bluuebunny/crossref_metadata_2025_split huggingface dataset:
“Yeah, but I’m Shy!”: Classroom Participation as a Social Justice Issue
Authors: DiAngelo Robin , Sensoy Özlem 
Published: August 2018

Abstract
In-class participation is a common component of many university students’ course grade, yet there has been some debate over whether it is fair to grade participation, given that some students are “ naturally” introverted. In this paper, we problematize the central assumption that the arguments against grading participation rest upon: that classrooms are neutral spaces into which a range of personalities come together, each with unique needs that should be recognized and supported. As educators whose work and teaching is grounded in critical social justice frameworks, we argue that there is a fundamental dynamic that is missed when silence is presumed to be a-political. We argue that classrooms are microcosms of the wider society and as such, are political spaces in which dynamics of unequal social power also play out; there is no neutral classroom or natural mode of engagement. In this paper, we lay out the foundation of a social justice approach to teaching and problematize the notion of neutral classroom spaces. We speak back to some of the most common arguments against grading classroom participation and in doing so argue that participation in classroom settings is a central element to dismantling social injustice in our wider communities.
Cytologische Studien IV
Authors: Wohlfarth-Bottermann K. E. 
Published: August 2018

An Hand von Dünnschnitten läßt sich im Endoplasma von Paramecium caudatum unter bestimmten experimentellen Bedingungen eine Entstehung von Mitochondrien aus cytoplasmatischen Strukturen nachweisen. Kleine „cytoplasmatische Bläschen“ vergrößern sich und bilden die für die Mitochondrien von Paramecium typischen Innenstrukturen aus. Die Ausbildung dieser Innenstrukturen, der Tubuli mitochondriales, wird eingeleitet durch das Auftreten von Mikrotubuli, deren Durchmesser nur etwa die Hälfte des Durchmessers normaler Tubuli beträgt. Auf dem Wege zur Zellperipherie wachsen diese „Promitochondrien“ mit Mikrotubuli zu normalen Mitochondrien heran.
In der Zellperipherie von Paramecium vermehren sich die Mitochondrien durch Querteilung. Eine gleichmäßige Verteilung der Mitochondrien-Substanz auf die beiden Tochterstadien wird hierbei nicht beobachtet.
Bei den Paramecium-Mitochondrien läßt sich eine Abscheidung von Tubuli mitochondriales in das Cytoplasma nachweisen. Es handelt sich um eine echte Abscheidung geformter Sekrete durch die Mitochondrien, da diese die abgegebenen tubulären Strukturen regenerieren können. Die Neubildung der Tubuli beginnt wie bei der Entstehung der Mitochondrien mit den zuerst auftretenden Mikrotubuli.
Autoradiographische Untersuchungen über den Eiweißstoffwechsel von Oocyten und Eizellen
Authors: Erb Walter , Maurer Werner 
Published: August 2018

Bei Oocyten und Eizellen von Seeigeln sowie bei Oocyten von Seesternen und bei pflanzlichen Eizellen zweier Braunalgen-Arten wurde die Eiweißsynthese innerhalb der verschiedenen Zellstrukturen mit 3H-Lysin und 3H-Leucin autoradiographisch untersucht. Beim Seeigel können solche Untersuchungen unter in vivo-Bedingungen durchgeführt werden.
Auch unter in vivo-Verhältnissen konnte die Bedeutung des Nucleolus für die Kerneiweiß-Synthese bei Oocyten bestätigt werden. Der Beitrag des Nucleolus zur Kerneiweiß-Synthese ist bei Oocyten wesentlich größer als bei somatischen Zellen. Innerhalb der Zellstrukturen war die Aminosäure-Inkorporation pro Volumen-Einheit unabhängig von der Größe der Strukturen bzw. dem Entwicklungsstadium dieser Zellen. Die Eizellen der Seeigel zeigten keine Aminosäure-Inkorporation. Bei den Eizellen der beiden Fucus-Arten dominiert die Inkorporation im Cytoplasma.
Preparation and Characterization of Group III A Derivatives
Authors: Pohlmann J. L. W. , Brinckmann F. E. 
Published: August 2018

Unter Verwendung des Grignard - Reagenz von Brompentafluorbenzol wurde die vollständige Reihe der Tris-(pentafluorphenyl)-Verbindungen der Elemente der dritten Hauptgruppe in siedendem Toluol dargestellt und in Form der Ätherate charakterisiert. Bei der Sublimation ergaben die Bor- und die Thallium-Verbindungen die freien Derivate. Hingegen gelang es nicht, den 1 : 1-Ätherkomplex von Tris-(pentafluorphenyl)-aluminium zu spalten; ebenso schlugen alle Versuche fehl, die ätherfreie Verbindung direkt darzustellen.
Bei der Bereitung der Indium- und der Thallium-Derivate aus den Chloriden wurden die entsprechenden Bis-(pentafluorphenyl)-metallbromide als Nebenprodukte isoliert. Demnach muß ein Halogenaustausch mit der Arylierung in Konkurrenz stehen, da bei der Verwendung von Indiumtribromid nur Bis-(pentafluorphenyl)-indiumbromid erhalten wurde.
Bei den meisten Umsetzungen trat ein fluorhaltiger, aromatischer Kohlenwasserstoff als weiteres Nebenprodukt auf; derselbe wurde auch direkt aus Pentafluorphenylmagnesiumbromid in siedendem Toluol erhalten.
Polymerisation von Methacrylsäuremethylester unter stiller elektrischer Entladung
Authors: Strohmeier W. , Grübel H. 
Published: August 2018

Reiner Methacrylsäuremethylester (MM) kann unter stiller elektrischer Entladung bei Temperaturen polymerisiert werden, bei welchen eine thermische Polymerisation nicht möglich ist. Das gleiche gilt für MM, welchem Metallcarbonyle zugesetzt sind.
Zugabe von Metallcarbonylen und Tetrachlorkohlenstoff zu MM ermöglicht die entladungschemische Polymerisation bei 50° mit hohen Ausbeuten unter Bildung hochmolekularer Produkte.
II. The Photo-electric Efficiency of the Median and the Lateral Photoreceptor of the Barnacle Balanus eburneus
Authors: Krischer Christof C. 
Published: August 2018

Formulae which were derived in a preceeding publication are used to analize the electrical response to flashes of 10 μsec duration of the median, Fig. 3, and the lateral photoreceptors of the barnacle Balanus eburneus in the temperature ranges 3 - 5°, 12 - 14° and 20 - 22°C. The method of measuring nerve current extracellularly is applied and discussed.
The median receptor has a response rate two times faster than the lateral receptor. The curve parameters of both receptors such as peak amplitude, latency time and initial potential increase with time obey, however, the same dependence of light intensity and temperature, provided they are normalized to the same state (halfsaturation), Figs. 4, 6, 7, Table III. With the macroscopic morphology and the electrophysiological data the photo-electric efficiency, defined as the number of univalent ions which flow across the receptor membrane for each absorbed photon, is for both receptors about 105. A complementary discussion accounting for the light-reflecting tapetum of the lateral receptor and the larger inner surface area of the median receptor yields for the median receptor a higher efficiency for flashes and a smaller efficiency for steady light. The reverse holds for the lateral receptor. A model explains this specialization of the photoreceptors with a difference in volume of the photopigment-bearing structures (microvilli).
Synthesis of 6-, and 7-Nitro-1,2-di-oxo-4-thioindeno[2,3,d] Pyrimidines
Authors: El-Zimaity Mohamed Tawfik , Kandeel Ezzat Mohamed , El-Morsi Saad , Elnagdi Mohamed Hilmy 
Published: August 2018

Ethyl 5-nitroindan-1,3-dione-2-carboxylate (3; 5-NO2) was prepared via esterification of 3-nitrophthalic acid and subsequent treatment of the resulting diester with ethyl acetate in sodium ethoxide solution. Attempted synthesis of 3; 4-NO2 via a similar route was obscured by unability to effect diesterification of 1: 3-NO2 by ethanol and hydrochloric acid. The diester 2: 3-NO2 could be prepared by the action of ethanol on the anhydride 5. This ester could be then converted into 3: 4-NO2 by treatment with ethyl acetate and sodium ethoxide.
Compounds 3 (4- and 5-NO2) could be converted into the corresponding indeno[2,3-d]-pyrimidine derivatives (9 a, b) by their reaction with thiourea. The behaviour of 9 a, b toward the action of hydrazinehydrate, monochloroacetic acid and hydrogen peroxide is reported.
Eine theoretische Begründung empirischer Sektorenregeln der optischen Aktivität / Theoretical Verification of Empirical Sector Rules of Optical Activity
Authors: Rau Hermann , Schuster Otto 
Published: August 2018

Abstract
A simple procedure for derivation of octant rules for optically active molecules containing a chromophoric group is developed within the framework of Kuhn's classical model of coupled oscillators. The important feature in this derivation is the clue that the locus of the center of gravity of the atoms not belonging to the chromophoric group and the direction of maximum polarizability of this ensemble of atoms are not independent. The octant rule for carbonyl compounds arrived at by this procedure is in agreement with the empirical one. A newly derived rule for cis-azo compounds is verified by empirical data.
Komplexe zweifach positiver Übergangsmetallkationen mit Hydrazido-thiophosphorsäure-estern/ Complexes of Divalent Transition Metals with Hydrazido Thiophosphoric Acid Esters
Authors: Engelhardt Udo , Friedrich Bernd , Kirner Ingeborg 
Published: August 2018

Abstract
Dihydrazido thiophosphoric acid phenyl ester, (NH2NH)2P(= S)-OC6H5 (DHTPPH), forms a 2:1 complex with manganese(II) chloride: [Mn(II)(DHTPPh)2Cl2], soluble in methanol. Solvolysis yields the corresponding methyl ester complex. With water in methanol the dihydrazidothiophosphato complex [Mn(II){(NH2NH)2P(= O)S}2] is formed. Monohydrazido thiophosphoric acid diphenyl ester NH2NH-P(= S)(OC6H5)2 (MHTPPh) gives various complexes with first row transition metals: [M(II)(MHTPPh)nX2], n = 2, 4; X = halogen. The nickel complex (n = 4; X = Cl) is characterized by elemental analysis and spectroscopic methods. MHTPPh is monodentate through the terminal N atoms of the hydrazido groups. Iron(II) and cadmium complexes have different compositions (n- 2; X = Cl) and therefore different structures, probably with MHTPPh as a bidentate chelate ligand.
Beiträge zur Chemie des Bors, 163 [1]. Die Molekülstruktur zweier Silaborazine / Contributions to the Chemistry of Boron, 163 [1]. The Molecular Structure of Two Silaborazines
Authors: Hanecker E. , Nöth H. 
Published: August 2018

Abstract
The crystal and molecular structure of Ph2Si(NMeBMe)2NMe (1) and MeB(NMeSiPh2 )2NMe (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 ( 1H, 11B, 13C, 27Si) are consistent with planar silaborazine rings.
Synthese unsymmetrischer Trissilylamine mit gehinderter Bindungsrotation / Synthesis of Unsymmetrical Trissilylamines with Rotational Barrier
Authors: Walter Simone , Klingebiel Uwe , Noltemeyer Mathias , Schmidt-Bäse Dieter 
Published: August 2018

Bis- and tris(fluorosilyl)amines with bulky groups are prepared in the reaction of lithiated di-tert-butylfluorosilylamine with fluorosilanes. Tris(fluorosilyl)amines with three different silyl groups could be synthesized stepwise in these reactions.
In all tris(fluorosilyl)amines a rotational barrier is observed by NMR spectroscopy at room temperature. The compounds 7, 8, 11 and 12 show only one structural isomer, whereas the compounds 10, 13 and 14 show two structural isomers. To prove the conclusion drawn from the spectra, the crystal structures of 10 and 12 were determined.
Die Kristallstrukturen von [MoCl2(NO)2(OPEt3)]2, [MoCl3(NO)(OPPh3)2•MoCl4(OPPh3)2], [MoCl2(NO)(PPh3)2(CH3CN)] und [MoCl4(NPPh3)(OPPh3)] / The Crystal Structures of [MoCl2(NO)2(OPEt3)]2, [MoCl3(NO)(OPPh3)2 • MoCl4(OPPh3)2], [MoCl2(NO)(PPh3)2(CH3CN)], and [MoCl4(NPPh3)(OPPh3)]
Authors: Philipp Gunnar , Wocadlo Sigrid , Massa Werner , Dehnicke Kurt , Fenske Dieter , Maichle-Mössmer Cäcilia , Niquet Elke , Strähle Joachim 
Published: August 2018

The title compounds have been prepared by reactions of MoCl2(NO)2 with PPh3, OPPh3, or Me3SiNPR3 (R = Et, Ph) in dichloromethane and acetonitrile suspension, respectively. All complexes were characterized by IR spectroscopy and by crystal structure determinations. [MoCl2(NO)2(OPEt3)]2: Space group C2/c, Z = 4, 2950 observed unique reflections, R = 0.029. Lattice dimensions at —70 °C: a = 2390.5(11), b = 875.5(5), c = 1399.1(6) pm, β = 113.18(2)°. The complex forms a centrosymmetric dimer with MoCl2Mo bridges, the nitrosyl groups being in a cis-arrangement. The OPEt3 ligand is coordinated in trans position to one of the nitrosyl ligands.
[MoCl3(NO)(OPPh3)2 • MoCl4(OPPh3)2]: Space group P21/c, Z = 4, 10243 observed unique reflections, R = 0.060. Lattice dimensions at —60 °C: a = 1900.4(3), b = 1689.1(5), c = 2209.3(7) pm, β = 95.92(2)°. The structure consists of the two independent complexes [MoCl3(NO)(OPPh3)2] and [MoCl4(OPPh3)2]. In both complexes the OPPh3 groups are in a cis-arrangement at the octahedrally coordinated Mo atoms; in the nitrosyl complex one of the OPPh3 molecules is in trans-position to the nitrosyl ligand.
[MoCl2(NO)(PPh3)2(CH3CN)]: Space group P21/n, Z = 4, 5107 observed unique reflections, R = 0.028. Lattice dimensions at 20 °C: a = 1006.5(2), b = 1527.2(2), c = 2342.3(2) pm, β = 90.97(1)°. The PPh3 molecules are in trans-positions to one another at the octahedrally coordinated Mo atom, whereas the acetonitrile molecule is in trans-position to the nitrosyl ligand.
[MoCl4(NPPh3)(OPPhi)]: Space group P21, Z = 2, 3323 observed unique reflections, R = 0.057. Lattice dimensions at —70 °C: a = 985.7(8), b = 1471.2(9), c = 1215.9(11) pm, β = 100.50(3)°. The OPPh3 molecule coordinates in trans-position to the phosphorane iminato ligand at the octahedrally coordinated Mo atom.
Darstellung, 11B-NMR- und Schwingungsspektren von Aminohexahydro-closo-hexaborat(1–), [B6H6(NH2)]- sowie Kristallstruktur von Cs[B6H6(NH2)] · H2O / Preparation, 11B NMR and Vibrational Spectra of Aminohexahydro-closo-hexaborate(1–), [B6H6(NH2)]-, and the Crystal Structure of Cs[B6H6(NH2)] · H2O
Authors: Franken A. , Preetz W. 
Published: August 2018

Aminohexahydro-closo-hexaborate(1–), Crystal Structure, 11B NMR Spectra, Vibrational Spectra
By reduction of [B6H5(NO2)]2- with Fe2+ in aqueous alkaline solution [B6H6(NH2)]- is formed. The compound has been separated by extraction with dichloromethane in the presence of tetrabutylammoniumbromid and precipitated from the organic phase by adding CsCH3COO/C2H5OH. The Crystal structure of Cs[B6H6(NH2)] · H2O has been determined by single crystal X-ray diffraction analysis; monoclinic space group C2 with a = 22.1075(14), b = 6.491(2), c = 5.9570(4) A, β = 100.168(6)°. The 11B NMR spectrum is consistent with a mono-hetero-substituted octahedral B6 cage with local C4v symmetry. The IR and Raman spectra exhibit characteristic N–H, B–H and B6 vibrations.
Preparation and Crystal Structures of the Ternary Compounds Ag2SiP2 and AuSiP
Authors: Kaiser Peter , Jeitschko Wolfgang 
Published: August 2018

Abstract
The title compounds were prepared by solid state reaction of the elemental components. Their crystal structures were determined from single-crystal X-ray diffractometer data. Ag2SiP2: 14̄2d, a = 652.75(5) pm, c = 855.0(1) pm, Z = 4, R = 0.024 for 611 structure factors and 14 variable parameters; AuSiP: R3m, a = 345.9(1) pm, c = 1720.0(3) pm, Z = 3, R = 0.023 (352 F values, 11 variables). The silicon atoms in Ag2SiP2 are tetrahedrally coordinated by phosphorus atoms. The compound might therefore be considered as a phosphidosilicate and its formula can be rationalized as (Ag+1)2Si+4(P-3)2. However, Ag2SiP2 is not a tetrahedral compound since the phosphorus atoms have five near neighbors (3Ag + 2Si) and the silver atoms are coordinated by three phosphorus atoms in almost trigonal planar coordination. Weak silver-silver bonding is assumed for the shortest Ag-Ag contacts of 318 pm. In AuSiP the gold atoms are in a linear coordination of one silicon (235.5 pm) and one phosphorus atom (232.6 pm). The silicon and phosphorus atoms are tetrahedrally coordinated (3Si + 1 Au and 3P + 1 Au, respectively). Thus, the elements can be assigned oxidation numbers according to the formula Au+1Si+2P-3 . This structure was also refined in the centrosymmetric space group R3̄m, but in this improper setting the silicon and phosphorus atoms occupy one crystallographic site with random occupancy.
Metallkomplexe von Farbstoffen, VIII [1]. Ein- und zweikernige Palladium- und Platin(II)-Chelat-Komplexe mit dem Mono- und Dianion von Indigo und Indigoderivaten / Metal Complexes of Dyes, VIII [1]. Mono- and Dinuclear Palladium and Platinum (II) Chelate Complexes of the Mono- and Dianion of Indigo and Derivatives thereof
Authors: Lenz Andreas , Schmidt Christoph , Lehmann Annette , Wagner Barbara , Beck Wolfgang 
Published: August 2018

Abstract
A series of mono and bis N,O-chelate complexes 1-32 with the mono and dianion of indigo and indigo derivatives (R3P)(C1)M(L-H+) (M = Pd,Pt), (n3-allyl)Pd(L-H+), (Ph2C=NCH2CO2Et-H+)Pd(L-H+), (PhN=NPh-H+)Pd(L-H+), (C5H5)Fe(C5H3CH2NMe2)Pd(L-H+), [(R3P)(Cl)Pt]2(L-2H+), [(n3-allyl)Pd]2(L-2H+), [(C6H4CH2NMe2)Pd]2(L-2H+) with L = indigo, 4,4′-dichloro-, 6,6′-dichloro-, 6,6′-dibromo-, 6,6′-di-nBu-, 4,4′-dichloro-, 5.5′dibromo-, 5,5′, 6,6′-tetramethoxy-, 4.4′-di-S12H25-, 5,5′-di-SO3Na- indigo, indigo malonic ester and tetrahydro indigo have been prepared from chloro bridged metal complexes. In comparison to the free neutral indigo ligands the complexes show a high bathochromic shift in the VIS spectra (150-300 nm) which is mainly due to the anionic character of the coordinated indigo ligands. The structure of [(Et3P)(Cl)Pt]2(indigo-2H+) has been determined by X-ray diffraction.
Röntgenstrukturanalyse von zwei Verbindungen des Kupfertyps BaMLn2O5 (M = Zn, Ln = Sm, Tm) und von BaSmAIZn3O7 / X-Ray Analysis of Two Compounds of the Copper Type BaMLn2O5 (M=Zn, Ln=Sm, Tm) and of BaSmAlZn3O7
Authors: Rabbow Ch. , Panzer S. , Müller-Buschbaum Hk. 
Published: August 2018

Abstract
Kupfertyps BaMLn2O5 (M=Zn, Ln=Sm, Tm) und von BaSmAIZn3O7 X-Ray Analysis of Two Compounds of the Copper Type BaMLn2O5 (M=Zn, Ln=Sm, Tm) and of BaSmAlZn3O7 The barium zinc lanthanoide oxides BaZnSm2O5 (I) and BaZnTm2O5 (II) crystallize in the BaCuLn2O3 copper type with orthorhombic symmetry, space group D16
2h,Pnma, (I)
a = 12.575(2), b = 5.804(1), c = 7.198(1) Å and (II):
a = 12.258(2), b = 5.684(1), c = 7.010(2) Å, Z = 4. Zinc shows square pyramidal oxygen coordina­ tion, but the strong elongation of the CuO5 pyramid in the copper type is missing. BaSmAlZn3O7 crystallizes in the space group C4
6V-P63mc, a = 6.346(1), c = 10.237(3) Å, Z = 2. The metal coordination of oxygen and the shifts of the ratio Al : Zn at the sites (6c) and (2a) depending on the size of the lanthanoid ions are discussed.
Metal-Mediated Assembly of Hexameric Ethylcycloarsoxane (C2H5AsO)6 in Mono-and Dinuclear Complexes with Tetrahedral and Octahedral Coordination Spheres
Authors: Häusler Thomas , Sheldrick William S. 
Published: August 2018

Abstract
A metal-assisted ring expansion from the preferred solution species (EtAsO)n, n = 3,4, to the hexameric ligand (EtAsO)6 is observed for the reactions of [ReBr(CO)5], [RuCL2(Ph3P)3], RhCl3 ·3H2O and [Cu2CF3SO3)2(C6H6)] with ethylcycloarsoxane. Whereas two metal frag­ments are facially coordinated by the upper and lower three As atoms of a flattened As6O6 cuboctahedron in both [{ReBr(CO)2}2 {μ-[cyclo-(EtAsO)6]}] (1) and [Cu2{μ-[cyclo-(EtAsO)6]}(Me2PhP)2](CF3SO3)2 (4), potential ring strain restricts the reaction with the other compounds to the formation of mononuclear complexes [RuCl2{cyvclo-(EtAsO)6}(Ph3P)] (2)and [RhCl3{cyclo-(EtAsO)6}] (3) with k3As1,3,5 coordination. The structures of 1 - 4 were established by X-ray structure analysis. A shift in the ν(As-O) IR absorption bands to higher wavenumbers (830 - 788 cm-1 ) is characteristic for (EtAsO)6 complexes in comparison to those of the cyclic tetramer (781-747 cm-1 ).
Synthese von Bis[pyridin-phthalocyaninato(1,5-)iridium(II)]iodid und Pyridin-iodo-phthalocyaninato(2-)iridium(III)-Pyridin durch schrittweise Oxydation von Bis[pyridin-phthalocyaninato(2-)iridium(II)]/Synthesis of Bis[pyridine-phthalocyaninato(1,5-)iridium(II)] Iodide and Pyridine-iodo-phthalocyaninato(2-)iridium(III)-Pyridine by Successive Oxidation of Bis[pyridine-phthalocyaninato(2-)iridium(II)]
Authors: Hückstädt Heiner , Homborg Heiner 
Published: August 2018

Abstract
Successive oxidation of bis[pyridine-phthalocyaninato(2-)iridium(II)] with iodine first yields mixed-valent bis[pyridine-phthalocyaninato(1,5-)iridium(II)] iodide ([(Ir(py)pc1.5-}2]I) and then pyridine-iodo-phthalocyaninato(2-)iridium(III)-pyridine ([Ir(py)(I)pc2-]·py). The latter crystallizes monoclinically with the following cell parameters: a = 10.258(1) Å, b = 17.589(3) Å, c = 19.723(2) Å, β = 92.95(1)°, space group P21/n, Z = 4. IrIII is in the centre of a slightly distorted pc2- ligand and coordinates pyridine and iodide in a trans-arrangement. The average Ir-Niso distance is 1.995(5) Å (Niso: isoindole N atom), the Ir-Npy and Ir-I distan­ces are 2.102(5) and 2.657(1)Å, respectively. By a similar oxidation of [{Rh(py)pc2- }2] only [Rh(py)(I)pc2- ]·py is obtained. Solid state spectral properties with diagnostic absorption bands at 1360. 1456, 5620 and 19800 cm-1 confirm the mixed-valent diphthalocyaninate(1.5-).
The Thermal Isomerization of a Tetrahydro-2,3-disilanaphthalene into a 1,2-Disilacyclobutane -The Conversion of a Formal Silene [2+4] Cyclodimer into the [2+2] Cycloadduct
Authors: Krempner Clemens , Kempe Rhett , Oehme Hartmut 
Published: August 2018

Abstract
1,2,3,8a-Tetrahydro-1 -mesityl-5,7,8a-trimethyl-2,2,3,3-tetrakis(trimethylsilyl)-2,3-disilanaphthalene (3), the formal [2+4] cyclodimer of the transient 2-mesityl-1,1-bis(trimethylsilyl)-silene (2), on thermal treatment gradually isomerizes to give a mixture of the [2+2] products (E)-and -predominantly -(Z)-3,4-dimesityl-1,1,2,2-tetrakis(trimethylsilyl)-1,2-disilacyclo-butane [(E/Z)-4], By prolonged heating or at higher temperatures both (E/Z)-3 and (Z)-4 are converted into (E)-4, the thermodynamically most stable head-to-head dimer of 2. Possible pathways of the isomerization processes are discussed.
Hydrogenation of Toluene over La0.8Sr0.2Fe1-xCoxO3-z Perovskite Catalysts
Authors: Schinzer Carsten , Saymeh Riyadh A , Asfour Hassan M 
Published: August 2018

Abstract The hydrogenation of toluene over perovskites of composition La0.8Sr0.2Fe1-x CoxO3-z (x = 0.0, 0.2, 0.5, 0.8 and 1.0) is reported. The catalyst material has been prepared by the coprecipitation method using maleic acid as the complexing agent. The activity for the gas phase reaction of toluene and hydrogen at temperatures between 50 °C to 300 °C is reported for as-prepared and activated materials. The conversion has been found to be nearly temperature-independent over the as-prepared-per­ ovskites with a maximum of 40% conversion found for a composition La0.8Sr0.2Fe0.5Co0.5O2.86. Activation by an oxygen treatment at 500 °C was successful to enhance the activity of the Co-rich perovskites. All of these catalysts show a complete conversion of toluene at 100 °C, but activity decreases by time due to a reduction of the catalyst material. Again, La0.8Sr0.2Fe0.5Co0.5O2.86 exhibits the slowest loss of activity. A model for its special properties is mainly attributed to the p-type conduction behaviour. The conversion behaviour of the perovskite type catalysts investigated here is compared to the results obtained with noble-metal supported catalysts and it can be concluded, that the perovskites exhibit higher conversion rates, maximum temperatures and higher cracking onset temperatures than these.