Volume 29, Issue 11-12

The relative stability of the siliconbromidechlorides is discussed on the timedependence of the dismutation reaction of SiCl 3 Br, on the measured appearence potentials of SiCl 3 , from SiCl 3 Br and SiCl 4 respectively and on the enthalpies of the hydrolysis reactions. The relative strengths of the Si-Br-bonds of the different compounds were estimated, using SiCl 4 as a standard.

The 13 C PFT NMR and 1 H CW NMR spectrum of bis(h 5 -t-butylcyclopentadienyl)vanadium were recorded, and the signals assigned. A distinct superiority of the 13 C spectroscopy is shown. As the observability of these signals depends on the line width the influence of the electron-spin relaxation time τ e on dipolar and contact broadening is analysed. It is found that both broadenings should be of similar size. Except for the ring carbon atoms of nickelocenes the 13 C signals of paramagnetic metallocenes should be easy to observe. Using the 13 C results dipolar as well as contact contribution to the experimentally found line width are separated, and τ e is determined. From T e it is concluded that zero-field splitting does not essentially affect the electron-spin relaxation.

Single crystals of Cu 0.64 V 2 O 5 were prepared by hydrothermal synthesis. The X-ray investigation shows an orthorhombic unit cell: α = 11.313, b = 4.804 and c = 3.613 Å, space group D 2h 13 -Pmnm. Cu 0.64 V 2 O 5 has a network equal to that of V 2 O 5 . Copper is inserted between the layers with an extraordinary coordination and remarkable long Cu–O distances.

HNSOF 2 reacts with metal carbonates to form the salts Li + NSOF 2 - , Cs + NSOF 2 - and Ag + NSOF 2 . The reaction of Ag + NSOF 2 - with halides yields the new dimethyltin compounds (CH 3 ) 2 SnClNSOF 2 , (CH 3 ) 2 SnBrNSOF 2 and (CH 3 ) 2 Sn(NSOF 2 ) 2 . The IR spectra of the sulfuroxidedifluorideimide salts are compared with the isoelectronic SO 2 F 2 . All compounds are characterized by analysis, IR, NMR and mass spectra.

Dimethyltinselenid reacts with diorganyliodoboranes to give R 2 B—Se—BR 2 . The compounds with R = C 6 H 11 and C 6 H 5 are stable, whereas with R = CH 3 and C 4 H 9 decomposition to polymeric (RBSe) n was observed. Diboryldiselenanes have been obtained from (C 5 H 5 ) 2 TiSe 5 and R 2 B—I as well as from borolane and elemental selenium. At higher temperature these diboryldiselenanes decompose to form triselenadiborolanes and trialkylboranes.

The assignment of the H 2 O libratory vibrations in crystal hydrates to the rocking or wagging vibration alternatively using the isotope shift of the HDO librations is discussed. IR spectroscopic data on BaCl 2 · 2 H 2 O, BaBr 2 · 2 H 2 O, SrCl 2 · 2 H 2 O, BaCl 2 · H 2 O, BaBr 2 · H 2 O, SrCl 2 · H 2 O, SrBr 2 · H 2 O and on the deuterated compounds of these hydrates are included.

The preparation of Na[Co(SO 3 ) 2 (NH 3 ) 2 ] · 2 H 2 O, Na[Co(SO 3 ) 2 en] · 2 H 2 O and [Co(NO 2 )-(SO 3 )en 2 ] is described. Infrared and visible absorption spectra of the complexes have been measured.

The 19 F NMR spectra of some PF 5 -base complexes (base = trimethylamine, 3-methylpyridine, 3,5-dimethylpyridine) were studied. It is concluded that the spectra cannot be interpretated on a first order basis, and have to be rationalized in terms of an AB 4 X spin system; this was confirmed by computer simulation of theoretical spectra and their comparison with experimental spectra.

A method to analyze spectrophotometric titrations of one-step dissociation-equilibria is applied to titrations of polyelectrolytes with small pK-differences. As criteria for the spectrophotometric uniformity, absorbance and absorbance-difference-quotient diagrams are referred to. By means of these methods otherwise not determinable absorbance coefficients and pK-values of the uniform parts of the titration can be determined. The methods are demonstrated using the titration of o-phthalic acid and (1,2,4)-benzenetricarboxylic acid.

The addition of molecular iodine to solutions of tertiary aliphatic amines in liquid sulphur dioxide is found to result in the formation of stable free radical oxidation intermediates. In triethylamine solutions, oxidised under these conditions, aromatisation appears to take place to produce a pyridinyl radical. Radicals formed from N-ethyldimethylamine, Ν,Ν-diethylmethylamine and tri-n-propylamine on the other hand appear to be essentially aliphatic in character, with two of the N-alkyl groups intact. The magnitude of the measured coupling constants however, implies some delocalisation in the “damaged” alkyl group, possibly via a tautomeric mechanism. A number of mechanistic possibilities are explored to account for the roles played by iodine and sulphur dioxide in these reactions.

The steady state photolysis of 5-bromouracil (BU) in aqueous solution has been studied as a function of wavelength, pH, temperature, and hydrogen-donor concentration. Under all conditions studied, the primary reaction is shown to be C-Br bond cleavage followed by abstraction from the hydrogen-donor to give uracil and HBr. At pH > 12 further products are formed. In deoxygenated aqueous solution at pH 6, 20°C, and 254 nm, the quantum yield of BU consumption, Φ (-BU), is 1.8 × 10 -3 independent of hydrogen-donor type or concentration (e.g. 3 × 10 -2 to 2 M MeOH). With increasing pH, Φ (-BU) increases stepwise to 0.012 at pH 10 and to 0.28 at pH 14. pK-values calculated from these data are the same as ground state pK values. Φ (-BU) increases with temperature with an activation energy of approx. 3.4 kcal/mol. Φ (-BU) increases with photon energy. Above 2 M MeOH Φ (-BU) increases reaching Φ (-BU) = 0.025 in neat MeOH. Similar high, solvent dependent, values are obtained for other hydrogen-donor solvents. In neat organic solvents an additional reaction with BU induced by solvent radicals was observed. These results have been explained in terms of a homolytic dissociation of the C-Br bond of the excited BU followed by recombination or H atom abstraction by the radicals. At high hydrogen-donor concentration H atom abstraction can compete with cage recombination. A comparison has been made between BU photolysis in organic, hydrogendonor solvents and BU photolysis within the DNA of bacteria or phages. It has been concluded that the much higher quantum yields observed for chain breaks in the photolysis of DNA containing BU compared to photolysis of BU in aqueous solution is due to the high local concentration of hydrogen-donors (sugar molecules) within the DNA molecule, even in dilute aqueous solution.

Polybrominated HBr-donors were irradiated with UV light of the wavelength λ = 257 nm and 290 nm in methanolic solution and methanolic spiropyran solution. The quantum efficiency of the generation of HBr has been determined and discussed. With spiropyran present in the irradiated solutions the results can be explained only by the assumption of an energy transfer process between spiropyran and HBr-donors.

Dimethylsulfoniumphenacylbromide reacts with arylisocyanates in the presence of N-ethyldiisopropylamine to stable dioxo-S-ylides (1-5). Compounds 6-16 are obtained by variation of the starting sulfonium salts and isocyanates. Tolyl-2,4-diisoyanate yields with dimethylsulfoniumphenacylbromide the 1:2 adduct 17, while with the corresponding triphenylphosphoniumbromide the 1:1 adduct 18, with a free isocyanate group, is obtained.

Crystalline N-(para-chlorophenyl) phthalanilic acid undergoes a topochemical cyclization reaction with the elimination of water yielding crystalline N-(para-chlorophenyl) phthalimide. The crystal structure of the imide product has been determined and compared to the previously determined structure of the reactant. The reaction from this particular crystalline phase of N-(para-chlorophenyl) phthalanilic acid is enhanced by the presence of a high energy molecular conformer of the acid, little molecular motion necessary for reaction, and only a minor rearrangement required to pack into the imide structure after the reaction. A detailed molecular mechanism for this reaction is proposed involving some bond rotation, but little movement of the molecule as a whole.

Reaction of 2-acetoxy-cyclohexa-3,5-dienones (“quinol acetates”) with BF 3 or (CH 3 CO) 2 O/BF 3 in the presence of benzene derivatives (mesitylene, mesitol, 1,3-dimethoxy benzene, 1,3,5-trimethoxy benzene) yields biphenyl and diphenyl methane derivatives whose structure has been elucidated mainly from their spectroscopic data.

Treatment each of 3-mercapto-1,2,4-triazine derivatives (1 a) and (2b) with alkyl (or aryl) halides afforded the corresponding 3-alkyl (or aryl)mercapto-1,2,4-triazine derivatives (lb-e) and (2b-e) respectively. Treatment each of compounds (lb-e) and (2b-e) with different amines effected the formation of the corresponding 3-substituted-amino-1,2,4-triazine derivatives (lg-k) and (2g-k). The 4,5-dihydro-derivatives (3 a, c, d) were obtained by reduction of the corresponding triazines (la, f, g) with different reducing agents. The structure of compound 3 d was confirmed via synthesis through another route. The triazine (1f) reacted with Grignard reagents to give the corresponding 5-alkyl(benzyl)-4,5-dihydro-1,2,4-triazine derivatives (4a-c). The antagonistic properties of the triazines (1 a-k) and (2 a-k) were tested against some Gram positive and Gram negative bacteria as well as the fungus Candida albicans.

Novel organosilicon peroxides, their preparation, properties, and 1 H—NMR spectra are discussed.

N,N′ -Bis(trimethylsilyl)-sulfur(IV)diimide and Bis(trimethylsylilimido)-sulphoxide react with chlorsulphonicisocyanate to give the sixmembered heterocycles 3 and 5.

Arylazo complexes of the type CpCr(CO) 2 -(N = N-C 6 H 4 -X(p)) (X = H, OCH 3 , CH 3 , F, NO 2 ) have been obtained by the reaction of CpCr(CO) 3 Na with p-substituted aryldiazonium tetrafluoroborates in glacial acetic acid.

The structure of [(CH 3 ) 2 Si] 2 S 2 N 4 has been determined from threedimensional diffractometer data and refined by least squares methods to R = 0.07. The unit cell is orthorhombic with four molecules per unit cell and a = 599,5 pm, b = 2300.9 pm, c = 841.9 pm. Wie von ROESKY und WIEZER 1 gezeigt werden konnte, lassen sich im achtgliedrigen Ringsystem des S 4 N 4 2 Schwefelatome durch Si(CH 3 ) 2 -Gruppen ersetzen. Die Struktur dieser Verbindung haben wir röntgenographisch bestimmt.

Ternary solvated layer chalcogenides (A x ) x+ (Solv) y [MX 2 ] x- (1) may be oxidized to the binary compounds MX 2 . The reaction is reversible layered chalcogenides MX 2 can be reduced by chemical or electrochemical means to solvated polyelectrolyte compounds 1.

Chain structure, Force constants From vibrational spectra chain structures are predicted for AuCl and AuBr; bond angles, bond lengths and force constants have been estimated for these aurous halides.

CuAlS 2 and CuAlSe 2 decompose at high pressures and temperatures according to 5 CuAlX 2 → 2 Cu 2 X + CuAl 5 X 8 .

A mixed trinuclear Co(III), Rh(III)-ammine complex containing oxalate as a tridentate bridging ligand has been prepared by reacting [Rh(NH 3 ) 5 C 2 O 4 H](ClO 4 ) 2 with tri-µ-hydroxo-bis[triamminecobalt(III)]perchlorate in acidic aqueous solution.

The first superconducting polyelectrolytes are reported. The compounds are hydrated ternary layer chalcogenides (A x ) x+ (H 2 O) y- [TaS 2 ] x- ; for A + = alkali metal ion the transition temperatures Tc range from 2,80°K to 5,45°K with T c being dependent on the cation radius.

The rate of the photoinitiated autoxidation of sulfite is considerably influenced by ferric ions in trace concentrations.

Imidosulfenylhalides (CF 3 ),C=N–SX (X= Cl, F) are prepared from (CF 3 ) 2 CN 2 , and (NSCl) 3 and Hg(NSF 2 )2, respectively.

The possible occurrence of non classical conjugation involving sulphur in aryl benzyl sulphides has been investigated. From the charge transfer spectra and the stability constants of the complexes formed between iodine and aryl benzyl sulphides, and from the UV spectral behaviour of the ArI–S–CH 2 –Ar, system, it may be concluded that through space conjugation in aryl benzyl sulphides is not important.

The chlorine exchange between hexachloropropene and SbCl 3 -( 36 Cl) is retarded by electron donors. The activity of hexachloropropene-( 36 Cl) is a value for the donor.

A new synthesis for the tripeptide Pyr-Ser-Gly-NH,, with mutual GH-RH activity is described. Z-L-Pyr-OH is reacted with HO-NSu to the protected amino acid derivative Z-L-Pyr-ONSu. Further intermediates in the synthesis are Z-L-Pyr-L-Ser(Bzl)-OH and Z-L-Pyr-L-Ser(Bzl)-Gly-NH,.