Band 31, Heft 7

The crystal structures of the title compounds were determined. Both compounds are isostructural and do not exist as dimers as previously assumed but as trimers in the form of six-membered rings in the chair conformation. Mean values of the bond distances are B-Cl 1.80 A, B-Br 1.96 A, B-S 1.95 A, S-C 1.84 A.

N-Diorgano-N′-bis(trimethylsilyl)sulfamide (1 a, b) and Ν,Ν,N′,N′-tetrakis (trimethylsilyl)sulfamide (4) react with trithiadiazyl dichloride (2) to give the trithiazolidenes (3 a, b) and (5).

Silicon(IV) formate has been prepared by the reaction of silicon(IV) chloride and anhydrous formic acid. The compound has been characterized by elemental analyses, thermogravimetry and infrared spectral data.

Cathodic reduction of MoS 2 in DMSO electrolytes containing alkali cations A + results in the formation of defined ternary phases A+ 0.125 (DMSO) y [MoS 2 ] 0.125 - with highly mobile solvated interlayer cations. Reduction of MoS 2 in DME electrolytes yields similar products. Basal spacings are dependant on solvent type and on ionic radius of A + . Further reduction of these compounds is associated with irreversible processes.

Investigations on several tetrakis(arylisonitrile)-metal complexes of general stoichiometry M(CNR) 4 n+ X n - with M = Rh(I), Rh(III), [n =1], [n = 3] or Co(II), [n = 2], R = p-tolyl, p-N,N-dimethylaminophenyl, p-nitrophenyl, e. g. and X - = iodide, ClO 4 - , [B(C 6 H 5 ) 4 ] - e. g. are described. The paramagnetic complexes of stoichiometry Co(CNR) 4 I 2 dimerize in organic solvents to yield dinuclear diamagnetic cations with linear iodide bridges. The amount of association depends on the iodide content and on experimental parameters like temperature and/or concentration and can be followed by IR, ESR and/or NMR techniques. Treating of these compounds with ions X - = ClO 4 - or [B(C 6 H 5 ) 4 ]- gives the dinuclear and diamagnetic complexes of stoichiometry [I-Co(CNR) 4 -I-Co(CNR) 4 I]X. The corresponding isonitrile compounds of rhodium(I) associate in solution to yield linear stacks in the crystals. The solid state properties depend strongly on the type of ligand and the counter anion and vary considerably with the conditions of crystallization. The rhodium(I) species are able to react with the corresponding tetrakis(arylisonitrile)-rhodium(III) complexes to mixed valence solids.

The adsorption of acetone on MgO was studied by IR spectroscopy, the desorption products were analyzed with a mass spectrometer. Furthermore, the heat of adsorption and the coverage of the surface were calculated from adsorption isothermes measured at various temperatures. Acetone is adsorbed over (weak) hydrogen bonds to surface hydroxyl groups as well as coordinatively bound to the cation Mg 2+ . This bonding to the cations causes strong shifts of the carbonyl band (up to 100 cm -1 ) and the CH 3 bands (Δν≈55 cm -1 ) to lower wavenumbers. At 120°C, desorption of acetone, and at 320°C and 400°C of methane is detected. Using d 6 -acetone or D 2 O, the methane observed can be shown to be formed from hydrogen of acetone rather than with participation of hydrogen of surface hydroxyl groups.

The kinetic model for the hydroformylation process as given in a previous paper (SEELIG 1 ) is extended in as far as the concentrations of all three substrates (olefin, H 2 , CO) are allowed to move freely, whilst in the first investigation this was the case only for CO, the concentrations of olefin and H 2 being kept constant. So the derived hysteresis loop of [CO] va influx of CO is shifted back and forth by the varying [olefin] and [H 2 ], causing oscillations for particular combinations of the parameters. These oscillations are due to the substrate inhibition by CO and are not the result of instabilities of some external control circuit; so they would occur even in a perfectly isothermal open system.

The molecular ions of ten monoterpenes show no or only minor isomerisation to a common intermediate or an equal mixture of structures prior to or during collisional activation. The C 7 H 9 +ions, however, from these monoterpenes and some other precursors exhibit the same abundance ratios for their collision induced decompositions. From the characteristic release of kinetic energy possible structures of the decomposing gaseous C 7 H 9 + ions can be elucidated. It is shown that the ions eliminating H 2 resp. CH 4 possess a different structure in the transition state.

Catalytical hydrogenation of unsaturated compounds in acetic acid with the homogeneous catalyst prepared from H 2 PtCl 6 + SnCl 2 • 2 H 2 O and the heterogeneous catalyst, prepared from H 2 PtCl 6 and H 2 , were carried out. A comparison of the results reveals two types of substrates, some are readily hydrogenated by the homogeneous the other ones by the heterogeneous system. Turnover numbers up to 1500 were observed. With the heterogeneous catalyst ethylbenzene is hydrogenated to ethylcyclohexane under mild conditions.

With heterogenized RhCI(PPh 3 ) 3 fixed on glass wall of the reaction vessel mesityloxide, acrylicacidethylester and cyclohexene are hydrogenated without solvent at 50°C with high reaction rates and high turnover numbers. The catalyst, once prepared can be used for oxidation of substrates with molecular oxygen as well. Characteristic data to describe the activity of catalysts are suggested.

The title compound crystallises in the monoclinic space group, Cc, Z = 4, with a = 12.370(1), b = 19.447(1), c = 7.786(1) Å, β = 90.82(1)°. The structure was solved by direct methods and refined to R = 0.070 for 2163 independent reflections. Trigonal-bipyramidal geometry is observed at phosphorus with the ring oxygens occupying the axial sites. The plane of the phenyl substituent makes a dihedral angle of 20.2° with the equatorial plane. The molecules are linked into infinite chains in the [010] plane through (CH 2 )O ••• H—O(CH 2 ) hydrogen bonds of length 2.77 A.

Thermal cis →-trans isomerization of eight N-benzylideneanilines with donor and/or acceptor substituents in the para, para'-positions was studied in different solvents by observing the rapid relaxation to the thermodynamic stable trans isomer following flash photolysis. With the push-pull effect of the substituents in the direction of the N-aryl group the rate constant at 25°C is by three powers of 10 faster compared to the N–benzylideneaniline with opposite arrangement of substituents. The rate constants are independent of the nature of the substituents in the para-position of the benzylidene group. The rate constants of N-(4-nitrobenzylidene)-p-anisidine are linear functions of the solvent polarity scale based on solvatochromic shifts (Kosowers Z-value or Dimroths E T -value). With increasing push-pull effect of the substituents in the direction of the N-aryl group the rate constants do no longer depend on the polarity of the solvent. The observed solvent effects on the rates and the activation energies for thermal cis→ trans isomerization suggest that the transition state of the reaction is less polar than the ground state of the sterically hindered cis-N-benzylideneaniline, thus favouring an inversion mechanism to become operative with respect to the N-benzylideneanilines.

From conductivity changes following a 1 µs electron pulse applied to Ν 2 Ο saturated H 2 O or D 2 Ο solutions of acetic acid 2-hydroxyethyl esterthe rate constants of the monomolecular decay of the radical HO-ĊH-CH 2 -OCOCH 3 (1) in H 2 O and of DO-ĊH-CH 2 -OCOCH 3 in D 2 O were derived, reaction (1). A value of k 1 of 5.5 · 10 5 s -1 ± 25%, at 22 to 24°C, independent of the above solvents and of pH (or pD) was obtained. It is concluded that the rate determining step of reaction (1) is the heterolytic fragmentation of the carbon acetate bond in 1 followed by formation of H + .

The synthesis of several so far unknown mono- and oligo-galvinols and galvinoxyls is described. The ESR hyperfine splitting measurements in liquid solution indicate that the spin exchange frequency is greater than the hyperfine splitting in the galvinoxyl biradicals (J≫a). The electronic absorption spectra of the galvinols and galvinoxyls are discussed taking into account the different prototropic and redox equilibria, respectively. Using magnetic susceptibility measurements the singlet-triplet and doublet-quartet splitting is studied.

ESR powder spectra of several differently bridged bis-galvinoxyl biradicals have been recorded. The spectra can be interpreted in terms of a weak electron-electron dipolar coupling between the unpaired spins of randomly oriented triplet molecules. Using MO-theory and a point charge model for atomic orbitals a detailed structural analysis is performed on the basis of quantum mechanical calculations. Taking into account the twist angles between the various aryl rings the experimental data can be explained satisfactorily.

After diazotation 2-amino-3-hydroxythiazolium chlorides react with activated aromatic compounds to build azo dyes. In absence of coupling components 2-amino-3-hydroxy-4-methylthiazolium chloride gives a colour reaction with nitrite ions, which is suitable for photometric detection of nitrite in aqueous solution.

With 98% formic acid 1,5-cyclo-10α-cholestan-2-on (5) is isomerized to yield 19-nor-5α- methyl-Δ 1.(10) -cholesten-2-on (6). Reaction of 5 with BF 3 in benzene yielded mainly 6; as by-product des-A,B-nor-10-3'(2'-cyclopentane-1'-on)-cholestane (8) was obtained. On reaction of 5 with FeCl 3 • 6 H 2 O in absolute methanol or ethanol 5 α-methoxy-, or 5 α- ethoxy-10 a-cholestan-2-one (18, resp. 14) was formed.

Diethyl phenylthiocarbamoylmalonate (2) reacts with β-cyanoethylhydrazin (1) to yield ethyl 3-anilino-2-pyrazolin-5-one (3) via decyanoethylation of the reaction intermediates. Whereas 2 reacts with hydrazine hydrate in refluxing ethanol to yield a mixture of 3-anilino-2-pyrazolin-5-one (4) and the hydrazide (5), the diethyl ester (6) is formed on treatment of 2 with the same reagent in a cooled ethanolic solution. On the other hand, 2 reacts with hydrazine hydrate in the absence of a solvent to yield the carboxylic acid (7). Benzoylacetonitrile reacts with phenylisothiocyanate to yield the thioanilide (8). The latter compound neither reacts with hydrazine hydrate not β-cyanoethylhydrazine.

Diorganyldichlorosilanes (2 a, b) react with the disilylated sulfamides (1 a, b) to give the cyclodisilazanes (3a-c), however with the monosilylated sulfamide (4) the silazanes of type 5 are formed. Reaction of 1 a with bis-(dimethylchlorosilyl) sulfurdiimide (6) affords the cyclic compound (7).

The formation, 1 H NMR spectroscopic and X-ray crystallographic investigations of a double hydrogen-bridged tricyclic system of a cyclotriphosphazadiene derivative, [N 3 HP 3 (O)Cl 2 (NEt 2 ) 3 ] 2 are described and discussed. This is the first neutral molecule having both cyclophosphazene and cyclophosphazane character to be structurally investigated.

The synthesis of trimethylphosphazenyland triphenylphosphazenyl-fluorocyclotri-phosphazatrienes, N 3 P 3 F 6-n (NPR 3 )n, by a silylation method using Me 3 SiNPR 3 (R = Me or Ph) is reported. More phosphazenyl groups can be introduced if R = Me than if R = Ph. Isomers have been isolated, as have been mixed phosphazenyl derivatives, N 3 P 3 Fe 6-n-m (NPR 3 ) n (NPR 3′ ) m (R = Ph, R′ = Me). Substituted fluorophosphazenes, N 3 P 3 F 6-n X n (X = Ph, NMe 2 , or OPh) also undergo similar reactions.

An X-ray crystallographic structure investigation of pentachloro(triphenylphosphazenyl)cyclotriphosphazatriene, N 3 P 3 C 15 (NPPh 3 ), reveals a novel conformation (type I) of the triphenylphosphazenyl group with respect to the adjacent ring segment. This is contrasted with the structure of gem. –N 3 P 3 CI 4 Ph(NPPh 3 ), where a type II conformation is observed.

Four-bond phosphorus-phosphorus coupling constants have been measured from the 31 P NMR spectra of phosphazenylcyclophosphazenes. Their magnitude appears to be related to the conformation adopted by the phosphazenyl-group relative to the phosphazene ring.

The electrochemical (catalytical) oxidation of tent-butylisocyanide yields the dimer, trimer and higher oligomers.

The melting curve of NaClO 3 was determined to 42 kbar. The equation t m (°C) = 270 + 15.09 (P-0,85) — 0.4044 (P-0.85) 2 + 0.004555 (P-0.85) 3 fits the data with a standard deviation of 5°C.

The reaction of C(NMe 2 )4 with CO 2 , COS and CS 2 yields hexamethylguanidiniumsalts by transfer of a dimethylaminogroup to the carbonic acid derivate. 1 H, 13 C and IR spectra of the salts are discussed.

Direct and sensitized photolysis of 2-(a- diazo-benzyl)-pyridine-1-oxide (2) as well as its thermolysis in deoxygenated solvents resulted 2-benzoylpyridine (3) in nearly quantitative yield. As a geometrical consequence of the intramolecular abstraction of oxygen from the N→O group by the triplet carbene (1) the formation of an oxazetine intermediate (4) is discussed.

Retention of configuration at phosphorus is found in the LiAlH 4 -induced fission of the allyl group from chiral phosphonium salts.

On the contrary to the photochemical behavior the title compounds do not isomerise to a common intermediate prior to or during electron impact induced fragmentation. The unusual methyl elimination from the trans(2)-butenoic acid methyl ester probably is accompanied by a concerted [1.3] methoxy rearrangement from the ester function on to the β carbon atom.

A new improved synthesis of methionineenkephalin is described. For methionineenkephalin the structure L-Tyr-Gly-Gly-L-Phe-L-Met-OH has been suggested most recently. The peptide is synthesized from Boc-Gly-Gly-OH, H-L-Phe-OMe, Boc-L-Tyr(Bzl)-OH and H-L-Met-OMe by means of “classical” methods.