Synthesis and stereochemical analysis of the triangular cobalt-dinickel clusters, (.eta.5-C5H5-nMen)CoNi2(.eta.5-C5H5)2(.mu.3-CO)2 (where n = 0, 1, 5): direct evidence for the antibonding trimetal character of the unpaired electron in the Fischer-Palm Ni3(.eta.5-C5H5)3(.mu.3-CO)2 and resulting geometrical effects upon formal oxidation by replacement of a nickel with a cobalt atom

1981 ◽  
Vol 103 (8) ◽  
pp. 1942-1951 ◽  
Author(s):  
Lance R. Byers ◽  
Vernon A. Uchtman ◽  
Lawrence F. Dahl
Keyword(s):  
Unpaired Electron ◽  
Direct Evidence ◽  
Cobalt Atom ◽  
Stereochemical Analysis ◽  
Geometrical Effects

Diolefinbis(trimethyIphosphine)cobalt(0) Compounds: Stable Organometallic Radicals with Distorted Ground State Structures

1988 ◽  
Vol 43 (11) ◽  
pp. 1427-1438 ◽  
Author(s):  
Hans-Friedrich Klein ◽  
Michael Helwig ◽  
Udo Koch ◽  
Goetz Lull ◽  
Marko Tadic ◽  
...  
Keyword(s):  
Unpaired Electron ◽  
Ground State ◽  
Cobalt Atom ◽  
Model System ◽  
Molecular Orbital Calculations ◽  
Electron Model ◽  
Ambient Temperatures ◽  
Bond Lengths ◽  
Allyl Ethers ◽  
Ground State Structures

Abstract Diolefincobalt(O) complexes Co(L2)(PMe3)2 {L2 -[CH2 = CHSi(OMe)2]2O (1), [CH2 =CHSi(OEt)2]2O (2), (CH2 =CHCH2)2SiMe2 (3), [(CH2 =CHCH2)2N]2CH2 (4)} have been synthesized from Co(C5H8)(PMe3)3 and diolefins at ambient temperatures. Reactions with allyl ethers or with allyltin or allylphosphorus compounds involve transfer of allyl groups to the cobalt, while allylamine simply replaces cyclopentene (C5H8) to give Co(CH2 =CHCH2NH2)(PMe3)3 (5). Cationic cobalt(I) complexes containing olefin ligands as in 1-4 could not be obtained under conditions where norbornadiene readily gave [Co(C7H8)(PMe3)3 ]BF4 (6). Paramagnetic 4 shows a magnetic moment μeff = 2.0 μв (between 3.6 and 293 K), corresponding to one unpaired electron per cobalt atom. Compound 4 crystallizes in the space group P21/c with Z = 4, a = 14.986(4), b = 17.223(5), c = 15.436(3) Å,β = 117.98(2)°, V = 3518.4 Å3 . Each cobalt atom is η4-coordinated to a diolefin involving the smaller of two possible chelating rings. The Co-C distances range only from 2.029(6) to 2.058(6) Å for the olefin ligands, whereas Co-P bond lengths at each cobalt differ significantly: Co1-P1 2.188(2), Co1-P2 2.248(2); Co2-P3 2.185(2), Co2-P4 2.258(2) Å. This feature of two significantly different Co-L bond lengths is hitherto seen in all structurally characterized (bisolefin)CoL2 complexes (L = PMe3, CH3CN) and can be rationalized by molecular orbital calculations (Extended Hückel) on the 17 electron model system (PH3)2Co(C2H4)2.

The Immuno-Electron Microscopic Localization of the Mo-Fe Protein Component of Nitrogenase in Cells of Azotobacter Vinelandii

1973 ◽  
Vol 31 ◽  
pp. 574-575
Author(s):  
J. T. Stasny ◽  
R. C. Burns ◽  
R. W. F. Hardy
Keyword(s):  
Cellular Localization ◽  
Direct Evidence ◽  
Azotobacter Vinelandii ◽  
Intracellular Localization ◽  
Protein Component ◽  
Electron Microscopic ◽  
Thin Sections ◽  
Fe Protein ◽  
Intracytoplasmic Membranes

Structure-functlon studies of biological N2-fixation have correlated the presence of the enzyme nitrogenase with increased numbers of intracytoplasmic membranes in Azotobacter. However no direct evidence has been provided for the internal cellular localization of any nitrogenase. Recent advances concerned with the crystallizatiorTand the electron microscopic characterization of the Mo-Fe protein component of Azotobacter nitrogenase, prompted the use of this purified protein to obtain antibodies (Ab) to be conjugated to electron dense markers for the intracellular localization of the protein by electron microscopy. The present study describes the use of ferritin conjugated to goat antitMo-Fe protein immunoglobulin (IgG) and the observations following its topical application to thin sections of N2-grown Azotobacter.

Structural similarity of ribosomes from E. coli and A. salina

1978 ◽  
Vol 36 (2) ◽  
pp. 242-243
Author(s):  
M. Boublik ◽  
R.M. Wydro ◽  
W. Hellmann ◽  
F. Jenkins
Keyword(s):  
Ribosomal Proteins ◽  
Direct Evidence ◽  
Structural Similarity ◽  
Carbon Support ◽  
Artemia Salina ◽  
Uranyl Acetate ◽  
Biological Assays ◽  
E Coli ◽  
And Function ◽  
Fine Carbon

Ribosomes are ribonucleoprotein particles necessary for processing the genetic information of mRNA into proteins. Analogy in composition and function of ribosomes from diverse species, established by biochemical and biological assays, implies their structural similarity. Direct evidence obtained by electron microscopy seems to be of increasing relevance in understanding the structure of ribosomes and the mechanism of their role in protein synthesis.The extent of the structural homology between prokaryotic and eukaryotic ribosomes has been studied on ribosomes of Escherichia coli (E.c.) and Artemia salina (A.s.). Despite the established differences in size and in the amount and proportion of ribosomal proteins and RNAs both types of ribosomes show an overall similarity. The monosomes (stained with 0.5% aqueous uranyl acetate and deposited on a fine carbon support) appear in the electron micrographs as round particles with a diameter of approximately 225Å for the 70S E.c. (Fig. 1) and 260Å for the 80S A.s. monosome (Fig. 2).

Stress Relaxation and the Formation of Silicides in the Process of the Crystallization of NI-NB Films on SI

1991 ◽  
Vol 49 ◽  
pp. 898-899
Author(s):  
N. Rozhanski ◽  
V. Lifshitz
Keyword(s):  
Thin Films ◽  
Stress Relaxation ◽  
Integrated Circuits ◽  
Direct Evidence ◽  
Alloy Film ◽  
Diffusion Barriers ◽  
Effective Barrier

Thin films of amorphous Ni-Nb alloys are of interest since they can be used as diffusion barriers for integrated circuits on Si. A native SiO2 layer is an effective barrier for Ni diffusion but it deformation during the crystallization of the alloy film lead to the appearence of diffusion fluxes through it and the following formation of silicides. This study concerns the direct evidence of the action of stresses in the process of the crystallization of Ni-Nb films on Si and the structure of forming NiSi2 islands.

Point and planar defects in the iron sulfide compounds Fe1-xS

1984 ◽  
Vol 42 ◽  
pp. 434-435
Author(s):  
Thao A. Nguyen
Keyword(s):  
Low Temperatures ◽  
Direct Evidence ◽  
Iron Sulfide ◽  
Planar Defects ◽  
Selective Area ◽  
Vacancy Ordering ◽  
Different Types ◽  
Lattice Images ◽  
The Subject ◽  
Beam Lattice

It is well known that the large deviations from stoichiometry in iron sulfide compounds, Fe1-xS (0≤x≤0.125), are accommodated by iron vacancies which order and form superstructures at low temperatures. Although the ordering of the iron vacancies has been well established, the modes of vacancy ordering, hence superstructures, as a function of composition and temperature are still the subject of much controversy. This investigation gives direct evidence from many-beam lattice images of Fe1-xS that the 4C superstructure transforms into the 3C superstructure (Fig. 1) rather than the MC phase as previously suggested. Also observed are an intrinsic stacking fault in the sulfur sublattice and two different types of vacancy-ordering antiphase boundaries. Evidence from selective area optical diffractograms suggests that these planar defects complicate the diffraction pattern greatly.

Evidence for ordered Fe3Ni

1987 ◽  
Vol 45 ◽  
pp. 216-217
Author(s):  
K.B. Reuter ◽  
D.B. Williams ◽  
J.I. Goldstein
Keyword(s):  
Experimental Data ◽  
Martensitic Transformation ◽  
Electron Diffraction ◽  
Room Temperature ◽  
Direct Evidence ◽  
Transformation Product ◽  
Iron Meteorites ◽  
X Ray ◽  
Ni Content ◽  
Temperature Transformation

In the Fe-Ni system, although ordered FeNi and ordered Ni3Fe are experimentally well established, direct evidence for ordered Fe3Ni is unconvincing. Little experimental data for Fe3Ni exists because diffusion is sluggish at temperatures below 400°C and because alloys containing less than 29 wt% Ni undergo a martensitic transformation at room temperature. Fe-Ni phases in iron meteorites were examined in this study because iron meteorites have cooled at slow rates of about 10°C/106 years, allowing phase transformations below 400°C to occur. One low temperature transformation product, called clear taenite 2 (CT2), was of particular interest because it contains less than 30 wtZ Ni and is not martensitic. Because CT2 is only a few microns in size, the structure and Ni content were determined through electron diffraction and x-ray microanalysis. A Philips EM400T operated at 120 kV, equipped with a Tracor Northern 2000 multichannel analyzer, was used.

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