Group 13 organometallic chalcogen derivatives: their structures and behavior in solution

The syntheses, structures and equilibria which occur for 13–16 organometallic compounds are reviewed. The organoaluminum thiolates form dimers, trimers, and tetramers with central (AIS)₂, (AIS)₃, and (AIS)₄ rings in the solid state. The structures of the gallium and indium thiolates are dominated by dimers, but a tetramer has been observed for gallium and a trimer for indium. Only dimeric derivatives have been reported for the selenium and tellurium derivatives. In hydrocarbon solutions, the aluminiun thiolates establish equilibria between different aggregates and conformations with dimers and trimers most common. In the dimeric derivatives, [Me₂Al(μ-SME)]₂ and [Me₂Al(μ-SeMe)]₂, syn and anti conformations are observed in solution at low temperature by NMR spectroscopy. In the trimeric derivatives, the chair conformation is observed in the solid state. In solution, a chair to chair inversion occurs with the rate dependent on the substituents bound to the sulfur.     

Mesogenic behaviour in some pyrazole and isoxazole derivatives

Abstract

Several aromatic β-diketones with a different number of alkyloxy groups in the aromatic rings and their derived pyrazoles, isoxazoles and thallium (I) complexes have been synthesized. The potential mesomorphic properties of these compounds have been investigated by optical microscopy, DSC and X-ray diffraction. The pyrazoles and isoxazoles with one chain in each aromatic ring are mesogenic, showing smectic A and smectic C mesophases, whereas the pyrazoles and isoxazoles with two chains per ring and the β-diketones and thallium complexes are not. The mesogenic potentiality is shown to be related to the molecular linearity and to the number of alkyloxy groups. To the best of our knowledge, this is the first time liquid crystal properties have been described for pyrazole and isoxazole derivatives.     

Mesogenic behaviour in some pyrazole and isoxazole derivatives

Several aromatic β-diketones with a different number of alkyloxy groups in the aromatic rings and their derived pyrazoles, isoxazoles and thallium (I) complexes have been synthesized. The potential mesomorphic properties of these compounds have been investigated by optical microscopy, DSC and X-ray diffraction. The pyrazoles and isoxazoles with one chain in each aromatic ring are mesogenic, showing smectic A and smectic C mesophases, whereas the pyrazoles and isoxazoles with two chains per ring and the β-diketones and thallium complexes are not. The mesogenic potentiality is shown to be related to the molecular linearity and to the number of alkyloxy groups. To the best of our knowledge, this is the first time liquid crystal properties have been described for pyrazole and isoxazole derivatives.     

Thermal behaviour and adsorption properties of some benzothiazole derivatives

The thermal stability and the adsorption properties have been investigated for three benzothiazole compounds: 2-mercaptobenzothiazole (MBT), N-cyclohexyl-2-benzothiazole sulfenamide (NCBSA), and 2,2′-dibenzothiazole disulphide (BTD), reported in our early studies as corrosion inhibitors for carbon steel in different media. The electrochemical results were used to calculate the degree of surface coverage (θ). The adsorption mechanism of the three inhibitors was discussed according to the free energy of adsorption ( \( \Delta G_{{\text{ads}}}^{\circ } \) ) value obtained from Temkin adsorption isotherm, this being the best way to quantitatively express the adsorption process of their molecules on carbon steel surface. Thus, a mixed type mechanism involving the synergism between physisorption and chemisorption was proposed. The thermal analysis curves showed that, for the occurred events up to 470 °C, mass losses take place with endothermic effects followed by the total oxidation of the residue with an exothermic effect around 520 °C. Consequently, their effectiveness follows the order: BTD > NCBSA ≥ MBT, while the thermal stability ranges as follows: NCBSA < BTD ≤ MBT.     

Synthesis and structures of some di- and triferrocenylmethane derivatives

Some triferrocenylmethane derivatives were prepared by reaction of triferrocenylmethanol (5) with triphenylcarbenium tetrafluoroborate followed by a nucleophile. Crystal structure analyses of triferrocenylmethane (7) and of 1,1,1-triferrocenyl-2,2-dimethylpropane (11) show that the conformation adopted by the triferrocenylmethyl group differs significantly with the steric bulk of the substituent at the central carbon atom. Treatment of 1,1′-bis(tributylstannyl)ferrocene (13) with 1 equiv. of butyllithium followed by chloroethylformiate affords complexes with one (14), two (15) or three ferrocenyl units (16) depending on the amount of chloroethylformiate used. Compound 16 is the first triferrocenylmethane derivative with substituents at the opposite cyclopentadienyl ring. Threefold lithiation of this compound is shown to work using butyllithium followed by dimethylformamide.     

The crystal and molecular structures of some germatrane derivatives

The crystal and molecular structures of seven germatrane derivatives have been determined from three-dimensional X-ray data in order to investigate the main geometrical regularities of the germatrane molecules.     

Preparation and structures of some new 1H-pyrazole derivatives

Some new 3,5-diaryl-1H-pyrazoles were prepared from aryl methyl ketones via Claisen condensation with aromatic esters and followed by cyclization with hydrazine monohydrate. Their structures were confirmed by IR, ¹H NMR spectroscopy, mass spectrometry and elemental analysis. The X-ray structure for 3(5)-(4-tert-butylphenyl)-5(3)-(4-methoxyphenyl)-1H-pyrazole (2b) was presented. The results show that compound 2b exists as tautomers I and II, and its molecules are connected by the N–H···N intermolecular hydrogen bonds to form cyclic dimers consisting of the tautomers I and II.     

Molecular structures of some hydroxyazo compounds and their derivatives

The i.r. absorption spectra of 14 o-hydroxyazophenyl derivatives with increasing number of fused benzene rings of the aryl moiety are studied in solid state, in CCl₄ solution and in nujol mull. The i.r. spectral bands are assigned and indicate that these compounds exist in two tautomer forms. The OH group of the aryl moiety ortho to the azo group is responsible for the hydrazone structure. If solutions in CCl₄ are exposed to sunlight the strongly coloured compounds undergo a rapid bleaching, leading to a destruction of the azo group accompanied by an increase of hydrazone structures.     

Three-dimensional structures of some perhydro-1,4-thiazine derivatives

A number of perhydro-1,4-thiazine S-oxides and S,S-dioxides were synthesized. Their IR and PMR spectra were studied, and their dipole moments were determined. The latter were compared with the calculated values for the chair conformation with various orientations of the substituents. Conclusions were drawn regarding the configuration and conformation of the investigated compounds.The authors sincerely thank S. G. Vul'fson and I. I. Saidashev for their assistance in performing the research.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 410–415, March, 1972.     

Mass spectral behaviour of some m-dimethoxybenzene and sym-trimethoxybenzene sulphur derivatives

The mass spectra of fifteen m-dimethoxybenzene and sym-trimethoxybenzene sulphur derivatives (including thiols, sulphides, disulphides and trisulphides) have been investigated. Main fragmentation pathways have been proposed for each class of sulphur compound. Primary skeletal rearrangements of the molecular ions occurring in (poly)sulphur-bridged derivatives can provide a sensitive diagnostic tool both in structure elucidation and in the problem of locating methoxy substituents.     

Electrochemical behaviour of some neuroleptics: Haloperidol and its derivatives

The electrochemical characteristics of Haloperidol and related compounds, representative neuroleptics of the butyrophenone family, have been investigated as a function of pH and concentration by direct-current, alternating-current and differential-pulse polarography and cyclic voltammetry at a hanging mercury drop electrode. A single cathodic wave representing an irreversible two-electron reduction is obtained, and its half-wave potential differs from that characteristic of aromatic ketone reduction. Adsorption processes disturb the wave behaviour and an adsorption prewave is observed at high concentrations. Quantitative measurements were successful in the concentration range 1 x 10(-4)-1 x 10(-6)M (0.4 mg/l.), the lower concentration representing the detection limit by differential-pulse polarography.     

The behaviour of some ferrocene derivatives under electron impact

The behaviour of some mono- and di-substituted ferrocene compounds under electron impact has been investigated by means of low-resolution mass spectrometry. Some characteristic rearrangement processes have been observed and discussed.     

Thermal behaviour of some dibenzobicyclo[2.2.2]octane derivatives

A number of dibenzobicyclo[2.2.2]octane derivatives have been studied due to the interest of such compounds as ligands for coordination compounds with potential biological activity. Their thermal behaviour has been analyzed in order to find out more information about their fragmentation. A connection between the bridge substituents and the fragmentation process has been observed.     

On the electronic and molecular structures of some fluoro-substituted cyclopropane derivatives

Ab initio calculations of double zeta quality have been carried out on cyclopropyl fluoride and 1,1-difluorocyclopropane. A partial geometry optimization has been carried out, and results have been compared to cyclopropane. An attempt is made to explain the differences in structure between cyclopropane and the fluorine derivatives.     

Thermal behaviour of some derivatives of malic acid with calcium and strontium

Results are presented on the thermal behaviour of two derivatives of malic acid. The decomposition intermediates obtained at about 400?C were identified as derivatives of malonic acid. For some individual thermal decomposition steps, the values of the non-isothermal kinetic parameters were determined.     

Electronic structures of some of C84 fullerene isomers and the structures of their perfluoroalkyl derivatives

The electronic structures of the pristine fullerene molecules have been shown for the first time to be is the most important factor affecting the distribution of addends in the addition reactions of perfluoroalkyl radicals R^F to C₈₄ fullerene, and most likely positions of addends on the fullerene core are hexagons with delocalized π-bonds.