Automotive Bankruptcy Panel Discussion - November 16, 2009

This panel discussion concerning bankruptcy and the automobile industry took place in the Joseph W. Bartunek III Moot Court Room on the campus of the Cleveland-Marshall College of Law on November 16, 2009

Synthesis, Characterization, and Reactivity of New Hydride Compounds of Tantalum (V)

A series of (pentamethylcyclopentadienyl)tantalum bis(phosphine) polyhydride complexes, Cp*TaL2H4 (L = PMe3, PMe2(C6H5), P(OMe)3, and L2 dmpe; Cp* = η5 - C5(CH3)5) and Cp*Ta(PMe3)2H3Cl, have been prepared by high pressure hydrogenation of Cp*TaMe4 or Cp*TaMe3Cl in the presence of L. The hydride ligands are more hydridic than protic in character. All of the compounds react with acetone and methanol to afford isopropoxide and methoxide complexes, respectively. Reactions with carbon monoxide yield carbonyl hydride and dicarbonyl compounds resulting from sequential reductive elimination of dihydrogen. Hydrogenation of ethylene is observed, as well as catalytic dimerization of ethylene to 1-butene. Most reactions of these eighteen-electron polyhydride complexes are thought to involve rate-determining loss of a phosphine ligand. Evidence is presented in support of coordination of acetone to tantalum prior to its reduction to isopropoxide. By contrast, methanol can react qirectly with the coordinatively saturatedtantalum hydride species to generate H2. Low temperature and high field NMR spectroscopy has been used to investigate the coordination geometries of these polyhydride complexes and some niobium analogues. Using symmetry arguments, the spectra indicate a Cs structure with equivalent phosphorus atoms for complexes with monodentate phosphine ligands. This is consistent with an X-ray crystal structure of Cp*Ta(PMe3)2H4, in which the hydride ligands were not located. A different Cs structure, with inequivalent phosphorus atoms, is indicated for compounds with the bidentate dmpe ligand. The reactions of Cp*TaMe3Cl (1) with a variety of alkali metal alkoxide, alkylamide, and alkyl reagents have been examined. Reaction with LiNMe2 produces Cp*Ta(NMe2)Me3, but this decomposes at 25°C to an imine (or metallaazirane) complex, Cp*Ta(CH2NMe)Me2. The decomposition is a first-order, unimolecular process with a large kinetic isotope effect kH/kD = 9.7). Monoalkylamides (LiNHR) react with 1 to form imido complexes Cp*Ta(NR)Me2. Reaction of 1 with lithium diisopropylamide forms a bridging methylene complex, Cp*Me2Ta(µCH2)(µH)2TaMe2Cp*. The alkoxide compounds Cp*Ta(OR)Me3 (R = Me, CHMe2, CMe3) are very stable and decompose only over 100°C. Alkyl complexes are stable only if the alkyl group does not have β-hydrogens. The rates of hydrogen abstraction or elimination processes in this system correlate with the nature of the atom bound to tantalum: for reactions involving a β-hydrogen the order is C &gt; N &gt; O while α-hydrogen abstraction reactions appear to vary in the reverse order, N &gt; C. These rates seem to reflect the thermodynamic preferences in these compounds. Hydrogenation of the imido compounds (Cp*Ta(NR)Me2) in the presence of phosphine ligands yield the first examples of imido-hydride complexes, Cp*Ta(NR)H2(L) (L = PMe3, PMe2(C6H5), R = CMe3, CH2CM3). An alkyl-hydride complex, Cp*Ta(CH2NMe)Me(PMe3)H, has also been prepared. The reaction of Cp*TaMe3(OCMe3) with hydrogen forms an unusual asymmetric dimer, Cp*(Me3CO)2HTa(µH)2 TaH3Cp*, which has been characterized by NMR and IR spectroscopies. The tantalum hetero-olefin complexes Cp*Ta(CH2NMe)Me2 and Cp*Ta(OCMe2)Me2 react readily with olefins, aldehydes, and nitriles. A number of five- and seven-atom metallacycles have been prepared.</p

Conditioning nano-LEDs in arrays by laser-micro-annealing: The key to their performance improvement

A local so-called laser-micro-annealing (LMA) conditioning technology, which is suitable for the fabrication of a large range of hybrid nano-optoelectronic devices, was applied to III-nitride-based nano-light emitting diodes (LEDs). The LEDs with a diameter of ∼100 nm were fabricated in large area arrays and designed for hybrid optoelectronic applications. The LMA process was developed for the precise local conditioning of LED nano-structures. Photoluminescence measurements reveal the enhancement of nano-LED properties, which is in very good agreement with a simple model introduced based on the reduction of the defect layer depth by the LMA process. The experimental data confirm the reduction of the defect layer depth from ∼17 nm to ∼5 nm determined. In consequence, an increase in work currents up to 40 nA at 5 V bias after the LMA procedure as well as high electroluminescence (EL) and output optical power up to 150 nW in the ∼440–445 nm emission wavelength range corresponding to ∼75% wall-plug efficiency were achieved. Additionally, the LEDs' electroluminescence intensities reach the desired values by conditioning the contact/annealed regions of individual LEDs accordingly. Furthermore, the LMA process affects the long-term stability of the electroluminescence (EL) intensity of single nano-LED devices. A study of the EL during 5000 h in the continuous wave operation testing mode revealed a moderate ∼15% decrease in the intensity in comparison to ∼50% for their non-LMA counterparts. Finally, Raman measurements indicate that the “work” temperature for nano-LED conditioned structures decreases