The prediction of metal-to-metal bonding in transition metal binary and related compounds

1964 ◽  
Vol 17 (11) ◽  
pp. 1191 ◽  
Author(s):  
JC Sheldon
Keyword(s):  
Transition Metal ◽  
Metal Oxides ◽  
Transition Metal Oxides ◽  
Valence State ◽  
Oxidation States ◽  
Metal Bonding ◽  
Binary Oxides ◽  
Lower Oxidation ◽  
D Orbitals ◽  
Related Compounds

The evidence for, and the factors determining, the formation of metal-to-metal (m-m) bonds in transition metal oxides, sulphides, halides, and related complexes are discussed. It is proposed that when metals of high preferred valence state are constrained to low formal oxidation states, m-m bonds will form to allow the metal to exercise a higher valency. It is assumed that (n-l)d orbitals are used for such bonds and predictions of the feasibility of m-m bonding are possible by the comparison of the size of such orbitals with the expected inter-metal distances in polymeric metal oxides and halides. It is concluded that binary oxides and halides (excepting fluorides) of the lower oxidation states of Zr, Hf, Nb, Ta, Mo, W, and Re and of a few neighbouring elements will display m-m bonds.

scholarly journals Nanostructured transition metal oxides obtained by SPVD

2020 ◽  
Vol 7 ◽  
pp. 12
Author(s):  
Adriana Gabriela Plăiașu ◽  
Marian Cătălin Ducu ◽  
Sorin Georgian Moga ◽  
Aurelian Denis Negrea ◽  
Ecaterina Magdalena Modan
Keyword(s):  
Transition Metal ◽  
Metal Oxides ◽  
Transition Metal Oxides ◽  
Physical Vapor Deposition ◽  
Manganese Oxides ◽  
Oxidation States ◽  
Microstructural Characteristics ◽  
Original Process ◽  
Synthesis Parameters ◽  
D Orbitals

The interest in the unique properties associated with materials having structures on a nanometer scale has been increasing at an exponential rate in last decade. Transition metal oxides are preferred materials for catalytic applications due to their half-filled d orbitals that make them exist in different oxidation states. Transition metal oxides show a broad structural variety due to their ability to form phases of varying metal to oxygen ratios reflecting multiple stable oxidation states of the metal ions. The Solar Physical Vapor Deposition (SPVD) presented in the paper as elaboration method is an original process to prepare nanopowders working under concentrated sunlight in 2 kW solar furnaces. The influence of the synthesis parameters on the chemical and microstructural characteristics of zinc and manganese oxides synthesized nanophases has been systematically studied using XRD, SEM and EDX.

Organo-transition metal oxides and sulphides: A tetranuclear η-cyclopentadienylmolybdenum oxide and related compounds

1977 ◽  
Vol 131 (3) ◽  
pp. C40-C42 ◽  
Author(s):  
Jean-Claude Daran ◽  
Keith Prout ◽  
George J.S. Adam ◽  
Malcolm L.H. Green ◽  
Jean Sala-Pala
Keyword(s):  
Transition Metal ◽  
Metal Oxides ◽  
Transition Metal Oxides ◽  
Related Compounds

X-ray Absorption Spectroscopic Study on Valence State and Local Atomic Structure of Transition Metal Oxides Doped in MgH2

2009 ◽  
Vol 113 (30) ◽  
pp. 13450-13455 ◽  
Author(s):  
Nobuko Hanada ◽  
Takayuki Ichikawa ◽  
Shigehito Isobe ◽  
Tessui Nakagawa ◽  
Kazuhiko Tokoyoda ◽  
...  
Keyword(s):  
Transition Metal ◽  
Metal Oxides ◽  
Spectroscopic Study ◽  
Atomic Structure ◽  
Transition Metal Oxides ◽  
Valence State ◽  
Local Atomic Structure ◽  
X Ray ◽  
State And Local ◽  
X Ray Absorption

A New Route for The Synthesis of Reduced Transition Metal Oxides Using Borohydrides

1994 ◽  
Vol 346 ◽  
Author(s):  
A. Manthiram ◽  
Y. T. Zhu ◽  
A. Dananjay
Keyword(s):  
Low Temperature ◽  
Transition Metal ◽  
Alkali Metal ◽  
Metal Oxides ◽  
Transition Metal Oxides ◽  
X Ray Diffraction ◽  
Reaction Conditions ◽  
X Ray ◽  
Binary Oxides ◽  
Oxide Bronzes

ABSTRACTReduction of aqueous solutions of tungstates, molybdates or vanadates by aqueous alkali metal borohydrides at ambient‐temperature results in a formation of dark colored gel. The gel is amorphous to X‐ray diffraction and crystallizes sharply at around 300‐500 °C to yield reduced transition metal oxides such as the oxide bronzes, NaxMyOz, or the binary oxides, MO2 (M = V, Mo or W). The nature and composition of the products formed are strongly influenced by the reaction conditions such as the reaction pH as well as the concentration and amount of the reagents. Experimental procedures to obtain the different phases are presented. This novel low‐temperature approach has a potential to access new metastable phases.

HREM Study of electron-induced surface radiation damage in ReO3

1991 ◽  
Vol 49 ◽  
pp. 636-637
Author(s):  
R. Ai ◽  
H.-J. Fan ◽  
L. D. Marks
Keyword(s):  
Transition Metal ◽  
Metal Ions ◽  
Metal Oxides ◽  
Electron Irradiation ◽  
Transition Metal Oxides ◽  
Carbon Film ◽  
Transition Metal Ions ◽  
Surface Radiation ◽  
Valence Transition ◽  
Electron Microscopes

It has been known for a long time that electron irradiation induces damage in maximal valence transition metal oxides such as TiO2, V2O5, and WO3, of which transition metal ions have an empty d-shell. This type of damage is excited by electronic transition and can be explained by the Knoteck-Feibelman mechanism (K-F mechanism). Although the K-F mechanism predicts that no damage should occur in transition metal oxides of which the transition metal ions have a partially filled d-shell, namely submaximal valence transition metal oxides, our recent study on ReO3 shows that submaximal valence transition metal oxides undergo damage during electron irradiation.ReO3 has a nearly cubic structure and contains a single unit in its cell: a = 3.73 Å, and α = 89°34'. TEM specimens were prepared by depositing dry powders onto a holey carbon film supported on a copper grid. Specimens were examined in Hitachi H-9000 and UHV H-9000 electron microscopes both operated at 300 keV accelerating voltage. The electron beam flux was maintained at about 10 A/cm2 during the observation.

Problems with oxygen analysis in the system MgO-Al2O3-SiO2 with the electron microprobe

1992 ◽  
Vol 50 (2) ◽  
pp. 1624-1625
Author(s):  
Michel Fialin ◽  
Guy Rémond
Keyword(s):  
Transition Metal ◽  
Metal Oxides ◽  
Transition Metal Oxides ◽  
Electrostatic Charge ◽  
Carbon Layer ◽  
Sample Holder ◽  
Rock Matrix ◽  
Electrical Discharges ◽  
Thin Carbon ◽  
Beam Instabilities

Oxygen-bearing minerals are generally strong insulators (e.g. silicates), or if not (e.g. transition metal oxides), they are included within a rock matrix which electrically isolates them from the sample holder contacts. In this respect, a thin carbon layer (150 Å in our laboratory) is evaporated on the sections in order to restore the conductivity. For silicates, overestimated oxygen concentrations are usually noted when transition metal oxides are used as standards. These trends corroborate the results of Bastin and Heijligers on MgO, Al2O3 and SiO2. According to our experiments, these errors are independent of the accelerating voltage used (fig.l).Owing to the low density of preexisting defects within the Al2O3 single-crystal, no significant charge buildup occurs under irradiation at low accelerating voltage (< 10keV). As a consequence, neither beam instabilities, due to electrical discharges within the excited volume, nor losses of energy for beam electrons before striking the sample, due to the presence of the electrostatic charge-induced potential, are noted : measurements from both coated and uncoated samples give comparable results which demonstrates that the carbon coating is not the cause of the observed errors.

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