 pm. Taking into account the Zintl concept and the isosteric analogy to white phosphorus, their formal charge is−8. Both of these tetrahedra are surrounded by 16 Sr cations. The three isolated Ge 4− anions per formula unit (isosteric to the noble gases) are coordinated by nine Sr cations. According to the ionic description Sr 14 [Al 4 ] 2 [Ge] 3 ̅↦14Sr 2+ +2[Al 4 ] 8− +3[Ge] 4− the title compound is an electron-precise Zintl phase. This interpretation is supported by the results of a FP-LAPW band structure calculation, which show a distinct minimum of the total density of states at the Fermi level. Attempts to synthesize the analogous compounds in the systems Sr-Ga-Ge and Ca-Ga-Ge resulted in the formation of new members of the Ca 11 Ga 7 structure type family. In the case of Ca-Al-Ge only the stable binary border compounds Ca 2 Ge and CaAl 2 were formed in respective experiments.

Stoichiometric hydrates of Li 3 VO 4 , the hexahydrate and two polymorphs of the octahydrate, were prepared by evaporation of alkaline aqueous solutions 1 molar in LiOH and 0.5 molar in the metavanadate LiVO 3 at r. t. with or without the addition of Lithium sulfide, i. e. at different pH values. Their crystal structures have been determined and refined using single crystal X-ray data; all lithium and hydrogen atom positions were localised and refined without contraints. All three title compounds crystallise in non-centrosymmetric space groups. The water molecules belong to the tetrahedral coordination spheres of the Li cations, i. e. they are embedded as water of coordination exclusively. The tetrahedral orthovanadate(V) anions VO 3− 4 and the LiO 4 tetrahedra are connected via common O corners to form building units which are further held together by strong, nearly linear hydrogen bonds. The hexahydrate Li 3 VO 4 ・ 6H 2 O (space group R3, a = 962.9(2), c = 869.2(2) pm, Z = 3, R1 = 0.0260) contains isolated orthovanadate(V) anions VO 3− 4 surrounded by a 3D network of cornersharing Li(H 2 O) 4 tetrahedra forming rings of three, seven and eight units. The water molecules are ‘isolated’ in the sense that no hydrogen bonds are formed between water molecules. The octahydrate is dimorphous: The triclinic polymorph of Li 3 VO 4 ・ 8H 2 O (space group P1, a = 592.6(2), b = 651.3(2), c = 730.2(4) pm, α = 89.09(2), β = 89.43(2), γ = 88.968(12)°, Z = 1, R1 = 0.0325) contains two types of chains of tetrahedra: One consists of corner-sharing Li(H 2 O) 4 tetrahedra only, the second one is formed by alternating LiO 4 and VO 4 tetrahedra, also sharing oxygen corners. Only one water molecule is ‘isolated’, the other seven form a branched fragment of a chain with hydrogen bonds between them. In the monoclinic form of Li 3 VO 4 ・8H 2 O (space group Pc, a = 732.6(1), b = 653.7(1), c = 1292.9(3) pm, β = 112.21(1)°, Z = 2, R1 = 0.0289) a fragment of a chain of three LiO 4 tetrahedra, two of which share a common edge, and one VO 4 tetrahedron represent the formular unit. These building blocks are connected via hydrogen bonds formed by three ‘isolated’ water molecules and a chain fragment of five connected water molecules.

Coppery-red, transparent single crystals of (Ba 6 N 5/6 ) 2 [NbN 4 ][CN 2 ] 6 (Im¯3, no. 204, a =1125.83(3) pm, Z = 2) are obtained by the reaction of Ba 2 N and ZnCN 2 with the container walls of the arc-welded Nb ampoules at 1100 K. The title compound assumes a stuffed skutterudite-type structure in which edge-sharing (Ba 6 N 5/6 ) octahedra form large voids which are occupied by either [NbN 4 ] tetrahedra or by [N=C=N] 2− units with symmetric C=N bond lengths of d = 121.8(6) pm but a bond angle deviating significantly from linearity (∡ (N-C-N) = 175.3(9)°). The IR spectra corroborate this crystallographic result by the fact that all fundamental vibrations are visible in the IR spectrum [ν 1 = 1262 (symmetric stretching mode); ν 2 = 1957/2009 (antisymmetric stretching mode); ν 3 = 611/633/653 cm −1 (bending modes)], which is symmetry forbidden for [N=C=N] 2− units having D ∞h symmetry but expected for the C 2v symmetry found in the title compound.

The syntheses of two functionalized xanthenes are described which after deprotonation represent ligands for dinuclear metal complexes. For the previously prepared [ R Xanthdim]H 2 - which after deprotonation leads to a ligand with two adjacent β -diiminato binding sites - a significantly improved synthetic procedure is described involving the Pd catalyzed coupling of two diethyl malonate moieties to the xanthene backbone. Deprotonation of the resulting compound [Xanthmal]H2 provides a ligand with two adjacent diethyl malonate functions. To demonstrate this, [Xanthmal]H 2 was reacted exemplarily with two equivalents of LDA to obtain the lithium salt {Li 2 [Xanthmal]}2 (4) which can be treated with ZnBr 2 to yield the zinc complex [Xanthmal] 2 Zn 2 (5). Alternatively, 5 can be obtained directly from [Xanthmal]H 2 , when ZnEt 2 is chosen as the metal precursor. The crystal structures of 4 and 5 are discussed. In summary, the results show that [Xanthmal] 2− is a suitable ligand for the preparation of novel dinuclear metal complexes.

The 1,3,2-diazaalumina-[3]ferrocenophane-ethyl(dimethyl)amine adduct 2, containing an Al-H function, reacts with terminal alkynes R-C≡C-H [R = n Bu (a), t Bu (b), Ph (c), SiMe 3 (d)] by elimination of H 2 to the amine adducts 4a - d containing an Al-C≡C-R function. Addition of pyridine leads to the corresponding pyridine adducts 5a - d, of which the molecular structure of 5d could be determined by single crystal X-ray diffraction. The formation of 4 is accompanied by side reactions such as trimerization of the alkynes to the 1,3,5-trisubstituted benzene derivatives 6a, c, and some polymerization of the alkynes. The solution-state structures of 4 and 5 were confirmed by multinuclear magnetic resonance spectroscopy ( 1 H, 13 C, 27 Al, 29 Si NMR). Structural features and molecular dynamics were investigated by appropriate 1 H/ 1 H NOE and magnetization transfer experiments, and particular attention was paid to the correct assignment of 13 C(Al-C≡C-R) NMR signals.

A new ternary mixed ligand dinuclear samarium(III) complex, Sm 2 (C 3 H 3 O 2 ) 6 (phen) 2 (1) (C 3 H 3 O 2 = acrylate; phen = 1,10-phenathroline), has been synthesized and characterized by microanalysis, IR and UV/vis spectra and single crystal X-ray diffraction. Compound 1 crystallizes in the triclinic space group P1̅ with cell parameters: a = 9.6687(19), b = 10.690(2), c = 10.799(2) Å , α = 105.50(3), β = 106.67(3), γ = 91.59(3)°, V = 1023.8(3) Å3. The Sm(III) cations are bridged by four acrylate anions into a dinuclear molecular unit. The nine-coordinate Sm(III) atoms adopt a significantly distorted monocapped anti-square-prismatic geometry. Within the crystal structure, the complex molecules are associated via π-π stacking interactions into one-dimensional supramolecular chains along the [011] direction. Compound 1 exhibits intense fluorescence in the solid state at room temperature.

The complexes Mn(Cl 3 CCOO) 2 (4,4′-bpy) (1) and [Cu 2 (ClCH 2 COO)(2,2′-bpy) 2 (OH)(H 2 O)]-(NO 3 ) 2 (2) (bpy = bipyridine) were generated under mild reaction conditions and characterized by IR spectra, thermogravimetric analysis (TGA), X-ray powder diffraction (XRD), and single crystal X-ray diffraction. Compound 1 exhibits a two-dimensional network with octahedrally coordinated Mn(II) atoms linked by 4,4′-bpy ligands and Cl 3 COO − ligands. Compound 2 features a supramolecular structure of binuclear complexes, with edge-sharing five-coordinated square-pyramidal units bridged by the ClCH 2 COO − ligand, an OH − group and a water molecule. Complex 1 crystallizes in the orthorhombic space group Pbcn with cell parameters: a = 16.5390(17), b = 11.6396(17), c = 9.9181(12) Å, V = 1909.3(4) Å 3 , Z = 4, wR2 = 0.1576. Complex 2 crystallizes in the triclinic space group P1̅ with cell parameters: a = 7.6190(15), b = 11.151(2), c = 16.640(3) Å , α = 73.13(3), β = 80.89(3), γ = 74.51(3)°, V = 1298.73(4) Å 3 , Z = 2, wR2 = 0.1265.

The adsorption behavior of benzoate, citrate, tartrate and glutamate on calcite dispersed in water was studied. At r. t. and pH = 9, the molar amount of substrate adsorbed decreases with increasing number of carboxylic groups in the molecule. Thus, monofunctional benzoate adsorbs in significantly higher molar amounts than trifunctional citrate. A more alkaline environment (pH = 12.5) has almost no effect on the adsorption behavior whereas a temperature increase, particularly from 40 to 60 °C, results in notably lower adsorbed amounts except for benzoate. Enthalpy changes determined by applying a modified Clausius-Clapeyron equation indicate a slightly exothermic benzoate adsorption process, whereas adsorption of citrate, tartrate and glutamate represents an endothermic, entropy-driven process. Zeta potential measurements conducted with highly concentrated CaCO 3 suspensions (water/CaCO 3 = 0.413) containing 0 - 100 mmol substrate/m 2 confirm that the adsorption of substrates with a higher number of carboxylic groups and a higher anionic charge results in a particularly negative surface charge on CaCO 3 .

The thermolabile triazenides M[tBu 3 SiNNNSiMetBu 2 ] (M = Li, Na) are accessible from the reaction of tBu 2 MeSiN 3 with the silanides MSitBu3 (M = Li, Na) at −78 °C in THF. At r. t. N 2 elimination from the triazenides M[tBu 3 SiNNNSiMetBu 2 ] (M = Li, Na) takes place with the formation of M[N(SiMetBu 2 )(SitBu 3 )] (M = Li, Na). X-Ray quality crystals of Li(THF)[N(SiMetBu 2 )(SitBu 3 )] (orthorhombic, Pna2 1 ) are obtained from a benzene solution at ambient temperature. In contrast to the structures of the unsolvated silanides MSitBu 3 (M = Li, Na), the THF adduct Li(THF) 3 SitBu 3 is monomeric in the solid state (orthorhombic, Pna2 1 ).

Two novel silver complexes with thianthrene (TA) as a ligand have been synthesized in the poorly coordinating solvent liquid sulfur dioxide, using silver salts with weakly coordinating anions [BF 4 ] − and [SbF 6 ] − . Both colorless compounds contain discrete molecular entities and SO 2 molecules included in the crystal structure. Selection of crystals and the diffraction data collection were performed at low temperatures (123 K). The tris(μ-thianthrene-κ 2 S)disilver(I) bis(hexafluoroantimonate) sulfur dioxide solvate [Ag 2 (TA) 3 ][SbF 6 ] 2 ·5SO 2 (1) (monoclinic, P2 1 /c, a = 21.644(3), b = 12.4216(4), c = 21.934(3) Å , β = 115.04(1)°, Z = 4) is made up of complexes bearing three TA units acting as bridging ligands with both S atoms towards two Ag + ions with d(Ag + -Ag + ) = 2.911 Å giving the [Ag 2 (TA) 3 ] 2+ unit approximately D 3h molecular symmetry. The bis(μ-thianthrene-κ 2 S)disilver(I) bis(tetrafluoroborate) sulfur dioxide solvate [Ag 2 (TA) 2 ][BF 4 ] 2 ・3SO 2 (2) (monoclinic, C2/c, a = 21.0045(6), b = 7.4553(2), c = 22.6024(6) A° , β = 109.65(0)°, Z = 4) is made up of [Ag 2 (TA) 2 ] 2+ units with two bridging TA units coordinating two Ag + ions with d(Ag + -Ag + ) = 2.925 Å giving the complexes approximately D2h molecular symmetry. Weak, secondary bonds between Ag+ and the F atoms of the anions, such as Ag···F-SbF 5 = 2.862(4) Å in 1 or Ag···F-BF 3 = 2.773(2) Å in 2, and with O atoms of SO 2 molecules link the complexes with the anions and the solvate molecules, respectively.

Generally, arylmethylene-cyanoacetic acid derivatives react with enols and aromatic or heteroaromatic hydroxy compounds to afford 2-amino-4H-pyran derivatives of type 6. In contrast, a ring closure with the nitrogen atom of the thiadiazole ring occurs when 2-phenacyl-1,3,4-thiadiazoles (1a - d) act on derivatives of arylmethylene-cyanoacetic acid giving rise to the formation of 7H- [1,3,4]thiazolo[3,2-a]pyridine derivatives 5a - r. The same products are obtained if 2-phenacyl-1,3,4- thiadiazoles react with aromatic or heteroaromatic aldehydes and cyanoacetic acid derivatives. The constitution of the novel compounds 5 has been confirmed by an X-ray analysis of 5a.

5-Oxo-10a-R-2,3,10,10a-tetrahydro-5H-[1,3]-oxazolo-[3,2-b]-isoquinoline-10-carboxylic acids [R = phenyl (trans-4), benzyl (trans-8, cis-8)] were prepared by reaction of homophthalic anhydride (2) and a corresponding 2-oxazoline. The configurations of trans-8 and cis-8 were assigned unequivocally based on the 2D-H-NOESY NMR spectra of the corresponding methyl esters. Compounds trans-4, trans-8 and cis-8 were converted in two steps with retention of the configuration to the target aminocarbonyl derivatives which are interesting from a pharmaceutical point of view. An important experimental correlation between the chemical shift of 10-H and the configuration of all compounds prepared was derived.

Two hybrids between the alkaloids bauerine C and rutaecarpine were prepared. Screening for cytotoxic activity revealed that introduction of two chlorine substituents to the quinazolinocarboline core of rutaecarpine strongly enhances cytotoxic activity, whereas methylation at the indole nitrogen is detrimental to activity.

An efficient, facile microwave-assisted synthesis has been developed for the preparation of unsymmetrical sulfide derivatives from 3-mercaptopropionic acid and a wide variety of alkyl, allyl or aryl chlorides or bromides. The synthesis performed in ethanol at 80 or 120 °C using sodium hydroxide as a base, selectively without an offensive smell, generates 3-(alkylthio)propionic acids in good yields. Effects of reaction components, temperature, and the heating technique on the formation of the product and side-products were studied.

The acetyl- and butyrylcholinesterase inhibiting natural product dictyophlebine 1 was subjected to different N-alkylation and hydrochlorination reactions by which five new and bioactive chemical derivatives (2 - 6) with pentyl, pent-4-en-1-yl, hex-5-en-1-yl, 4-chloropentyl and 5-chlorohexyl substituents at the 3-N position were obtained with high yield. The alkylated and chlorinated products 3 - 6 were found to have significantly higher inhibitory potential towards cholinesterase than the parent compound 1.

Two new benzopyran-4-one derivatives, applanatins A (1) and B (2), were isolated from the fruiting bodies of the fungus Ganoderma applanatum (Ganodermataceae), along with one known analogue, ganoderma aldehyde (3), as well as four known ganoderenic acids. The structures of the new compounds were elucidated on the basis of extensive spectroscopic analysis. The partial assignments of the NMR spectra of 3 were also revised.

The methanol-soluble part of Salvia nubicola has yielded a new germacranolide and a new ceramide named nubtrienolide and nubenamide, respectively. Structures of both the isolated constituents were elucidated with the aid of spectroscopic techniques; the nubtrienolide structure was further confirmed via single crystal X-ray diffraction analysis. Among both the metabolites, nubtrienolide showed strong growth inhibition against Pseudomonas aeruginosa while during phytotoxicity testing, the same compound promoted the growth of Lemna minor L. instead to inhibit it.

The reaction of dimethylcadmium with alcohols R-OH in equimolar ratio leads to the formation of tetrameric methylcadmium alkoxides with molecular formula [(MeCd)4 (OR) 4 ] [R = Me (1), Et (2) and i Pr (3)]. These compounds have been characterised by 1 H, 13 C NMR and IR spectroscopy, by mass spectrometry, elemental analyses and by X-ray crystallography (for 2 and 3). The solid state structures show distorted cubane-type aggregates with Cd 4 O 4 cores. The structural aspects and the spectroscopic characterisations of these compounds are discussed.