The reactivity of the high-energy intermediates formed in the reactions of Group 13 metal atoms and aromatic alkenes

1998 ◽  
Vol 76 (4) ◽  
pp. 400-406 ◽  
Author(s):  
Helen A Joly ◽  
Maria Kepes ◽  
Natalie Roy ◽  
Jason Prpic
Keyword(s):  
Metal Atom ◽  
High Energy ◽  
Spectroscopic Studies ◽  
Reductive Coupling ◽  
Group 13 ◽  
Metal Atoms ◽  
Metal Atom Reactions ◽  
Cis And Trans ◽  
Rotating Cryostat

Group 13 metal atoms were reacted with aromatic alkenes in a specialized metal atom reactor known as a "rotating cryostat." The nature of the intermediates formed was deduced from a GC-MS study of their hydrolysis and deuterolysis products. The product studies suggest that 2-phenylaluminacyclopropane, cis- and trans-3,4-diphenylaluminacyclopentane, and cis- and trans- 2,4-diphenylaluminacyclopentane are formed when Al atoms react with styrene, and 2-methyl-2-phenylaluminacyclopropane and 3,4-dimethyl- 3,4-diphenylaluminacyclopentane are formed when Al atoms react with α -methylstyrene. These findings are consistent with the radicals detected in the EPR spectroscopic studies of Al-alkene reaction mixtures prepared under similar conditions. Mechanisms for the formation of the organoaluminium intermediates are discussed. Analogous organogallium intermediates are formed when gallium atoms react with styrene. The reductive coupling of styrene did not occur when In and Tl atoms were used. Only trace quantities of phenylethane were detected in the hydrolyzed reaction mixture.Key words: Group 13 metal atoms, aluminium atoms, organoaluminium intermediates, metal atom reactions.

Metal Atom Reactions with Polymer Films

1986 ◽  
Vol 72 ◽  
Author(s):  
Caroline A. Kovac ◽  
Jean L. Jordan ◽  
Roger A. Pollak
Keyword(s):  
Synchrotron Radiation ◽  
Metal Atom ◽  
Chemical Nature ◽  
Photoemission Spectroscopy ◽  
Carbonyl Groups ◽  
Complex Chemical ◽  
X Ray ◽  
Metal Atoms ◽  
Metal Atom Reactions ◽  
X Ray Absorption

AbstractThe chemical nature of the interface formed when an electropositive metal (chromium) is evaporated on the surface of oxygen-containing polymers has been investigated by synchrotron-radiation excited photoemission spectroscopy and by near-edge X-ray absorption fine stnrcture spectroscopy (NEXAFS). PMDA-ODA polyimide was studied along with two polymers intended to more simply model the complex chemical functionality of polyimide. Core-level spectra were resolved into distinct peaks, which were assigned to specific atoms in the polymer units, and changes in the spectra were monitored as chromium metal atoms were evaporated onto the surface. Similarly, NEXAFS spectra were taken as a function of chromium deposition. Results of these experiments show that chromium initially reacts very rapidly with surface carbonyl groups, but less strongly with ether oxygens or arene rings. In all polymers studied, formation of an electron-rich, carbide-like species was observed.

Ultra high resolution SEM at high voltage images individual fab fragments applied as molecular label to cell surface receptors

1989 ◽  
Vol 47 ◽  
pp. 70-71
Author(s):  
Klaus-Ruediger Peters
Keyword(s):  
High Resolution ◽  
High Energy ◽  
Metal Coating ◽  
Beam Diameter ◽  
Surface Receptors ◽  
Surface Mobility ◽  
Metal Atoms ◽  
Shadowing Effect ◽  
Imaging Mode ◽  
Deposition Techniques

Topographic ultra high resolution can now routinely be established on bulk samples in cold field emission scanning electron microscopy with a second generation of microscopes (FSEM) designed to provide 0.5 nm probe diameters. If such small probes are used for high magnification imaging, topographic contrast is so high that remarkably fine details can be imaged on 2DMSO/osmium-impregnated specimens at ribosome surfaces even without a metal coating. On TCH/osmium-impregnated specimens topographic resolution can be increased further if the SE-I imaging mode is applied. This requires that beam diameter and metal coating thickness be made smaller than the SE range of ~1 nm and background signal contributions be reduced. Subnanometer small probes can be obtained (only) at high accelerating voltages. Subnanometer thin continuous metal films can be produced under the following conditions: self-shadowing effect between metal atoms must be reduced through appropriate deposition techniques and surface mobility of metal atoms must be diminished through high energy sputtering and/or specimen cooling.

Molecular orbital and spectroscopic studies of triple bonds between transition-metal atoms. 2. The d5-d5 Re2Cl4(PR3)4 compounds

1983 ◽  
Vol 105 (9) ◽  
pp. 2606-2611 ◽  
Author(s):  
Bruce E. Bursten ◽  
F. Albert Cotton ◽  
Phillip E. Fanwick ◽  
George G. Stanley ◽  
Richard A. Walton
Keyword(s):  
Transition Metal ◽  
Molecular Orbital ◽  
Spectroscopic Studies ◽  
Triple Bonds ◽  
Metal Atoms ◽  
Transition Metal Atoms

Low-Temperature Diffusion of Transition Metals at the Presence of Radiation Defects in Silicon

2011 ◽  
Vol 178-179 ◽  
pp. 421-426
Author(s):  
Jan Vobecký ◽  
Volodymyr Komarnitskyy ◽  
Vít Záhlava ◽  
Pavel Hazdra
Keyword(s):  
Low Temperature ◽  
Active Sites ◽  
Carrier Lifetime ◽  
High Energy ◽  
Deep Levels ◽  
Radiation Defects ◽  
Metal Atoms ◽  
Temperature Diffusion ◽  
Concentration Enhancement ◽  
Application Potential

Low-temperature diffusion of Cr, Mo, Ni, Pd, Pt, and V in silicon diodes is compared in the range 450 - 800 oC. Before the diffusion, the diodes were implanted with high-energy He2+ to assess, if the radiation defects enhance the concentration of metal atoms at electrically active sites and what is the application potential for carrier lifetime control. The devices were characterized using AES, XPS, DLTS, OCVD carrier lifetime and diode electrical parameters. The metal atoms are divided into two groups. The Pt, Pd and V form deep levels in increased extent at the presence of radiation defects above 600 oC, which reduces the excess carrier lifetime. It is shown as a special case that the co-diffusion of Ni and V from a NiV surface layer results fully in the concentration enhancement of the V atoms. The enhancement of the acceptor level V-/0 (EC 0.203 eV) and donor level V0/+ (EC 0.442 eV) resembles the behavior of substitutional Pts. The second group is represented by the Mo and Cr. They easily form oxides, which can make their diffusion into a bulk more difficult or impossible. Only a slight enhancement of the Cr-related deep levels by the radiation defects has been found above 700 oC.

Hexaruthenium and octaruthenium carbonyl cluster complexes derived from 2-amino-6-methylpyridine — Novel coordination modes for 2-imidopyridines

2006 ◽  
Vol 84 (2) ◽  
pp. 105-110 ◽  
Author(s):  
Javier A Cabeza ◽  
Ignacio del Río ◽  
Pablo García-Álvarez ◽  
Daniel Miguel
Keyword(s):  
Metal Atom ◽  
Cluster Compounds ◽  
Carbonyl Cluster ◽  
Amido Ligands ◽  
Ruthenium Cluster ◽  
Coordination Type ◽  
Metal Atoms ◽  
Pyridine Nitrogen ◽  
Cluster 2 ◽  
Reflux Temperature

The hexanuclear ruthenium cluster [Ru6(µ3-H)2(µ-H)2(µ4-κ2-ampy)2(CO)14] (1) and the octanuclear one [Ru8(µ-H)(µ4-κ2-ampy)3(µ3-κ2-Hampy)(µ-CO)2(CO)15] (2) have been prepared by treating [Ru6(µ3-H)2(µ5-κ2-ampy)(µ-CO)2(CO)14] with 2-amino-6-methylpyridine (H2ampy) in decane at reflux temperature. Their metal atoms are supported by ligands that derive from the activation of one (complex 2) or both N—H bonds (complexes 1 and 2) of the H2ampy amino fragment. Both contain at least one ampy ligand featuring an unprecedented coordination type: the imido N atom caps a triangle of metal atoms while the pyridine nitrogen is attached to an additional metal atom. One of the ampy ligands of cluster 2 also displays another unprecedented coordination type: it caps a distorted square of metal atoms through the imido N atom while the pyridine nitrogen is attached to one of the atoms included in that square.Key words: ruthenium, cluster compounds, amido ligands, imido ligands.

Metal atom reactions with fluorocarbons. 9. Preparation and spectral analyses of (perfluoroalkyl)- and (perfluoroaryl)palladium halides

1980 ◽  
Vol 19 (12) ◽  
pp. 3719-3724 ◽  
Author(s):  
Kenneth J. Klabunde ◽  
Bruce B. Anderson ◽  
Kent Neuenschwander
Keyword(s):  
Metal Atom ◽  
Spectral Analyses ◽  
Metal Atom Reactions

Interactions gauches et chemins réactionnels. Etudes conformationnelles d'hydroxyalkyl-4 cyclohexènes contraints

1981 ◽  
Vol 59 (5) ◽  
pp. 859-864
Author(s):  
Jeanine Bouteiller-Prati ◽  
Jean-Claude Bouteiller ◽  
Jean-Pierre Aycard
Keyword(s):  
Free Energy ◽  
Reaction Path ◽  
High Energy ◽  
Nmr Study ◽  
Conformational Equilibria ◽  
The Stability ◽  
Cis And Trans ◽  
Conformational Free Energy

From J and δ values determined by the nmr study of alcohols obtained by addition of CH3Li and LiAlH4 to the exocyclic carbonyl of cis and trans 3-alkyl 4-carbomethoxy (or acetyl) cyclohexenes (alkyl = H, CH3, C(CH3)3), we have deduced the conformational free energy values (ΔG0X) of the CH(CH3)OH and C(CH3)2OH substituents (0.62 and 2.08 kcal mol−1 respectively) as well as the values for some related conformational equilibria. For transtert-butyl derivatives the stability of the diaxial conformer agrees with a reaction path involving high energy conformers.

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