03 Fakultät Chemie

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Open Access
1,2- and 1,3-diphosphetanes from alkylidenephosphines
(1983) Becker, Gerd; Becker, Winfried; Uhl, Gudrun; Uhl, Werner; Wessely, Hans-Jürgen
Alkyl- or arylbis(trimethylsilyl)phosphines as well as tris(trimethylsilyl)phosphine and the corresponding arsines react with acyl chlorides to give [1-(trimethylsiloxy)alkylidene]phosphines 1 and -arsines 2; most of their 2,2-dimethylpropylidene derivatives are thermally stable at room temperature. With the same class of phosphines as starting compounds and carbon disulfide [bis(trimethylsilylsulfano)methylidene]phosphines 3 are formed, whereas [(dialkylamino)methylidene]-4 and [diarylmethylidene]phosphines 5 or the corresponding arsines 6 and 7 can be obtained from acyl amides or ketones.
Open Access
(2, 2, 8, 8-Tetramethyl-5-oxa-4,6-diphospha-3, 6-nonadien)tetrakis[dicarbonyl-(methylcyclopentadienyl)mangan], der erste komplexierte Bis(phosphavinyl)ether
(1987) Ziegler, Manfred L.; Balles, Rainer; Nuber, Bernd; Becker, Gerd; Schmidt, Helmut; Kanellakopulos, Basil; Powietzka, Bernhard
Der Komplex eines neuartigen Liganden ist die Titelverbindung 1. Sie entsteht aus [(CH3C5H4)Mn(CO)2·thf] und (CH3)3C-C=P vermutlich unter H2O-Aufnahme. Im paramagnetischen Komplex 1 fungiert der Bis(phosphavinyl)ether als 8-Elektronendonor gegenüber den vier (CH3C5H4)Mn(CO)2-Einheiten.
Open Access
(2,2-Dimethylpropylidyne)phosphine
(1990) Becker, Gerd; Schmidt, Helmut; Uhl, Gudrun; Uhl, Werner
(2,2-Dimethylpropylidyne)phosphine is the first compound with a phosphorus-carbon triple bond stable at room temperature. Since the electronegativities of phosphorus (2.2) and carbon (2.5) differ substantially from the value of nitrogen (3.0), the compound is more likely to react as the analog of an alkine than of a nitrile. Thus far, the reactivity of the phosphine towards transition metal complexes with the metals in low oxidation states and towards organic 1,3-dipolar or Diels-Alder reagents, has been studied. With halides of main group and subgroup elements numerous insertion reactions have been observed; from the addition of lithium bis(trimethylsilyl)phosphide' 2tetrahydrofuran (THF) in 1,2-dimethoxethane (DME), lithium 3,5-di-tert-butyl-1, 2, 4-triphospholid' 3DME can be obtained.
Open Access
2,4-Bis(phenylimino)-1,3-diphosphetane aus Thiocarbamoyl- und Carbamoyltrimethylsilylphosphanen (Acyl- und Alkylidenphosphane ; 26)
(1985) Becker, Gerd; Härer, Jürgen; Uhl, Gudrun; Wessely, Hans-Jürgen
Die Bis(trimethylsilyl)phosphane R-P[-Si(CH3)3]2 1 (R = H3C a, H5C6 b, (H3C)3C c, H11C9 d) reagieren mit Phenylisothiocyanat zu Insertionsverbindungen, die sowohl in Lösung als auch im Festkörper [2] als [(N-Phenyl-Derivat 3-2b eliminiert in Gegenwart geringer Mengen an festem Natriumhydroxid, die tert-Butyl- 3-2c bzw. Mesityl-Verbindung 3-2d auch in Abwesenheit des Katalysators Bis(trimethylsilyl] sulfan; die zunächst gebildeten, instabilen [(Phenylimino)-methyliden]phosphane 6 dimerisieren rasch zu den in Lösung E/Z-isomeren 2,4-Bis(phenylimino)-1,3-diphosphetanen 7. Diese cyclischen Phosphane 7 sind über die NaOH-katalysierte Abspaltung von Hexamethyldisiloxan auch aus den Addukten 2 des Phenylisocyanats an Bis(trimethylsilyl)-phosphane 1 zugänglich. Die Temperaturabhängigkeit der NMR-Spektren wird am Beispiel des thermisch hinreichend stabilen tert-Butyl-Derivates 7c eingehend untersucht.
Open Access
A-type Ce2NCl3
(2011) Schurz, Christian M.; Schleid, Thomas
The crystal structure of cerium nitride chloride (A-type) as well as the synthesis method is described in this paper.
Open Access
About lanthanoid fluoride selenide oxoselenotantalates with the composition Ln3F2Se2TaO4 (Ln = La - Nd)
(2020) Grossholz, Hagen; Buyer, Constantin; Lotter, Sebastian M. A.; Wolf, Sarah; Schleid, Thomas
After solid-state reactions of the light lanthanoid metals, their oxides and fluorides as well as selenium in sealed tantalum ampoules with sodium chloride as a fluxing agent at 850 °C for 8 days needle-shaped single crystals of Ln3F2Se2TaO4 (Ln = La - Nd) were obtained. They crystallize in the orthorhombic space group Pnma analogous to La3F2Se2NbO4 with a = 1133-1120 pm, b = 400-393 pm and c = 1812-1778 pm (Ln = La - Nd) for Z = 4 as the first known quinary lanthanoid(III) oxoselenotantalates(V) with fluoride and selenide anions. The three crystallographically different Ln3+ cations are all surrounded by nine anions (O2-, F- and Se2-) each. Tantalum resides in an octahedral chalcogen coordination by forming trans-vertex oxygen-connected [TaO5Se]7- polyhedra, which build up chains 1∞{[TaOV2/2Ot3/1Set1/1]5-} along [010]. The sites of the four crystallographically different oxygen atoms and the two distinct fluoride anions were established by bond-valence calculations. One fluorine and three oxygen atoms are surrounded tetrahedrally by cations, while another fluoride and oxide anion exhibit just triangular non-planar coordination spheres. The two independent Se2- anions have five or six cationic neighbors.
Open Access
Activation of aromatic C-F bonds by a N‐heterocyclic olefin (NHO)
(2020) Mandal, Debdeep; Chandra, Shubhadeep; Neuman, Nicolás I.; Mahata, Alok; Sarkar, Arighna; Kundu, Abhinanda; Anga, Srinivas; Rawat, Hemant; Schulzke, Carola; Mote, Kaustubh R.; Sarkar, Biprajit; Chandrasekhar, Vadapalli; Jana, Anukul
A N‐heterocyclic olefin (NHO), a terminal alkene selectively activates aromatic C-F bonds without the need of any additional catalyst. As a result, a straightforward methodology was developed for the formation of different fluoroaryl‐substituted alkenes in which the central carbon-carbon double bond is in a twisted geometry.
Open Access
An acyclic diaminocarbene complex of platinum formed by desulfurization of 1,3‐bis(3‐methylpyridin‐2‐yl)thiourea
(2021) Bulak, Ece; Dogan, Ilknur; Varnali, Tereza; Schwederski, Brigitte; Gunal, Sule Erol; Lönnecke, Peter; Bubrin, Martina; Kaim, Wolfgang
The reaction of the ambidentate ligand 1,3‐bis(3‐methylpyridin‐2‐yl)thiourea (1) with [PtCl2(dmso)2] in dichloromethane led to formation of a poorly soluble compound 2, characterized as a conventional chelate complex [PtCl2(1)]=2. Reaction in methanol resulted in desulfurization to produce a fluorescing cationic diaminocarbene-platinum(II) complex 3, the structure of which was elucidated by X‐ray crystallography, mass spectrometry and NMR. Experimental findings were supported by DFT calculations.
Open Access
Acylphosphines and their derivatives with phosphorus atoms of coordination number 3, 2, and 1 (Acyl- and alkylidenphosphanes ; 21)
(1983) Becker, Gerd; Becker, Winfried; Mundt, Otto
The following article summarizes our work on acylphosphines and acylphosphides as well as on alkylidene- and alkylidynephosphines, most of which were thought only thirty years ago not to exist under ordinary conditions.
Open Access
Addition eines Phospha-alkins an Metall-Metall-Mehrfachbindungen
(1983) Becker, Gerd; Herrmann, Wolfgang A.; Kalcher, Willibald; Kriechbaum, Gangolf W.; Pahl, Claudia; Wagner, C. Thomas; Ziegler, Manfred L.
Im Kontext unserer Arbeiten über die Chemie von Metall-Metall-Mehrfachbindungen haben wir insbesondere im Hinblick auf mögliche Cycloadditions- und/oder Metathese-Reaktionen das nach Becker und Uhl bequem zugängliche 2,2-Dimethylpropylidinphosphan exemplarisch auf sein Verhalten gegenüber Metall-Metall-Mehrfachbindungen geprüft.
Open Access
Adducts of diaminophosphines with organoboranes
(2022) Dunaj, Tobias; Feil, Christoph M.; Nieger, Martin; Gudat, Dietrich
Reactions of chlorodiaminophosphines (R2N)2PCl (R=Et, iPr) with organoborohydrides M[BR′nH4‐n] (M=Na, Li; n=1-3; R′=alkyl, Ph, CN) proceed via H/Cl metathesis to furnish secondary phosphines and boranes which may either combine to afford isolable donor‐acceptor adducts (R2N)2P(H)-BR′nH3‐n, coexist without any sign of mutual interaction, or give rise to mixtures comprising both a labile phosphine borane and its constituents in a temperature dependent equilibrium. Stable phosphine complexes of BH2CN and BH2Ph react with KN(SiMe3)2 under PH‐bond metalation to afford spectroscopically detectable diaminophosphide boranes whose usability as nucleophilic building blocks is illustrated by trapping one specimen in a PC‐bond formation reaction with an alkyl halide. The selectivity of the individual H/Cl‐metathesis and electrophilic substitution steps as well as the thermal stability of the various reaction products depend subtly on the Lewis acidity of the borane fragment and on steric factors. Several complexes of (iPr2N)‐substituted phosphines with cyano‐ and phenylborane were characterized by single‐crystal XRD.
Open Access
Aging‐driven composition and distribution changes of electrolyte and graphite anode in 18650‐type Li‐ion batteries
(2022) Petz, Dominik; Baran, Volodymyr; Peschel, Christoph; Winter, Martin; Nowak, Sascha; Hofmann, Michael; Kostecki, Robert; Niewa, Rainer; Bauer, Michael; Müller‐Buschbaum, Peter; Senyshyn, Anatoliy
A series of low‐temperature studies on LiNi0.80Co0.15Al0.05O2 18650‐type batteries of high‐energy type with different stabilized states of fatigue is carried out using spatially resolved neutron powder diffraction, infrared/thermal imaging, and quasi‐adiabatic calorimetry. In‐plane distribution of lithium in the graphite anode and frozen electrolyte in fully charged state is determined non‐destructively with neutron diffraction and correlated to the introduced state of fatigue. An independent electrolyte characterization is performed via calorimetry studies on variously aged 18650‐type lithium‐ion batteries, where the shape of the thermodynamic signal is evolving with the state of fatigue of the cells. Analyzing the liquid electrolyte extracted/harvested from the studied cells reveals the decomposition of conducting salt to be the main driving factor for fatigue in the electrolyte degradation.
Open Access
Aktivierung von P-P-Bindungen in unsymmetrisch substituierten Diphosphanen
(2010) Hajdok, Imre; Gudat, Dietrich (Prof. Dr.)
Seit langem werden zweizähnige Liganden in der metallorganischen Chemie, der Koordinationschemie und der Katalyse angewendet. Für die Synthese solcher Liganden haben in neuerer Zeit Additionen an Alkene an Beachtung gewonnen, bei denen simultan zwei Donorgruppen in ein organisches Gerüst eingeführt werden. Mögliche Syntheserouten zu P,P-Donorliganden, die ebenfalls große Bedeutung haben, wurden in der doppelten Substitution 1,2-disubstituierter Olefine oder der Addition der P,P-Bindungen von Diphosphanen an Alkene oder Alkine gefunden. Unsere Gruppe hat unlängst N-heterocyclische Phosphane beschrieben, die sich durch außerordentlich reaktive P-P-Bindungen auszeichnen und mit Alkenen und Alkinen unter Phosphanylphosphanierung zu Hybrid-Bisphosphanen reagieren, die zwei Donorzentren mit unterschiedlichen elektronischen Eigenschaften aufweisen. Verbindungen dieses Typs stoßen auf reges Interesse als Liganden in der Katalyse. Ein Ziel dieser Doktorarbeit soll die Herstellung neuartiger N-heterocyclischer Diphosphane mit reaktiver P-P-Bindung sein, die anstelle eines Diazaphospholenrings aus acyclischen oder auch benzannellierten P-substituierten Diazaphospholen-Derivaten aufgebaut sind. Ziel ist hierbei, weitere Derivate mit polaren und damit reaktiven P-P-Bindungen aufzubauen, deren Donorzentren unterschiedliche stereochemische Eigenschaften haben. Ob die neuartigen Diphosphane P-P-Bindungspolarisation aufweisen und in Folge dessen eine reaktive P-P-Bindungen besitzen, wird am einfachsten durch Untersuchung des P-P-Abstands nachgewiesen. Deswegen ist es nötig, experimentelle Bestimmungen von P-P-Abständen dieser Verbindungen durch Röntgenstrukturuntersuchungen vorzunehmen, weshalb der Erhalt einkristalliner Proben der Zielverbindungen von entscheidender Bedeutung ist. Die Reaktivität der hergestellten Diphosphane gegenüber Alkenen und Alkinen soll untersucht werden. Die erhaltenen 1,2-Bisphosphane sollen in Bezug auf ihre Koordinationseigenschaften weiterhin eingehender durch die Herstellung von Metall-Komplexen untersucht werden. Hierbei wurde festgestellt, dass die Addition der P-P-Bindung an mono- oder disubstituierte Alkine regio- und Z-stereospezifisch unter Bildung eines einzigen Additionsprodukts abläuft. 1,2-Additionsreaktionen des Diphosphans an Fumarsäure-dimethylester beziehungsweise Maleinsäure-diethylester verliefen nicht stereospezifisch, sondern es wurden verschiedene Produkte erhalten. Eine cis-stereospezifische 1,2-Additionsreaktion war dagegen bei der Reaktion des Diphosphans mit Maleimid zu beobachten. Dies kann auf die starre Ringstruktur des Maleimids zurückgeführt werden. Von allen diesen Produkten wurden Komplexe erhalten.
Open Access
Alkaline metal intercalates of VSe2 by electrochemical intercalation
(2023) Kannen, Bastian; Rasche, Bertold
We report on the series of the alkali metal intercalates of VSe2 synthesised by electrochemical means in an aqueous environment. For all alkali metals we find water‐conintercalated structures (stage I and stage II), of which only the sodium structure had been reported so far. The new structures are analyzed by powder X‐ray diffraction and Rietveld refinement. Their (meta‐)stability is investigated in terms of the open circuit potential, revealing the sensitivity towards oxygen. Except for the lithium intercalate these structures transform into water‐free alkali metal intercalates under vacuum. In addition, scanning electron microscopy reveals the impact of different electrochemical intercalation techniques yielding different intercalation rates. This paves the way for future single crystal investigations.
Open Access
Alkylidenephosphines and diphosphetanes
(1987) Becker, Gerd; Becker, Birgit; Becker, Winfried; Uhl, Werner
In studies of the reactivity and thermal stability of various alkylidenephos-phines prepared from benzophenone and organylbis(trimethylsilyl)phosphines via a NaOH-catalyzed elimination of hexamethyldisiloxane (eq. la), detailed analyses of nmr-spectra and x-ray structure determinations prove the methyl derivative la to dimerize to an 1,3-diphosphetane (2a), whereas from the iso-propyl compound 1b the 1,2-diphosphetane 2b is obtained [1]. This observation confirms our hypothesis that the formation of 1,2- or 1,3-diphosphetanes is determined by the steric requirements of the substituent at phosphorus.
Open Access
Alkylidynephosphines : syntheses and reactivity
(1987) Becker, Gerd; Becker, Winfried; Knebl, Robert; Schmidt, Helmut; Hildenbrand, Ute; Westerhausen, Matthias
In the past, different methods have been utilized for the preparation of alkylidynephosphines. Whereas, however, small amounts of thermally instable derivatives might be obtained from reactions in the gas phase, the synthesis of phosphines which are stable under an inert atmosphere, as for instance those with a tert-butyl or a 1-adamantyl substituent at the carbon atom of the PEC group, is best started with tris (trimethylsilyl) phosphine itself or with the more reactive lithium bis (trimethylsilyl) phosphide.2 tetrahydrofuran complex. Treatment of either compound with acyl halides results in the formation of acylbis (trimethylsilyl) phosphines which, at room temperature, rearrange to the corresponding trimethylsilyl [1-(trimethylsiloxy) alkylidene] isomers. As traces of hydrogen halide accelerate the conversion of tris (trimethylsilyl) phosphine to the triacyl derivatives, the use of the lithium phosphide is strongly recommended in all cases where impure acyl halides are used. In the presence of small amounts of solid sodium hydroxide suspended in an etherial solvent, the thus prepared trimethyl[1-(trimethylsiloxy)-alkylidene]phosphines eliminate hexamethyldisiloxane to yield the required alkylidyne compounds. Running the decomposition without a solvent at a higher temperature, Regitz and coworkers were able to improve this method further.
Open Access
Annellated 1,3,4,2-triazaphospholenes-simple modular synthesis and a first exploration of ligand properties
(2022) Richter, Ferdinand; Birchall, Nicholas; Feil, Christoph M.; Nieger, Martin; Gudat, Dietrich
The successful use of 1,3,4,2-triazaphospholenes (TAPs) as organo-catalysts stresses the need for efficient synthetic routes to these molecules. In this study, we establish the [1 + 4]-cycloaddition of PBr3 to azo-pyridines as a new approach to preparing pyrido-annellated TAPs in a single step from easily available precursors. The modular assembly of the azo-component via condensation of primary amines and nitroso compounds along with the feasibility of post-functionalization at the P-Br bond under conservation of the heterocyclic structure allows, in principle, to address a wide range of target molecules, which is illustrated by prototypical examples. The successful synthesis of a transition metal complex confirms for the first time the ability of a TAP to act as a P-donor ligand. Crystallographic studies suggest that hyperconjugation effects and intermolecular interactions induce a qualitatively similar ionic polarization of the P-Br bonds in TAPs as in better known isoelectronic diazaphospholenes.
Open Access
Anwendungsnahe Untersuchungen von Elektrodenmaterialien in Lithium-Ionen-Batterien
(2016) Birkenmaier, Claudia; Schleid, Thomas (Prof. Dr.)
Open Access
Approaching dissolved species in ammonoacidic GaN crystal growth: a combined solution NMR and computational study
(2020) Becker, Peter; Wonglakhon, Tanakorn; Zahn, Dirk; Gudat, Dietrich; Niewa, Rainer
Open Access
Azide‐substituted 1,2,3‐triazolium salts as useful synthetic synthons : access to triazenyl radicals and Staudinger type reactivity
(2023) Stein, Felix; Suhr, Simon; Singha Hazari, Arijit; Walter, Robert; Nößler, Maite; Sarkar, Biprajit
Mesoionic carbenes (MIC) are a popular class of compound that are heavily investigated at the moment. The access to cationic MICs, and the ability of MICs to stabilize radicals are two highly attractive fields that have hardly been explored until now. Here the synthesis and characterisation of three different cationic azide-substituted 1,2,3-triazolium salts, used as building blocks for studying their reactivity towards triphenylphosphine are reported, where the reactivity is dependent on the nature of the starting triazolium salt. Furthermore, the cationic triazolium salts were used to develop a series of unsymmetrical MIC-triazene-NHC/MIC’ compounds, which can be readily converted to the radical form either by electrochemical or chemical methods. These radicals, which display NIR electrochromism, were investigated using a battery of techniques such as electrochemistry, UV/Vis/NIR and EPR spectroelectrochemistry, and theoretical calculations. Interestingly, the MIC plays an important role in the stabilization of the triazenyl radical, particularly in a competitive role vis-à-vis their NHC counterparts. These results shed new light on the ability of MICs to stabilize radicals, and possibly also on their π-accepting ability.