Volume 45, Issue 7

When ozone is passed through a solution of (PPh 4 ) 2 [As 2 Cl 8 ] in dichloromethane at –40 °C, first an instable red compound forms, then intense yellow PPh 4 [AsCl 6 ] is obtained. The latter can also be obtained by introducing chlorine instead of ozone. The crystal structure of PPh 4 [AsCl 6 ] was determined by X-ray diffraction (844 observed unique reflexions, R = 5,9%). Crystal data: tetragonal, space group P4/n, a = 1305.6(3), c = 752.2(4) pm, Z = 2. The structure is isotypic with that for other PPh 4 [MCl 6 ] compounds, the octahedral AsCl 6 - ions being situated on fourfold rotation axes and showing a well-known positional disorder in that they are somewhat tilted against the symmetry axes due to packing strain.

Single crystals of BeC 4 O 4 · 3 H 2 O were prepared from aqueous solution. The X-ray structure determination revealed a new coordination mode of the squarate dianion. C 4 O 4 2- is bound to Be 2+ by only one of its oxygen atoms. Three water molecules join the Be coordination sphere to form a slightly distorted tetrahedron together with the O squarate atom. Be-O squarate bond lengths are negligibly shorter than Be—OH 2 distances. Strong hydrogen bonds occur between water molecules and all Ο squarate atoms not bound to Be 2+ . These O squarate atoms act as proton acceptors in two hydrogen bonds, each of almost equal strength. One intramolecular hydrogen bond occurs within the BeC 4 O 4 .3 H 2 O moieties which are connected to each other by intermolecular hydrogen bonds. C 4 O 4 2- does not deviate markedly from planarity. Difference electron density maps show evidence for bent bonds in the C 4 ring system of C 4 O 4 2- .

Trimethylstannyl perrhenate, (CH 3 ) 3 SnOReO 3 (2), synthesized from dirheniumheptoxide and tetramethyltin, has a zigzag-chain crystal structure. This structure originates from catenation of individual molecules via the tin atom to a perrhenate group of another molecule. The tin atom thus forms the center of a trigonal-bipyramidal coordination geometry, with two oxygen atoms adopting apical positions while three methyl groups define the equatorial plane. The Re—O—Sn bonds alternate between linear and slightly bent. The zigzag-aggregation of the chain-structure results from the tetrahedral [ReO 4 ] subunits. Ionic contributions to the Re—O—Sn bonds are not evident from the structural data, nor do data obtained from solution indicate any ionization such as [(CH 3 ) 3 Sn] + [ReO 4 ]⁻. Following the synthesis of the title compound 2, the heavier congener triphenylplumbyl perrhenate (5) has been synthesized from Re 2 O 7 and Pb(C 6 H 5 ) 4 .

The isostructural title compounds have been characterized by X-ray powder and single crystal diffraction: R 3̅ c; Z = 6; a = 741.81(4), c = 1639.18(9) pm; 389 diffractometer data, R = 0.04, R w = 0.03 (K 3 CO 3 F); α = 776.1(3), c = 1741.2(9) pm; 235 diffractometer data, R = 0.07, R = 0.06 (Rb 3 CO 3 F). Both compounds are carbonate fluorides with isolated CO 3 2- and F - anions.

Crystals of Rh 2 Sb were prepared by sintering the elemental components in a NaCl/KCl flux. They crystallize in the orthorhombic space group Pnma with the lattice constants α = 572.1(1)-573.6(1) pm, b = 417.1(1)-418.1(1) pm, c = 792.8(2)-794.9(1) pm, V = 0.1892-0.1906 nm 3 for the antimony- and rhodium-rich side, respectively, of the homogeneity range at 800 °C. The structure belongs to the Co 2 Si-branch of the (anti-)PbCl 2 -type. It was refined from single-crystal diffractometer data to a residual R = 0.059. The crystal chemistry of the various PbCl 2 -type compounds is briefly reviewed.

Niobium pentabromide, NbBr 5 , is prepared in the orthorhombic ordered (α)-form from the elements in sealed quartz ampoules (Nb powder, Br 2 , l) at 973 K. The structure has been determined from single crystal data (a = 1288.8(2), b = 1869.0(3), c = 614.9(1) pm; Pnma (No. 62); Z = 8; R = 0.055). α-NbBr 5_ forms dimeric Nb 2 Br 10 molecules with d̄(Nb–Br b ) = 271.5 pm, d̄(Nb–Br e ) = 240.8 pm and d̄(Nb– Br a ) = 246.1 pm. α-NbBr 5 is a diamagnetic semiconductor with cgs χ mol dia (300 K) = –72 × 10 -6 cm 3 /mol. The band gaps of NbCl 5 , α-NbBr 5 and NbI 5 have been determined by diffuse reflection to be Eg(NbCl 5 ) = 2.74 eV, Eg(α-NbBr 5 ) = 1.99 eV, and E g (NbI 5 ) = 0.99 eV.

Dimeric 1,2-Dioxyphenylene-dichloride (1) crystallizes dimorphically. The already known monoclinic m-form (space group P21/α) is the thermodynamically stable modification and can be obtained by sublimation. The novel triclinic α-form (space group P1̄) is a metastable modification and can be obtained from CH 2 Cl 2 solution. The α-form crystallizes with a = 591.7(5) pm; b = 1457.0(8) pm; c = 991.7(6) pm; α = 96.68(3)°; β = 106.29(3)°; γ = 91.48(3)° and Z = 4 formula units (2 dimers). The molecules of the a- and the m-form are identical with respect to bond distances, bond angles and their conformations, but they are different in their spatial arrangement. The melting point of the α-form is 126.5 °C, of the m-form 140.0 °C. The melt of 1 solidifies as a glass from which the α-form recrystallizes.

Reaction of germanium powder and Cl 3 SiCH 2 Cl at 350 °C yields the l-germa-3-silapropane Cl 3 SiCH 2 GeCl 3 , and (Cl 3 SiCH 2 ) 2 GeCl 2 , in a “Direct Synthesis”. Cl 3 GeCH 2 CH 2 GeCl 3 is obtained from HGeCl 3 and C 2 H 2 as a “Hydrogermylation” product. Addition of CH 2 =CHSiCl 3 to HGeCl 3 yields the 1-germa-4-silabutane Cl 3 SiCH,CH 2 GeCl 3 , and Cl 3 GeCH 2 C(GeCl 3 )=CH 2 is obtained similarly from ClCH 2 C=CH and HGeCl 3 -NEt 3 . These Chlorogermanes or -germanes/silanes are converted into the corresponding germanes (silanes) by treatment with LiAlH 4 in tetralin as a solvent in the presence of triethyl(benzyl)ammonium chloride. The products are isolated in high yields and identified by standard analytical techniques, including 73 Ge NMR spectroscopy. Owing to their high volatility they are potential feed-stock gases for CVD experiments to generate a-GeC:H or a-Ge,Si,C:H materials.

The title compound has been prepared by the reaction of CrCl 3 with 15-crown-5 in acetonitrile suspension in the presence of water. It forms violet crystals, which are sparingly soluble in acetonitrile; they were characterized by their IR spectrum as well as by an X-ray structure determination. Space group P2 1 /c, Z = 4, 2902 observed unique reflexions, R = 0.029. Lattice dimensions at —70 °C: a = 1018.8(5), b = 780.0(4), c = 2097.1(10) pm, β = 93.21(3)°. [CrCl 3 (H 2 O)(15-crown-5)] has a molecular structure, in which the chromium atom is coordinated by three chlorine atoms, by the oxygen atom of the water molecule, and by two oxygen atoms of the crown ether molecule in a distorted octahedral fashion.

[{Cp(CO) 2 Fe} 2 SnCl 2 ] (1) reacts with (Me 3 Si) 2 Se to form the compounds [{Cp(CO) 2 Fe} 4 Sn 2 Se 2 ] (2) and [{Cp(CO) 2 Fe} 4 Sn 4 Se 6 ] (3). The structures of 2 and 3 were determined by X-ray structure analysis. 2 contains a four-membered Sn 2 Se 2 ring. In 3 an adamantane-like Sn 4 Se 6 cage is observed. The reaction of [{Cp(CO) 2 Fe} 2 SnCl 2 ] with (Me 3 Si) 2 S leads to [Cp 4 (CO) 7 Fe 4 Sn 3 S 4 ] (4) a compound with a tricyclic Sn 3 S 4 Fe cage.

Solutions of GaCl 3 in various ethers have been studied by 71 Ga NMR spectroscopy. σ 71 Ga data indicate that the predominant species in diethylether and tetrahydrofuran solutions are GaCl 3 · O(C 2 H 5 ) 2 and GaCl 3 . 2OC 4 H 8 , respectively. However, in monoglyme solution dissociation occurs and the product crystallizing from the solution is [cis-GaCl 2 (monoglyme)2]GaCl 4 as demonstrated by an X-ray structure determination of the solvate GaCl 3 · monoglyme.

Allyldiboran(4) derivatives la—c are obtained from allylmagnesium chloride and chloro derivatives of diboran(4). la—c are air-sensitive liquids; heating of le did not yield a 2,3-dihydro-l,2-diborole derivative (B). Reaction between 1,1-bis(dichloroboryl)-3,3-dimethyl-butane (5) and H 2 C=C(CH 2 SnMe 3 ) 2 (4) leads to the heat-sensitive chloro derivative 2a, in which the chlorine is substituted by Me 3 SiNMe 2 to give stable 1,3-bis-dimethylamino-5-methylene-2-neopentyl- 1,3-diborinane (2 b). 1,2-Bis(dichloroboryl)benzene and 4 yield the chloro derivative 3a, and its substitution with HN(i-Pr) 2 leads to 1,4-bis(diisopropylamino)-2,3-benzo-6-methylene-1,4,5,7-tetrahydro-1,4-diborepine (3 b). The X-ray structure analysis reveals a folded tetrahydro-1,4-diborepine ring.

18 nm Gold colloids are used as seeds for a controlled growth of 36 nm colloids which are then stabilized by P(m-C 6 H 4 SO 3 Na) 3 . These colloids can be isolated as golden leaflets and are readily soluble in water in virtually any concentration. Electron microscopic investigations prove a very small particle size distribution. X-ray powder diffraction and molecular weight determinations support the results of the electron microscopic investigations. The distance between the colloidal particles in two-dimensional layers corresponds to double-layers of phosphane ligands around each colloid, twice 1.2 nm. Isolated colloids seem to possess thicker ligand shells. A single 44 nm colloid shows a corona of about 7.2 nm thickness, corresponding to 12 phosphane layers. A quantitative description of two-dimensional packing densities is suggested using a novel theoretical model. By means of Monte Carlo simulations the two-dimensional structures are formed during the covering of supports of different geometry can be calculated.

The title compounds were obtained from NiS + PPh 4 Cl + HCl in dichloromethane, from NiCl 2 and PPh 4 Cl and from NiCl 2 + Na 2 S + 15-crown-5 in acetonitrile or CH 2 Cl 2 , respectively. Their crystal structures were determined by X-ray diffraction. (PPh 4 ) 2 [NiCl 4 ]: monoclinic, space group C 2/c, Z = 4, a = 1094.9(3), b = 1946.1(4), c = 2033.5(5) pm, β = 91.48(3)°; R = 0.07 for 2895 unique observed reflexions. [Na-15-crown-5] 2 [NiCl 4 ]: triclinic, space group P1̄, Z = 2, a = 987.6(1), b = 998.0(1), c = 1779.9(2) pm, α = 104.17(1), β = 95.43(1), γ = 109.95(1)°; R = 0.090 for 4155 unique observed reflexions. In both cases, the [NiCl 4 ] 2- ions have distorted tetrahedral structures. With PPh 4 + as the cation the distortion corresponds to a twisted tetrahedron which fulfils the point symmetry D 2 , the deviation from a flattened D 2d -tetrahedron being small. In (PPh 4 ) 2 [NiCl 4 ] cations and anions alternate in layers parallel to (001). In [Na-15-crown-5] 2 [NiCl 4 ] two of the Cl atoms of the anion are coordinated to sodium ions; one of the crown ether molecules shows positional disorder.

The reaction of CuSO 4 ·5 H 2 O with potassium 2-thiooxamate, K[NH 2 C(S)CO 2 ], yields [Cu(2-thiooxamate)2]·1.6 H 2 O. Crystal data: a = 1501.6(8), b = 1650(1), c = 375.4(2) pm, β = 90.65(5)°, Ζ = 4. The structure was refined with 2213 reflections to R = 0.044. Copper(II) is chelated by two thiooxamate ligands, which act as O- and S-donors forming five-membered chelate rings. This cis-planar [Cu(2-thiooxamate) 2 ] molecules are stacked. The axial coordination sites at copper(II) interact within the stacks with O- and S-donor atoms of neighbouring units. Above 60 K the magnetic susceptibility follows the Curie-Weiss law with antiferromagnetic coupling.

NMR experiments in solid caesium perbromate have recently been performed at magnetic fields of 1.88 T and 7.04 T together with spectral simulations for 79 Br, 81 Br and 133 Cs in solid caesium perbromate. The line shapes are dominated by quadrupole effects. For bromine the quadrupole asymmetry parameter [η] is observed to be zero at all temperatures while the quadrupole coupling constant (C Q ) as a function of temperature shows two approximately linear regions on either side of a non-linear region between 200 K and 260 K where an extended orientational phase transition occurs. 133 Cs shows an increase of C Q and a decrease of η with increasing temperature. This behaviour may be associated with an anisotropic change of the “a” lattice parameter.

31 P and 125 Te NMR data of trialkylphosphane tellurides are compared. The deviation of the shifts for Me 3 PTe and 'Bu 3 PTe from those of other phosphane tellurides is interpreted in terms of high s-character of the P–Te bond originating from the phosphorus (R = Me) and the tellurium (R = 'Bu) atom, respectively. The molecular structure of 'Pr 3 PTe has been determined by X-ray crystallography (P–Te 2.365 A). A reduction of the bond order is suggested based also on a comparison of the R 3 PSe and R 3 PTe NMR data.

Substitution of two chlorine atoms in 1,2-bis(dichloroboryl)ethane with diisopropylamine yields 1,2-bis(chlorodiisopropylaminoboryl)ethane (4), which is reacted with Na/K alloy to give 1,2-bis(diisopropylamino)-1,2-diboretane (5) in 91% yield. 5 crystallizes in the space group P 2 1 /c with the lattice constants a = 6.116(1), b = 16.658(5), c = 17.577(4) Å, β = 99.49(2)°.

Lithium poly(ketene-enolate) (1) was prepared from polyketene and LiOH. The resulting polymer salt was doped with varying amounts of iodine. The polymers show mixed ionic and electronic conductivity with a maximum at an iodine content of 47%.

Trialkyl phosphites (2a—c) react with 1,8-naphthosultam (6) to give the respective N-alkylated products 7 a—c. Compounds 7a—c were also prepared by the action of dialkyl phosphites on 6 in the presence of p-TsOH. Moreover, 7 a could be obtained by treating 6 with DMMP (8). On the other hand, chlorinated phosphorus reagents (11) condense with 6 to give products of type 12. Structures of the new products were assigned according to consistent analytical and spectroscopic measurements.

The second order-rate constants for the addition of water and ethanol to p-nitrophenyl isothiocyanate are larger in dimethyl sulphoxide solution than in pure water or ethanol. The detailed behaviour over a wide composition range suggests that H-bonding by the hydroxylic reactant to the solvent favours reaction, whereas H-bonding to this reactant retards reaction. The behaviour and relative reactivities of isocyanates and isothiocyanates suggest that protontransfer concurrent with nucleophilic attack at carbon, is less important in additions of hydroxylic compounds to isothiocyanates than to isocyanates. Branched-chain alcohols react more slowly with isothiocyanates than do primary alcohols. An excess of ethoxide ions reacts relatively rapidly with p-nitrophenyl isothiocyanate in ethanol to give the ionized thiourethane. The kinetics of this process, and the equilibrium constant for proton transfer between thiourethane and ethoxide ions, have been determined.

Cyclopropanated binaphthoquinones are obtained by addition of diazomethane to dimeric naphthoquinones and thermal or acidic degradation. 8,8′-dimethoxy-3′-methyl-2,3-dihydro-2,3-methano-2,2′-binaphthyldiquinone (9b) forms diastereomers by axial chirality and has a rotation barrier of about 20 kcal/mol.

1,4-Diaryl-2,3-dimethyl-1,4-diazabutadiene tin tetrachloride complexes 1 · SnCl 4 and 2 · SnCl 4 have been prepared and characterized by thermal properties, IR and Raman spectroscopy and mass spectrometry. A study on their behaviour in solvents with different donor ability by 1 H and 13 C NMR spectroscopy is also described.

Calculations (AM 1) on cis-pterocarpans are reported. The results are in agreement with experimental observations.

Attempted Mannich reaction with the title compound 1 using morpholine and formalin led to 2 or 4 according to the reaction conditions. Whereas, on using primary amines the diindeno [1,2-b:2′,1′-e]pyridine (9-11) were obtained, in addition to 2-methylene-1,3-indandione (6), in case of 10 and 11. However, the Mannich bases 13-15 were formed on treating 2-benzylidene-1,3-indandione with the appropriate secondary amine. The structures 2, 9-11 were confirmed via unambiguous syntheses.

Thermodynamic Data, Heterocyclic Seven-Membered Ring Compounds On heating in carbon tetrachloride or nitromethane the 5-methoxy-1-benzothiepines 1-4 isomerize to the corresponding thionaphtholes 5-8, whereas in cyclohexane from 1-4 the usual desulfuration products C arise. Kinetic and thermodynamic data have been estimated for the reactions 3 → 7 and 4 → 8. If the thermal rearrangement of 3 resp. 4 takes place in presence of cyclohexene sulphide, one gets the desulfuration products C also in carbon tetrachloride or nitromethane as solvent together with the equimolar amount of cyclohexene. This behaviour leads to the assumption of a S 2 -spezies as the primary elimination product of sulphur from the episulphide intermediate A.

Synthesis of the PCB derivatives 4-azido-2,2′,4′,5,5′-pentachlorobiphenyl and 4,4′-diazido-2,2′,5,5′-tetrachlorobiphenyl is described. The compounds are easily photoactivated by UV-C irradiation. Thus these derivatives are valuable photolabels which have been used already in studies of intracellular distribution.

A novel cyclic nitrone spin trap 5,5-dimethyl-3-(2-ethoxycarbonylethyl)-1-pyrroline N-oxide has been prepared and its ability to trap a series of transient free radicals has been investigated. This nitrone scavenges free radicals to give persistent nitroxides, e.g., the half life-times of hydroxyl radical adducts and tert-butoxy radical adducts in benzene >30 min, and the life-time of acetyl adducts >60 min. The EPR spectrum of 2,2-dimethyl-4-(3-hydroxypropyl)pyrrolidinyl-1-oxyl aminoxyl shows that the hyperfine splitting constants of two β-hydrogens are equal to 14.58 G and 23.29 G respectively, i.e., the two β-hydrogens are not magnetically equivalent. Radical addition to the nitrone is probably plane selective affording only one of the two possible geometric isomer pairs of the spin adduct nitroxides. The trans approach mechanism is proposed through configuration and conformation analysis.

Six S,S-dialkyl acetals 2a-f of inosose (1), tripodal in structure, have been synthesized, characterized and investigated by optical microscopy and differential scanning calorimetry (d.s.c.). The four S,S-acetals 2c-f with sufficiently long alkyl chains are thermotropic liquid crystalline; 2 e and 2 f are even dithermomesomorphic. Each of these four inosose derivatives 2c-f exhibits monotropically a most likely cubic mesophase (M I ); in addition 2e and 2f show enantiotropically a hexagonal mesophase (H x ) with a non-covalent, supramolecular H-bridge architecture. Whereas the nature of the optically isotropic mesophase M I needs further clarification the stable high temperature mesophase H x of 2 e and 2 f has been established by a miscibility test using a sugar S,S-dialkyl acetal also tripodal in structure and with a H x phase proved by X-ray diffraction, but in contrast to 2 with an acyclic hydrophilic part. Similarities of structural features between the H x -phases of 2e and 2f as well as of other thermotropic and lyotropic liquid crystal systems are discussed briefly.

Solid/liquid phase transfer catalytic conversions of KSCN and benzyl chloride at 180 °C give thiocyanate/isothiocyanate ratios depending on catalyst structure. Liquid/liquid PTC at 100 °C yields thiocyanate exclusively.

From the reaction mixture of Mn(III) acetate and several tripod-like ligands, a Mn(II) complex, a binuclear Mn(III) complex with (μ-oxo)(μ-acetato) core, and a Mn(III)–Mn(IV) complex with a di-μ-oxo bridge were obtained. This demonstrates that the oxidation state of the manganese ion in these compounds is drastically affected by small changes in ligand character.

The crystal structure of (AsPh 4 ) 2 [Re 3 Cl„(H 2 O)]·H 2 O, previously thought to be (AsPh 4 )2[Re 3 Cl 11 ], was redetermined from single-crystal four-circle diffractometer data. The crystal system is triclinic, PĪ, a = 983.1(6), b = 1200.5(6), c = 2566.2(10) pm, α = 92.67(4), β = 99.95(4), γ = 113.38(2)°, V m = 817.95(1) cm 3 /mol, R = 0.043,R w = 0.033.

A new eudesmanolide has been isolated from Cadaba farinosa. Its structure was determined by spectroscopic studies including 2 D-NMR (J-resolved, COSY-45 and hetero COSY experiments).

Dark red single crystals of Re 3 Cl 6 (Acac) 3 are obtained from a solution of “ReCl 3 ·2H 2 O” in acetylacetone by slow evaporation. The unit cell (monoclinic, P2 1 /c, a = 1687.3(9), b = 963.4(5), c = 1664.3(9) pm, β = 108.97(4)°) contains four molecules of Re 3 Cl 6 (Acac) 3 . Each of the bidentate Acac(—) ligands substitutes one of the in-plane terminal and one of the out-of-plane terminal ligands with respect to the Re 3 triangle.

The twelve possible chlorinated benzenes and the three isomeric monochlorobiphenyls are electrochemically reduced in a divided cell in methanol at a lead cathode. Chlorobenzene and benzene or biphenyl, respectively, are formed with acceptable current yields and very good chemical yields.

Three equivalents of the ether-phosphane ligands 2a-c react with Cl 2 Ru(PPh 3 ) 3 (1) to give the complexes trans-Cl 2 Ru(P ̑O)(P∼O) 2 (3a-c) (P∼O = η 1 -P-coordinated; P ̑O = η 2 -Ο,Ρ-coordinated). The hemilabile character of the P,O–ligands is becoming evident by the fluxional behaviour of 3 a-c. The coalescence temperatures in the AB part of their 31 P{ 1 H} NMR spectra are found at -10, 15 and -15 °C (AG* = 48, 53 and 47 kJ/mol). Because of steric effects, 3 a, in which the ether oxygen atom has the lowest basicity, and 3c, with the smallest ether substituent, show nearly the same dynamic properties.

3β,21 α-dihydroxy-oleane-11,13-dien-28-oic acid was isolated from the roots of Glycyrrhiza echinata L. and its structure was elucidated by spectral analysis.