Volume 40, Issue 6

The new compound Gd 2 NCl 3 is formed from GdCl 3 with Gd and N 2 as well as from GdCl 3 with GdN (at 1020 K). The crystal structure contains NGd 4 tetrahedra, which are linked via opposite edges to form infinite chains (Orthorhombic, Pbcn; a = 1301.7(1), b = 673.10(6), c = 614.03(7) pm; R = 0.031 for 578 independent reflections). The formal analogy with structures containing condensed clusters, e.g. Gd 2 Cl 3 , is discussed.

The new compounds Gd 2 C 2 Br 2 , Gd 2 Br 2 and Gd 6 C 2 Br 7 are formed from GdBr 3 with Gd and carbon at 1170 to 1320 K. The crystal structures contain condensed Gd octahedra, which are filled with either C 2 -groups or carbon atoms. (Gd 2 C 2 Br 2 : monoclinic, C2/m; a = 702.5(2), b = 383.61(9), c = 986.8(3) pm; β = 94.47(2)°; R = 0.063 for 330 independent reflections. Gd 2 CBr 2 : trigonal, twinned, P3 ml; a = 382.09(7), c = 982.4(4) pm; R = 0.074 with 123 independent reflections.

The crystal and molecular structure of Ph 2 Si(NMeBMe) 2 NMe (1) and MeB(NMeSiPh 2 ) 2 NMe (2) have been determined by X-ray structure analyses. Both compounds possess almost planar heterocycles. The average BN bond lengths in both compounds are practically identical (1.44 Å), but the two nonequivalent SiN bonds in 2 are significantly different (1.719, 1.732 Å). NMR data ( 1 H, 11 B, 13 C, 27 Si) are consistent with planar silaborazine rings.

By reaction of COS with malonitrile in presence of potassium ethanolate in ethanol K 2 O(S)CC(CN) 2 · H 2 O is obtained. It reacts with Ba(NCS)2 ·3H 2 O in ethanol to form colourless crystals of BaO(S)CC(CN) 2 · 4H 2 O. The space group of the barium salt is Pn2 1 a (standard: Pna2 1 ) with Z = 4. The structure consists of Ba 2+ and [O(S)CC(CN) 2 ] 2 - ions. The barium ion is bound to three nitrogen and six oxygen atoms. The coordination polyhedron is a tricapped trigonal prism. The anion [O(S)CC(CN) 2 ] 2 - is not exactly planar and is involved in several hydrogen bondings.

Single crystals of KSc 2 F 7 have been prepared from a mixture of KF and ScF 3 . The samples were investigated by X-ray methods. KSc 2 F 7 crystallizes orthorhombically with a = 10.643(2), b = 6.540(1), c = 4.030(1) Å. These data indicate a close crystallographic connection to the monoclinic unit cell of KIn 2 F 7 [1], But in contrast to KIn 2 F 7 , KSc 2 F 7 crystallizes in space group No. 65. Cmmm - D 19 2h . The R-value for 341 observed independent reflections is 0.060.

Hafnium Hexathiohypodiphosphate, Crystal Structure HfP 2 S 6 is prepared from the elements at temperatures between 500 and 900 °C. The single crystal X-ray analysis reveals isotypism (Fdd2, a = 1100.7(3), b = 747.6(2), c = 2200.8(4) pm) with TiP 2 S 6 .

The compound KLiS has been prepared and its crystal structure is determined by X-ray diffraction techniques. The hygroscopic, yellow compound crystallizes in the tetragonal space group P4/nmm (Z = 2) with the cell parameters a - 431.79(4), c = 696.20(9) pm. The structure was solved from 2100 counter reflections (356 symmetry independent reflections) through a Patterson synthesis and refinement by Fourier syntheses to a least squares residue of 0.026. The structure is characterized by c-centered squares of lithium layers interspersed by anti-parallel ordered K-S-pairs forming an anti-PbFCl-type geometry.

The reaction of N,N-dichlorophenylsulphonamide with tungsten hexacarbonyl in refluxing CCl 4 leads in good yield to the yellow polymeric complex [(PhSO 2 N) 2 WCl 2 ] x , which may be converted to the octahedral nitrene complex [(PhSO 2 N) 2 WCl 2 (CH 3 CN) 2 ] by recrystallisation from aceto­nitrile. Crystals of the acetonitrile complex are triclinic, space group P 1̅, a = 820.7(2), b = 1128.8(3), c = 1286.9(3) pm, α = 89.25(3), β = 89.54(3). γ = 72.67(2)°, Z = 2, R = 0.027 for 2527 unique observed reflections.

The synthesis of [Ph 4 As + ] 2 [Cl 4 Re(NS)(NSCl) 2- ] · CH 2 Cl 2 (4) from the reaction of S 4 N 4 , Cl 4 ReN, and Ph 4 AsCl is reported. CH 2 Cl 2 is used as solvent. The reaction of S 4 N 4 with Re 2 Cl 10 similarly leads to the salt [Ph 4 As + ][Cl 2 ReNS - ] (5) in a smaller yield. 4 crystallizes in the triclinic space group P1̅ with Z = 2, a - 10.434(2), b = 12.1454(6), c = 21.125(2) Å, a = 81.210(6), β = 86.70(1), γ = 76.624(8)°.

The mixed chloro-bromo complexes [IrCl n Br 6-n ] 2- and [IrCl n Br 6-n ] 3- , n = 1 - 5. were separated by ion exchange chromatography on diethylaminoethylcellulose. Due to the stronger trans-effect of Br compared with Cl, on treatment of [IrBr 6 ] 2- 3- with Cl - nearly pure cis/fac-isomers and by reaction of [IrCl 6 ] 2,3- with Br - trans/mer-isomers for n = 2,3,4 were formed. The stereoselectivi­ty of successive ligand exchange reactions is better for the Ir(III) than for the Ir(IV) system. The diamagnetic Ir(III) and the paramagnetic Ir(IV) complexes can be interconverted reversibly by redox reactions at low temperature. As shown by cyclic voltammetric measurements, the redox potentials within the series [IrCl n Br 6-n ] 2- 3- are linearly dependent on n. In aqueous solution the normal potentials are in the range of E o = 0.838 V ([IrBr 6 ] 2-,3- ) to E o = 0.908 V ([IrCl 6 ] 2-,3- ). The vibrational spectra of the mixed ligand complexes are assigned according to point groups D 4h , C 4v , C 3v and C 2v . They are similar for corresponding chloro-bromo-iridates, but distinguished by a shift of 10-25 cm -1 to higher wave numbers for most of the stretching vibrations going from Ir(III) to Ir(IV).

Opaque blue crystals of a new mixed valence cerium germanate have been prepared at elevated temperatures (1555 K) under careful thermoanalytical control. Single crystal structure analysis shows three different types of germanate anions [GeO 4 ] 4- , [Ge 2 O 7 ] 6- and [Ge 3 O 10 ] 8- , all ger­manium atoms being in tetrahedral coordination. Due to the larger number of oxygens per unit cell (Ce 2 Ge 2 O 7.2 ), with all the oxygens unambiguously located by X-ray single crystal structure analysis, this phase differs significantly from the corresponding cerium(III) germanate Ce 2 Ge 2 O 7 , which shows [GeO 4 ] 4- and [Ge 3 O 10 ] 8- , but no [Ge 2 O 7 ] 6- ditetrahedral groupings.

Polysulfides dissolved in non-aqueous solvents react under anaerobic conditions with nitric oxide to yield solutions of nitrosodisulfides. Through the action of NO upon (PNP) 2 S 12 1 [P = P(C 6 H 5 ) 3 ] in acetone a stable compound PNP · SSNO 2 could be obtained. 2 proved to be identical with a red PNP-salt which had been isolated as a product of the reaction of PNP·NO 2 with sulfur in acetone, hitherto taken for PNP · SSNO 2 . Clearly the product 3 of the action of triphenylphosphane upon 2 has to be regarded as PNP·SNO.

Phenyl substituted di-, tri- and tetraphosphines with the donor-functions in 1,2- or 1,3-position effectively replace Ph 3 P from Ph 3 P-P-PPh 3 + AlCl 4 − yielding cyclic five- and six-membered triphosphenium cations. In the 1:1-products of PhP(-CH 2 -CH 2 -PPh 2 ) 2 (4) and MeC(-CH 2 -PPh 2 ) 3 (2) the unused third phosphine function may interact as a nucleophile with the central phosphorus leading to a threefold T-shaped or pyramidal coordination thereof, respec­tively. From this attack, in the former case only, a rapid intramolecular exchange (ΔH ≠ = 9.6 kcal mol -1 ; ΔS ≠ = −9.9 cal mol -1 K -1 ) results, involving the two phosphine functions in the apical sites of the T-shaped transition geometry. This mechanism is suggested to describe the nucleophilic substitution at two-coordinate phosphorus in general. The cyclic triphosphenium cations can be protonated (and in part alkylated) to yield cyclic triphosphine-dionium cations.

The electrochemical behavior of thianthrenes 1-4, of selenanthrenes 5-8 (dibenzo-1,4-dichal- cogenins). of 2,2′-dithiobiphenyls 9 and 10 (dibenzo-1,2-dichalcogenins) as well as of the related compounds 11-13 were studied by cyclic voltammetry in acetonitrile. All dibenzodichalcogenins can be [oxidised in two one-electron-steps, the processes being totally reversible for 7, nearly reversible for 2 and 9, quasireversible for 1, 3, 4,10 and 13, and irreversible in all other cases. For 1- 4, 7, 9, 10 and 13 the diffusion coefficients of the electrochemically active species and the rate constants of the electron transfer are calculated from the potentials measured. Electrolysis of 9 in dichloromethane with tetrabutylammonium perchlorate as supporting elec­trolyte yields [dithiobiphenyl] + [C10 4 ] - (14), while oxidation by nitrosyl hexachloroantimonate gives [(dithiobiphenyl) 2 ] + [SbCl 6 ] - (15).

Nineteen values for 34 S-induced isotope shifts on the NMR frequency of directly bonded fluorine of fourteen S(II), S(IV), and S(VI) compounds are reported. The dependence of these 1 Δ 19 F( 34/32 S) values on the S-F bond length is demonstrated. Three reasons for this correlation are discussed. (1) A nonlinear dependence of nuclear shielding on bond distance. (2) Decreasing energy difference of two isotopomers with increasing bond distance. (3) Decreasing anharmonicity of the potential curve with increasing bond length. Some previously unknown S-F bond distances have been estimated by this correlation. The isotope shifts decrease with increasing temperature. This is attributed to vibrationally excited states in conjunction with a nonlinear dependence of nuclear shielding on bond distance. Furthermore, 34 S-induced isotope shifts on fluorine-19 over two bonds, 2 Δ 19 F( 34/32 S), have been observed for the first time, and the 33 S-induced isotope effect in SF 6 has been measured.

Bis(1-tert-butyl-2-methyl-η 5 -1,2-azaborolinyl)iron can be transformed into cationic (1-tert-butyl-2-methyl-η 5 -1,2-azaborolinyl)-η 6 -arene-iron sandwich complexes by the reaction with an excess of the arene (benzene (1), toluene (2), o-xylene (3), and mesitylene (4)), AlX 3 (X = Cl, Br) and aluminum at 80 °C with 60-70% yield. The sandwich cations are best isolated as PF 6 − salts. 1 H, 11 B, and 13 C N|MR data indicate η 5 coordinated 1,2-azaborolinyl ligands and η 6 bound arenes, in agreement with X-ray structure investigations on 1 and 2, using FeCl 4 2 and FeBr 4 2- anions because of the better crystal quality compared with the PF 6 − salts.

Carbonyl Olefin Complexes, Phosphite Substitution The four-step syntheses -starting with hexacarbonyltungsten -of symmetrically and asymmetrically substituted trans-bisphosphite-mer-tricarbonyltungsten complexes, (OC) 3 LL′(olefin)W, L = P(OMe) 3 , L′ = P(OMe) 3 or P(OEt) 3 , olefin = ethylene, methylmaleate, methylfumarate, methylacrylate (4a-4e), are reported.

The barriers of rotation of olefin ligands in (OC) 3 LL′W(olefin) complexes, L - P(OMe) 3 , L′ = P(OMe) 3 or P(OEt) 3 , olefin = ethylene, methylmaleate, methylfumarate, methylacrylate (1-4) have been determined from D-NMR measurements. The preferred olefin orientation has been deduced from an X-ray analysis of the tricarbonyl-triethylphosphite-trimethylphosphite-methyl-maleatetungsten compound 2. The influence of steric and electronic factors on the rotational process has been discussed by use of EHT-calculations.

Cathodically pretreated Raney-nickel-powder with a potential of -900 to -1000 mV (vs SCE) shows a positive potential shift of 200 to 300 mV in the presence of a hydrogen acceptor (coumarine or 1-ethinylcyclohexanol (1)). Pyridine and quinoline do not have any strong influence on the potential but retard the hydrogenation of coumarine. Acetylene derivatives as 1-ethinylcyclohexanol are hydrogenated in two steps applying a potential down to -1050 mV. At -1150 mV the selectivity is lost. With Raney-nickel-powder pre-treated with pyridine or hydrogensulfide the two-step selectivity of the hydrogenation of 1 is preserved applying also a potential of -1200 mV.

Ra-Ni with an artificial rest potential of -1000 mV (vs SCE) is shifted with different rates to more positive values after the addition of thioethers and carbon disulfide. Only with Na 2 S·9H 2 O a potential of -1100 mV (constant) is observed. Ra-Ni poisoned with sulfur is not reactivated neither cathodically nor anodically nor by the corrosive degradation at constant pH. Hydrogen structurally incorporated into the lattice of Ra-Ni (structural bonded hydrogen) is consumed by poisoning with thioethers and trivalent phosphorus compounds in a stoichiometric way. Ra-Ni-powder stepwise corrosively degradated up to 30% shows the same degree of desulfuri-zation as the original Ra-Ni. Desactivated Ra-Ni (loss of structural bonded hydrogen) is reacti-vated (56%) by cathodical treatment. In competing reactions the P-S, C-S, and C -P-bond in thiophosphinic esters, thioethers and trivalent P-compounds are hydrogenolyzed by Ra-Ni, the C-P-bond faster than the C-S-bond.

In contradiction to the experience the hydrodimer is formed as the main product in the electroreduction of coumarine using lithium compounds as a supporting electrolyt. It is assumed that the lithium ions are coordinated internally with the radicalanion A resp. B derived from coumarine. In this way the hydrodimerization is favoured. From 18 different compounds added as possible mediators to the catholyt only pyridine influences moderately the ratio: hydrodimerizationproduct/dihydroproduct.

To characterize nickel catalysts the capability for the hydrogenation and desulfurization under standard conditions is investigated. Depending on the conditions for the preparation the catalysts are subdivided in four classes: Raney-nickel-type, two types of nickel support catalysts and nickel-Al 2 O 3 -borides. Table I shows the rates of the hydrogenation of sodium cinnamate and the values for the desulfurization of diphenylsulfide, carbondisulfide and sodiumthiosulfate. The values for the specific surface, for the volume of the pores and for the adsorption energies are determined (Table II). ESCA-measurements give an orienting impression on the composition of the surface of some selected catalysts (Table III). Table IV contains some analytical values for the nickel-Al 2 O 3 -borides. The capability for the magnetizability of some catalysts before and after the desulfurization is registrated qualitatively.

5-Methylenecyclohexa-13-diene System, S, Excitation, Isomerizations 1,2,3,4,6-Pentamethyl-5-methylenecyclohexa-1,3-diene and 1,2,3,4,6,6-Hexamethyl-5-methy-lenecyclohexa-1,3-diene have been synthesized. The isomerizations following singlet excitation have been studied.

Quinolinetriones, Phosphonium Ylides, Wittig Reaction Quinolinetrione (1a) reacts with phosphonium ylides (2a-c) to yield the corresponding ethylenes (3a-c) together with triphenylphosphine oxide. Treatment of trione (lb) with ylides (2a-b) affords, on the other hand, the cyclobuta (c) quinoline derivatives (4a) and (4b), respectively. Structural assignments are based on analytical and spectroscopic evidence.

Dibromotrinitrosyltungsten, which dimerises via bromo bridges, is prepared by treating tungsten hexabromide with NO in CH 2 Br 2 suspension. It reacts with the Lewis bases acetonitrile, 1,2-dipyridyl, triphenylphosphane, and tetraphenylphosphonium bromide forming the octahedral complexes [WBr,(NO),(CH,CN),]. [WBr 2 (NO) 2 (dipy)], [ WBr 2 (NO) 2 (PPh 3 ) 2 ], [WBr 3 (NO) 2 ] 2 2⊖ , and [WBr 4 (NO) 2 ] 2⊖ , respectively. According to the IR spectra all dinitrosyl complexes possess cis-configuration of the nitrosyl groups.

Organoboration, Heterocycles, Multinuclear NMR 1,1-Organoboration of diethylamino-dimethyl-(1-propynyl)stannane (6), formed by an exchange reaction between the bis(propynyl)-(4) and bis-(diethylamino)dimethylstannane (5), with trimethyl-(2a) or triethylborane (2b) leads to highly reactive new heterocyclic compounds (7). Both, the coordinative N→B and the weak Sn-N bond are readily attacked by H-acidic compounds. Ammonia or primary amines are used as examples. Multinuclear NMR ( 1 H, 11 B, 13 C, 15 N, 119 Sn) data serve for the characterization.

Tetra-n-propyldibismutane reacts with equimolar amounts of di-p-tolylditelluride to yield p-tolyl-telluro-di-n-propylbismutane in high yield. This tellurobismutane is the first molecule with a Bi-Te bond. It has been characterised by elemental analysis and by NMR and mass spectra.

Spin trapping with N-t-butyl-α-phenyl nitrone (PBN) and 5,5-dimethyl-1-pyrroline-oxide (DMPO) has been utilized to identify the radicals in the gas phase of cigarette smoke. ESR spectra reveal predominantly alkoxy radicals which are continuously formed in smoke, but not directly in the flame.

The title substance has been isolated in a 0.0003% yield from wood of Salix caprea L. which, after felling, had been kept outdoors for one year. Its structure has been elucidated by spectroscopical and chemical methods.

Saraca asoca (Leguminosae), (―)-Epicatechin, Procyanidin (B2), 1 1′-Deoxyprocyanidin B The bark of Saraca asoca is used as a main ingredient in the preparation of Asoka Arishta, a drug indigenous to Sri Lanka. In this paper an investigation on some biologically active constituents of the bark is described. (―)-Epicatechin and procyanidin B2 were identified and a new compound, named 11′-deoxy-procyanidin B, was found. Its structure was elucidated by means of proton-NMR.

Dibenzo[b,g]heterocine-5,7-diones are synthesized by intramolecular ester condensations. Ring inversions of their distorted boat conformations occur with activation barriers of 10-15(42-62) kcal(kJ)/mole.