Christian Kuntz
University of Regensburg
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Featured researches published by Christian Kuntz.
Angewandte Chemie | 2009
Manfred Scheer; Christian Kuntz; Markus Stubenhofer; Michael Linseis; Rainer F. Winter; Marek Sierka
Radically complex: The photolytic reaction of [Cp*P{W(CO)(5)}(2)] (Cp* = C(5)Me(5)) with a diphosphene produces, via a radical intermediate, an air-stable complexed triphosphaallyl radical, in which the unpaired electron is evenly distributed over both terminal P atoms. Oxidation of the radical leads to a triphosphaallyl cation, which is only stable at low temperatures in solution, whereas the stable triphosphaallyl anion is formed by reduction (see picture, Mes* = 2,4,6-tri-tert-butylphenyl).
Angewandte Chemie | 2010
Manfred Scheer; Christian Kuntz; Markus Stubenhofer; Manfred Zabel; Alexey Y. Timoshkin
Stepwise opening and final removal of the η1-bound Cp* substituents in the bridged pentelidene complexes [Cp*E{W(CO)5}2] (E=P, As) occurs by the reaction with primary phosphines. Not only novel diphospha- and arsaphosphanorbornenes are obtained, but also diastereomerically pure complexed triphosphines. All reaction steps were monitored by NMR spectroscopy, and compounds structurally characterized.
Chemistry: A European Journal | 2008
Manfred Scheer; Daniel Himmel; Christian Kuntz; Shuzhong Zhan; Eva Leiner
Thermolysis of [Cp*P{W(CO)5}2] (1) in the presence of [{CpMo(CO)2}2] leads to the novel complexes [{(CO)2Cp*W}{CpMo(CO)2}(micro,eta2:eta1:eta1-P2{W(CO)5}2)] (6; Cp=eta5-C5H5, Cp*=eta5-C5Me5), [{(micro-O)(CpMoWCp*)W(CO)4}{micro3-PW(CO)5}2] (7), [{CpMo(CO)2}2{Cp*W(CO)2}{micro3-PW(CO)5}] (8) and [{CpMo(CO)2}2{Cp*W(CO)2}(micro3-P)] (9). The structural framework of the main products 8 and 9 can be described as a tetrahedral Mo2WP unit that is formed by a cyclisation reaction of [{CpMo(CO)2}2] with an [Cp*(CO)2W[triple chemical bond]P-->W(CO)5] intermediate containing a W--P triple bond and subsequent metal-metal and metal-phosphorus bond formation. Photolysis of 1 in the presence of [{CpMo(CO)2}2] gives 8, 9 and phosphinidene complex [(micro3-PW(CO)5){CpMo(CO)2W(CO)5}] (10), in which the P atom is in a nearly trigonal-planar coordination environment formed by one {CpMo(CO)2} and two {W(CO)5} units. Comprehensive structural and spectroscopic data are given for the products. The reaction pathways are discussed for both activation procedures, and DFT calculations reveal the structures with minimum energy along the stepwise Cp* migration process under formation of the intermediate [Cp*(CO)2W[triple chemical bond]P-->W(CO)5].
Angewandte Chemie | 2015
Michael Seidl; Christian Kuntz; Michael Bodensteiner; Alexey Y. Timoshkin; Manfred Scheer
The reaction of the phosphinidene and arsinidene complexes [Cp*E{W(CO)5 }2 ] (E=P (1 a), As (1 b); Cp*=C5 Me5 ) with carbodiimides leads to the new four-membered heterocycles of the type [Cp*C(NR)2 E{W(CO)5 }2 ] (E=P: R=iPr (2 a), Cy (3 a); E=As: R=iPr (2 b), Cy (3 b)). The reaction of phosphinidene complex 1 a with alkyl azides yields the triazaphosphete derivatives [Cp*P{W(CO)5 }N(R)NN{W(CO)5 }] (R=Hex, Cy) (4). These unprecedented N3 P four-membered triazaphosphete complexes can be regarded as stabilized intermediates of the Staudinger reaction, which have not been previously isolated. All of the isolated products were characterized by NMR, IR spectroscopy, mass spectrometry, and by single-crystal X-ray diffraction analysis.
Chemistry: A European Journal | 2010
Markus Stubenhofer; Christian Kuntz; Michael Bodensteiner; Ulrich Zenneck; Marek Sierka; Manfred Scheer
Photolysis of [Cp*As{W(CO)(5)}(2)] (1a) in the presence of Mes*P=PMes* (Mes*=2,4,6-tri-tert-butylphenyl) leads to the novel 1,3-diphospha-2-arsaallyl radical [(CO)(5)W(mu,eta(2):eta(1)-P(2)AsMes*(2))W(CO)(4)] (2a). The frontier orbitals of the radical 2a are indicative of a stable pi-allylic system that is only marginally influenced by the d orbitals of the two tungsten atoms. The SOMO and the corresponding spin density distribution of the radical 2a show that the unpaired electron is preferentially located at the two equivalent terminal phosphorus atoms, which has been confirmed by EPR spectroscopy. The protonated derivative of 2a, the complex [(CO)(5)W(mu,eta(2):eta(1)-P(2)As(H)Mes*(2))W(CO)(4)] (6a) is formed during chromatographic workup, whereas the additional products [Mes*P=PMes*{W(CO)(5)}] as the Z-isomer (3) and the E-isomer (4), and [As(2){W(CO)(5)}(3)] (5) are produced as a result of a decomposition reaction of radical 2a. Reduction of radical 2a yields the stable anion [(CO)(5)W(mu,eta(2):eta(1)-P(2)AsMes*(2))W(CO)(4)](-) in 7a, whereas upon oxidation the corresponding cationic complex [(CO)(5)W(mu,eta(2):eta(1)-P(2)AsMes*(2))W(CO)(4)][SbF(6)] (8a) is formed, which is only stable at low temperatures in solution. Compounds 2a, 7a, and 8a represent the hitherto elusive complexed redox congeners of the diphospha-arsa-allyl system. The analogous oxidation of the triphosphaallyl radical [(CO)(5)W(mu,eta(2):eta(1)- P(3)Mes*(2))W(CO)(4)] (2b) also leads to an allyl cation, which decomposes under CH activation to the phosphine derivative [(CO)(5)W{mu,eta(2):eta(1)-P(3)(Mes*)(C(5)H(2)tBu(2)C(CH(3))(2)CH(2))}W(CO)(4)] (9), in which a CH bond of a methyl group of the Mes* substituent has been activated. All new products have been characterized by NMR spectrometry and IR spectroscopy, and compounds 2a, 3, 6a, 7a, and 9 by X-ray diffraction analysis.
Archive | 2013
Markus Stubenhofer; Christian Kuntz; Michael Bodensteiner; Alexey Y. Timoshkin; Manfred Scheer
Related Article: Markus Stubenhofer, Christian Kuntz, Michael Bodensteiner, Alexey Y. Timoshkin, and Manfred Scheer|2013|Organometallics|32|3521|doi:10.1021/om400357y
Angewandte Chemie | 2009
Manfred Scheer; Christian Kuntz; Markus Stubenhofer; Michael Linseis; Rainer F. Winter; Marek Sierka
Angewandte Chemie | 2007
Manfred Scheer; Daniel Himmel; Brian P. Johnson; Christian Kuntz; Michael Schiffer
Angewandte Chemie | 2007
Manfred Scheer; Daniel Himmel; Brian P. Johnson; Christian Kuntz; Michael Schiffer
Angewandte Chemie | 2010
Manfred Scheer; Christian Kuntz; Markus Stubenhofer; Manfred Zabel; Alexey Y. Timoshkin