Volume 38, Issue 12

The reaction of 2,2′-dipyridil with iodine (I 2 ; molar ratio 1:3) in CH 2 Cl 2 solution yields the polymeric complex 2,2′-dipyridil(I 2 ) 3 . The crystal structure of the compound was determined from single crystal X-ray data (monoclinic, C2/c, a = 3215.0(16), b = 439.9(1), c = 1824.1(9) pm, β = 130.79(3)°, Z = 4). 2,2′-Dipyridil(I 2 ) 3 forms infinite chains of alternating I 6 units and bifunctional dipyridil molecules

Al 2 Sb 2 I 12 (1) was prepared by heating stoichiometric amounts of AlI 3 and SbI 3 in CS 2 . The crystal structure of 1 was determined from single crystal X-ray data. The compound crystallizes in the monoclinic space group C2/m with a = 1644.0(3), b = 1318.3(2), c = 728.9(1) pm, β = 119.33(1)°, and Z = 2. The structure was refined by least squares methods to a final unweighted R value of 0.064 for 676 nonequivalent reflections. The structure is built up of Al 2 Sb 2 I 12 units in which two Sb-I octahedra share four common edges with two Al-I tetrahedra. As a consequence of the stereochemical activity of the non-bonding electron pair of antimony these cations are displaced from the centers of the iodine octahedra so that three different Sb-I bonds with distances of 270.8, 312.3, and 358.9 pm are observed in 1. The structure of Al 2 Sb 2 I 12 can also be derived from the layer structures of the BiI 3 type

Using 293 K diffractometer intensity data the structure of [Na(H 2 O) 3 ] 2 TeBr 6 has been determined by single crystal X-ray technique and refined to a final R w of 0.048. The crystals are monoclinic (space group C2/m) with a = 13.039(4) Å, b = 10.899(8) Å, c = 6.838(3) Å, β = 115.89(2)° and Z = 2. The structure contains infinite chains parallel [001] built up by face-sharing Na(H 2 O) 6 -octahedra. Isolated TeBr 6 2- octahedra between these chains represent the anion part of the structure, which can be regarded as a packing of layers based on a 3 3 .4 2 .-net consisting of oxygen and bromine atoms

Low temperature X-ray structural analyses of monoclinic single crystals of S 10 and S 6 · Si 10 (prepared from the components) show that the cyclic S 10 molecule exhibits the same D 2 conformation in both compounds with bond distances between 203.3 and 208.0 pm, bond angles (α) between 103 and 111°, and torsional angles (τ) between 73 and 124°. The S 6 molecule (site symmetry C i ) in S 6 · S 10 is very similar to the one in pure S 6 (d SS = 206.2 pm, α= 103°, τ = 74°). All intermolecular interactions are of van-der-Waals type. The Raman spectrum of S 6 · S 10 can be explained by a superposition of the S 6 and S 10 spectra

Fluorosilylphosphanes of the type R 2 SiFPHR′ (R = CHMe 2 , CMe 3 , NMeSiMe 3 ; R′ = H, C 6 H 5 ; 1-4) are obtained in the reaction of difluorosilanes with lithiated phosphanes in a molar ratio 1:1. Diphosphasilanes (5, 6) and a difluorosilylphosphane (7) are isolated as by-products. 1-4 react with n-C 4 H 9 Li to give cyclic silylphosphanes, LiF, and C 4 H 10 (8-11). Dilithiated 5 reacts with F 2 PN(CMe 3 )SiMe 3 to form of a four-membered SiP 3 -ring 12. The 31 P NMR spectra of 9 and 11 show signal coalescence for the cis-and trans-isomers at room temperature. The crystal structure of the cis-isomer of 11 has been determined. The substituted ring 13 is prepared in the reaction of lithiated 9 and Me 2 SiF 2

The preparation of S 4 N 5 F by fluoride ion addition to the S 4 N 5 + -cation in liquid SO 2 is described. The structure of the fluoride was determined from single crystal data. The mechanism for the formation of S 4 N 5 F and the stability of possible isomers is discussed on the basis of MNDO/1 calculations

5-Bromo-uracil (1) reacts with sodium diphenylphosphide or a mixture of sodium diphenylphosphide and sodium amide in liquid ammonia to give sodium 5-bromo-uracilate (5 a). From water 5 a crystallizes with one mole H 2 O yielding 5b. Treatment of 5 a with D 2 O yields sodium 5-bromo-N-deutero-uracilate-D 2 O (1/1) (5 c). With chlorodiphenyl-phosphine 5 a forms 1-diphenylphosphino-uracil (2). 5 a, b, c show N(1) · N(3)-(H/D)-tautomerism in concentrated D 2 O solutions already, but in DMSO or D 6 -DMSO only in dilute solutions. All the compounds were characterized by infrared, Raman, 1 H NMR, UV spectra and conductometry

Tl 2 P 2 S 6 crystallizes in the orthorhombic system, space group Immm, Z = 2 with the lattice constants a = 793.2(4) pm, b = 689.2(4) pm, c = 901.9(5) pm. In the structure there are discrete P 2 S 6 2- -anions. The P 2 S 6 2- -ion was found to be a hexa-thiometadiphosphate group where the two P atoms are linked by two S bridges. Far infrared, infrared and Raman spectra of this compound have been recorded. The observed frequencies are assigned on the basis of P 2 S 6 2- units with D 2h symmetry in analogy to the isoelectronic Al 2 Cl 6

The new compound Ba 4 Ga 4 S 10 crystallizes in the monoclinic system, space group C2/c with the lattice constants: a = 1529.4(7) pm, b = 1479.3(7) pm, c = 858.0(5) pm, β = 106.04(5)°. In the structure there are adamantanelike Ga 4 S 10 8- anions, isosteric to the neutral P 4 S 10 molecules. The Ba 2+ ions are coordinated by 7 S atoms

A series of alkali metal thiocarboxylates (1-5) were found to be readily obtained in high yields by the reaction of thiocarboxylic acids with metal hydrides (LiH, NaH, KH), and rubidium or caesium acetates, respectively. Their physical properties were disclosed

13 C and 15 N photo-CIDNP effects were determined for the reversible electron transfer from pyrene to arene diazonium salts on excitation of the charge transfer band at 360 nm. The diazonium salts being the products of back electron transfer (“cage products”) show enhanced absorption for 13 C(1) and the 15 N-enriched diazonium group, whereas the escape products, ArH or 15 N 2 , respectively, yield emission signals. It was shown that the intensities of the CIDNP effects depend on the rates of intersystem crossing k isc within the geminate radical pair, i.e. on the magnetic nucleus used as a probe of the CIDNP effect. Using 1 H, 13 C or 15 N the time domain of observation can be manipulated in the ranges of 90-100 ns, 15-20 ns and 3-5 ns, respectively. Furthermore, the CIDNP intensities depend on the proper balance of the rate of electron back transfer, k -e , and the rate k p of formation of the escape product. Since k -e increases with increasing energy of the geminate radical pair, this balance and therefore the CIDNP intensities vary according to the substituent present and the electron donor used

Single crystals of trans-L 2 Mo(CO) 4 (L = 1,3-dimethyl-4-imidazolin-2-ylidene) transform to crystals of cis-L 2 Mo(CO) 4 upon heating to 133 °C. X-ray analyses demonstrate that the lattice transformation accompanying the molecular isomerization process is of the martensitic type. Morphological studies reveal that phase boundaries move parallel to close packed planes. The interrelation between lattice movements and intramolecular reorientations is analyzed

2,2′-Bipyridinium pentachloroantimonate (III) and the metastable modification of 4,4′-bipyridinium pentachloroantimonate(III) were synthezised and investigated by single crystal X-ray diffraction analysis. The structures consist of 2,2′-bipyridinium and 4,4′-bipyridinium cations, respectively, and of pentachloroantimonate anions. With regard to bonding and short intermolecular contacts the coordination of the Sb atoms is distorted octahedral in both structures. Bond lengths of equivalent Sb-Cl bonds differ strongly within the structure of the 2,2′-bipyridinium salt (239.9 pm to 312.1 pm) and are not distinguishable from short intermolecular contacts (305.4 pm and 321.8 pm). In the structure of the 4,4′-bipyridinium salt, bond distances vary only from 240.9 pm to 267.8 pm and are clearly below intermolecular contacts at 318.2 pm. In spite of the different distances the total bond order for each Sb atom is 3. In the structure of the 2,2′-bipyridinium salt the anions build tetramers, whereas in the structure of the 4,4′-bipyridinium salt the anions form chains

The γ-radiolysis of N 2 O-saturated aqueous solutions generates OH radicals and a small amount of H atoms. In 1,3-dimethyluracil solutions (10 -3 M) these radicals add mainly to the 5-position of the C(5) -C(6) double bond of the solute. The resulting products have been identified by GC-MS after trimethylsilylation. The major products (G values in brackets) are dimers of the C(5) OH-adduct radicals (3.4), 5,6-dihydro-5,6-dihydroxy-1,3-dimethyl- uracil (0.85), 5,6-dihydro-5-hydroxy-1,3-dimethyluracil (0.75), dimer of the C(5)-OH- adduct with the C(5)-H-adduct radical (0.2) and 5,6-dihydro-6-hydroxy-1,3-dimethyl- uracil (0.2). G( 1,3-dimethyluracil consumption) has been found to be 5.7. The major reaction in this system is the dimerisation of the primary radicals. To a small extent the primary radicals also disproportionate by electron transfer to give the glycol 5,6-dihydro-5,6-dihydroxy-1,3-dimethyluracil as one of the products. Radiolytically formed H 2 O 2 which could oxidise the C(5)-OH-adduct radical does not contribute to the formation of the glycol because the H 2 O 2 yield is not reduced with respect to its expected “molecular yield” (G = 0.75). In contrast to the uracil system where it has been reported that drastic changes in radiolytic yields occur on going from neutral to alkaline irradiation conditions no such changes have been observed with 1,3-dimethyluracil. However, an acid-catalysed rearrangement from the C(5)-OH-adduct to the C(6)-OH-adduct radical is observed in the present system

In the spinel system FeV 2 O 4 -ZnV 2 O 4 pure Fe(II)-spinels could not be prepared. Mössbauer spectra show that the solid solution has the composition Fe x 2+ Zn 1-x :[Fe y 3+ V 2-y ]O 4 , y depending on the partial pressure of oxygen during preparation. The reaction of 1/3 Fe + 1/3 Fe 2 O 3 + V 2 O 3 in a closed tube was also studied by X-ray and Mössbauer investigation

The walk rearrangement of cyclopentadienylphosphanes and related compounds is analyzed on the basis of a quantum chemical study. Although according to orbital symmetry considerations the reaction takes place with retention of configuration (at the migrating atom), inversion of configuration is also feasible. Low energy barriers for the walk reaction are expected if (a) radical stabilizing groups are attached to the cyclopentadienyl unit, (b) the fragment MR 2 (migrating group) exerts strong radical stabilizing ability and (c) possesses energetically high lying frontier orbitals. The final goal, the device of a molecular structure which freezes in the transition state structure is discussed

Steady-state γ-radiolysis of 5 × 10 -4 M pyrimidine and purine 2′-deoxyribonucleosides in aqueous solutions saturated with N 2 , N 2 O and O 2 , respectively, have been carried out in the presence of 0.1 M KBr. The main final degradation products have been isolated and characterised by various spectroscopic measurements including 1 H and 13 C NMR, UV, C.D. and mass spectrometry. The radiation-induced decomposition of thymidine is mostly accounted for by an ionic mechanism involving Br 2 , the decay product of Br 2 -·, as the reactive oxidising specie. On the other hand the degradation of the purine ring of 2′-deoxy-adenosine and 2′-deoxyguanosine may be accounted for by the action of Br 2 -·or Br 3 ·2-

Reactions of the cyclic systems (NPCl 2 ) 2 NSOX and NPCl 2 (NSOX) 2 (X = F, Cl, Ph) with NH 3 in diethyl ether or acetonitrile at low temperature provide convincing evidence that the P-bonded chlorine atoms are replaced by NH 2 groups along a geminal pathway. No disruption of the S-F and S-Ph bonds occurs. Aminolysis of NPCl 2 (NSOCl) 2 proceeds to NP(NH 2 ) 2 (NSOCl) 2 , followed by decomposition, (NPCl 2 ) 2 NSOCl can be transformed to NPClNH 2 NP(NH 2 ) 2 NSOCl without cleavage of the ring skeleton

UV photoelectron spectra of the title compounds are reported. Assignments based on He(I)/He(II) intensity differences, shift effects, and comparison with related molecules allow an assignment of the upper valence bands. Electronic differences between nickel and both platinum and palladium are reflected in the spectra, especially with respect to bands due to ionization of electrons from the metal. Strong evidence is found for π interaction of the ligand phenyl system with metal orbitals

The title compound 7 is prepared in a five-step synthesis starting from 1,2-di-O-acetyl-5-O-benzoyl-3-deoxy-3-O-(diethoxyphosphonomethyl)-β-D-ribofuranose (2). The preferred conformation of 7 is derived from its 1 H and 13 C NMR data

Carboxylic esters have been prepared from 5-alkyl-2-thiophenecarboxylic acid and hydrochinone, biphenol, respectively cholesterol as well as one ester from 2,5-thiophene dicarboxylic acid and p-ethylphenol. Only the esters from biphenol respectively cholesterol have liquid crystalline phases

According to a GC-MS analysis of methylated extracts the abdominal tips of the water beetle Laccophilus minutus (Dytiscidae) contain four β-hydroxyalkanoic acids. On the basis of MS and GC data another compound was assigned the structure of 6-octenoic acid. The same β-hydroxyalkanoic acids, and in addition, traces of β-hydroxyheptanoic acids were identified in dissected pygidial defensive glands after trimethylsilylation. Methyl 3,4-dihydroxyphenylacetate was recognized as a further main component in the pygidial gland secretion from the mass spectrum of its TMSi ether. The Laccophilinae occupy unique position among all the dytiscide subfamilies because they are the only water beetles which store β-hydroxyalkanoic acids in their pygidial glands. On the other hand the dytiscides appear to form a monophyletic group which is supported by the occurrence of methyl 3,4-dihydroxyphenylacetate. This class of compound is also commonly encountered in the other dytiscide subfamilies

2-Mercapto-4-amino-5-cyano-6-arylpyrimidines (1a, b), 2-hydroxy derivatives 1c, d and 2-methylmercapto derivatives 4 a, b were synthesised via the reaction of either a mixture of malononitrile and aromatic aldehyde or arylidene malononitrile with thiourea, urea and S-methylisothiourea, respectively. 1c, d could also be obtained by the action of hydrogen peroxide on 1a, b or by the action of hydrochloric acid on 4a, b. Compounds 4a, b could also be prepared by the action of methyl iodide on 1a, b. 4a reacted with hydrazine hydrate to give the 2-hydrazino derivative 5 which condensed easily with aromatic aldehydes to give the Schiff’s bases 6 a, b. Compound 5 could be converted into the tetrazolo-and s-triazolopyrimidines 7 and 9 by the action of nitrous acid and carbon disulphide respectively. Structures of the newly synthesised compounds were established by chemical routes and spectral studies

Both visnaginone and khellinone react with malononitrile, ethyl cyanoacetate or cyanoacetamide in presence of ammonium acetate to give substituted furobenzopyrans or furobenzopyridones. However, the reaction of visnaginone and khellinone with aldehydes, and malononitrile in presence of ammonium acetate leads to the formation of the corresponding 2-amino-4,6-disubstituted pyridine 3-carbonitriles. The latter compounds are also obtained by treating the respective chalcones with malononitrile and ammonium acetate. 3-Substituted 1,3-diketobutyrates form with malononitrile or with cyanoacetamide and ammonium acetate the 2-amino-4,6-disubstituted pyridine-3-carbonitriles or the 4,6-di-substituted cyanopyridones, respectively

The reaction of 1,1,2,2-tetra-tert-butyl-1,2- dihalodisilanes with alkali metals or metal naphthalenides leads to a complex reaction mixture from which one compound has been identified by its GC/mass spectrum as tetra-tert-butyldisilene (1). The constitution of 1 has been further confirmed by its cycloaddition products with benzil or 1,3-cyclohexadiene, respectively

Different catalysts were investigated with respect to their C-Cl-hydrogenolysis activity in perchloro compounds. C-Cl-hydrogenolysis to the parent hydrocarbon proceeds in the gas phase with a Pd/SiO 2 catalyst in the presence of H 2 at a temperature of 330 °C

A new indoline alkaloid, mehranine, has been isolated from the leaves of Ervatamia coronaria to which structure 1 has been assigned