Matthias W. Haenel

Recent progress in coal structure research

Abstract Coal is physically and chemically a heterogeneous rock which mainly consists of organic material. It is generally agreed that the organic coal material has been formed from plant debris. In a first, mainly biochemical stage, peat was laid down which in a later geochemical stage underwent coalification over a period of up to several hundred million years under the influence of pressure and temperature caused by overlying sediments. The organic sedimentary rock thus formed is composed of fossilized plant remains called macerals, and mineralized inclusions. The macerals are microscopically distinct areas which are differentiated into three major classes: vitrinite, exinite (or liptinite) and inertinite. Vitrinite occurs most frequently and is believed to be derived from woody plant material (mainly lignin), and the exinite from lipids and waxy plant substances. The origin of inertinite is possibly charcoal formed by prehistoric pyrolysis processes. As the result of its origin, coal is an almost non-volatile, insoluble, non-crystalline, extremely complex mixture of organic molecules varying considerably in size and structure. Detailed structural characterization has been found to be extremely difficult, so that coal structure research is still a challenging task and continues to be pursued intensively. In principle, two approaches can be used for determining the chemical structure. One attempts to degrade the coal macromolecules into representative fragments and to derive the original structure from the structures of such fragments. The alternative approach attempts to characterize coal directly by techniques which allow the non-destructive investigation of solid materials. Such techniques are, for instance i.r. and solid-state n.m.r. spectroscopy, X-ray diffraction and small angle scattering, electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS, XANES, EXAFS), or Mossbauer spectroscopy. While for some of these techniques the application to coal is severely hindered owing to the lack of necessary transmittance or crystallinity, others have been developed recently in material science as important tools for the investigation of solids. In recent years further important insights into structural features of different coal varieties have been gained using new physical and chemical methods and known techniques that have been further developed. Some of these methods are reviewed and the results obtained from application to coals are discussed in the context of coal structure.

BIDENTATE PHOSPHINES OF HETEROARENES : 9,9-DIMETHYL-4,5-BIS(DIPHENYLPHOSPHINO)XANTHENE

Twofold lithiation of 9,9-dimethylxanthene with n-butyllithium and N,N,N′,N′-tetrametylethylenediamine (TMEDA) in boiling n-heptane followed by reaction with chlorodiphenylphosphine (Ph2PCl) yielded the title compound 4. The phosphine ligand was characterised by 1H NMR, 13C NMR, 31P NMR spectroscopy and single crystal X-ray structure analysis. The folded and deformed xanthene unit causes a remarkably short P…P distance of 4.1 A which in turn results in a large coupling 6JPP′ = 27.3 Hz.

Structural features and mesophase formation of coal-tar pitch fractions obtained by preparative size exclusion chromatography

Abstract High-temperature coal-tar pitch was fractionated by preparative size exclusion chromatography on Sephadex LH-20 in pyridine at 60 °C. The fractions obtained were characterized by elemental analysis, molecular weight determination (vapour pressure osmometry), i.r. spectroscopy, and TGA. The linear correlation observed between log molecular weight (range 200–2500 Dalton) and elution volume shows that fractionation of the pitch was mainly due to size exclusion and that interfering polar adsorption on the gel was essentially avoided. This is supported by the similarity between the i.r. spectra and elemental analyses of the fractions, respectively. The molecular weight distribution of the nitrogen-containing pitch constituents is also discussed. Selected samples were heat-treated using hot-stage microscopy. The reactivity of the fractions towards polymerization is lower than that of the unfractionated pyridine-soluble portion of pitch. This leads to a slower increase in viscosity of the fractions, thus allowing the formation of larger mesophase spheres. Addition of a small amount of a low molecular weight fraction to a high molecular weight fraction enhanced polymerization.

Polymorphic Enzymes, Urinary Bladder Cancer Risk, and Structural Change in the Local Industry

In the 1990s, an uncommonly high percentage of glutathione S-transferase M1 (GSTM1) negative bladder cancer cases (70%) was reported in the greater Dortmund area. The question arose as to whether this uncommonly high percentage of GSTM1 negative bladder cancer cases was due to environmental and/or occupational exposure decades ago. Thus, 15 years later, another study on bladder cancer was performed in the same area after the coal, iron, and steel industries had finally closed in the 1990s. In total 196 bladder cancer patients from the St.-Josefs-Hospital Dortmund-Hörde and 235 controls with benign urological diseases were assessed by questionnaire and genotyped for GSTM1, glutathione S-transferase T1 (GSTT1), and the N-acetyltransferase 2 (NAT2) tag SNP rs1495741. The frequency of the GSTM1 negative genotype was 52% in bladder cancer cases and thus lower compared to a previous study performed from 1992 to 1995 in the same area (70%). NAT2 genotypes were distributed equally among cases and controls (63% slow acetylators). Fewer GSTT1 negative genotypes were present in cases (17%) than in controls (20%).

Hydrogenation of CO2 to Formic Acid with a Highly Active Ruthenium Acriphos Complex in DMSO and DMSO/Water

Abstract The novel [Ru(Acriphos)(PPh3)(Cl)(PhCO2)] [1; Acriphos=4,5‐bis(diphenylphosphino)acridine] is an excellent precatalyst for the hydrogenation of CO2 to give formic acid in dimethyl sulfoxide (DMSO) and DMSO/H2O without the need for amine bases as co‐reagents. Turnover numbers (TONs) of up to 4200 and turnover frequencies (TOFs) of up to 260 h−1 were achieved, thus rendering 1 one of the most active catalysts for CO2 hydrogenations under additive‐free conditions reported to date. The thermodynamic stabilization of the reaction product by the reaction medium, through hydrogen bonds between formic acid and clusters of solvent or water, were rationalized by DFT calculations. The relatively low final concentration of formic acid obtained experimentally under catalytic conditions (0.33 mol L−1) was shown to be limited by product‐dependent catalyst inhibition rather than thermodynamic limits, and could be overcome by addition of small amounts of acetate buffer, thus leading to a maximum concentration of free formic acid of 1.27 mol L−1, which corresponds to optimized values of TON=16×103 and TOFavg≈103 h−1.

4,5-bis(diphenylphosphino)acridine: A new type of tridentate phosphorus-nitrogen-phosphorus ligands

Abstract Reaction of 4,5-difluoroacridine (8) with two equivalents of potassium diphenylphosphide (Ph2PK) yielded the title compound 3. Contrarily, diphenylphosphine (Ph2PH) reacted with 8 under addition, and 4,5-difluoro-9-diphenyl-9,10-dihydroacridine (12) was obtained. Compound 8 was prepared from 2-amino-3-fluorobenzoic acid (13) in a four step synthesis. As it is shown by the preparation of the metal complexes 4,5-bis(diphenylphosphino)-acridine-palladium dichloride (16) and 4,5-bis(diphenylphosphino)acridine-molybdenum tricarbonyl (17), compound 3 is capable of acting as a tridentate PNP ligand which coordinates transition metals in an approximately “T-shaped” planar coordination geometry. Single crystal X-ray structure analyses are reported for 3 and 17.

Bidentate phosphines of heteroarenes: 1,9-bis(diphenylphosphino)-dibenzothiophene and 4,6-bis(diphenylphosphino)dibenzothiophene

Abstract Twofold lithiation of dibenzothiophene with n-butyllithium and N,N,N′,N′-tetramethylethylenediamine (TMEDA) in boiling n-heptane followed by reaction with chlorodiphenylphosphine (Ph 2 PCl) yielded the title compounds 2 (colourless) and 3 (yellow). Both phosphine were characterised by single crystal X-ray structure analysis and 13 C, 1 H shift correlated 2D NMR spectroscopy, based on which our previous assignment of the yellow compound to structure 2 has to be revised.

Bidentate phosphines of heteroarenes: effective stabilization of the Co2(CO)6 fragment by 4,6-bis(diphenylphosphino) dibenzofuran☆

Reaction of Co2(CO)8 with 4,6-bis(diphenylphosphino)dibenzofuran (1) in diethylether gives the dinuclear complex 4,6-bis(diphenylphosphino)dibenzofurandicobalthexacarbonyl (2). The solid state structures of 1 and 2 have been established by X-ray crystallography. Low temperature 13C-NMR spectroscopy was used to analyse 2 in solution.

2,5,8,11,14,17-Hexa-t-butyldecacyclene and 1,7,13-/1,6,12-tri-t-butyldecacyclene: Possible precursors for bowl-shaped polycyclic arenes

Abstract Decacyclene (2) was converted into 2,5,8,11,14,17-hexa-t-butyldecacyclene (4) by Friedel-Crafts alkylation using t- butylchloride aluminium chloride in 1,2-dichlorobenzene. Dehydrogenating cyclotrimerization of 5-t-butylacenaphthene by reaction with elemental sulfur resulted in 1,7,13- and 1,6,12-tri-t-butyldecacyclene ( 6a 6b ) in the expected statistical 1:3 isomeric ratio. Single crystal X-ray structure analysis showed 4 to possess a non-planar, non-propeller Ct conformation in the crystal. According to molecular modelling (force field calculations) this non-propeller conformation is 12.7 kJ mol−1 higher in energy than the expected Dt propeller conformation. The observation of the energetically unfavourable non-propeller molecular conformation in the attributed to favourable crystal packing of the bulky t-butyl substituents.

(η12-[3.3]Paracyclopan)chrom(O) und (η12-[3.3]Paracyclophan) Chrom(I)Hexafluorophosphat☆

Zusammenfassung The title compounds 2 and 3 were synthesized and characterized.