Average oxidation state

The reduction of molybdate salts in acidic solutions leads to the formation of the molybdenum blues (9). Reductants include dithionite, staimous ion, hydrazine, and ascorbate. The molybdenum blues are mixed-valence compounds where the blue color presumably arises from the intervalence Mo(V) — Mo(VI) electronic transition. These can be viewed as intermediate members of the class of mixed oxy hydroxides the end members of which are Mo(VI)02 and Mo(V)0(OH)2 [27845-91-6]. MoO and Mo(VI) solutions have been used as effective detectors of reductants because formation of the blue color can be monitored spectrophotometrically. The nonprotonic oxides of average oxidation state between V and VI are the molybdenum bronzes, known for their metallic luster and used in the formulation of bronze paints (see Paint). 

It is clear that, if synthetic routes could be devised which would mechanistically hinder disproportionation, such compounds might be preparable. Although univalent compounds of the Group 2 metals have not yet been isolated, there is some evidence for the formation of Mg species during electrolysis with Mg electrodes. Thus H2 is evolved at the anode when an aqueous solution of NaCl is electrolysed and the amount of Mg lost from the anode corresponds to an oxidation state of 1.3. Similarly, when aqueous Na2S04 is electrolysed, the amount of H2 evolved corresponds to the oxidation by water of Mg ions having an average oxidation state of 1.4 ... 

In both cases the average oxidation state of the metal is reduced. It is important to appreciate that. 

Average oxidation state Examples Structural features... 

The original blue (K.A. Hofmann, 1908) was obtained from the reaction of Pt(MeCN)2Cl2 with silver salts over some hours. Under these conditions, the nitrite is hydrolysed to acetamide. Very recently, the structure of the complex [(H3N)2Pt(MeCONH)2Pt(NH3)2]4(NO3)10 has been determined (Figure 3.37). The average oxidation state of the platinums in the octamer is 2.25. 

Gold, unlike silver, forms a wide range of cluster complexes [184] where the average oxidation state of the metal is below +1 they may be synthesized by reduction of gold(I) phosphine complexes ... 

A number of metal oxides are known to form nonstoicbiometric compounds, in which the ratios of atoms that make up the compound cannot be expressed in small whole numbers. In the crystal structure of a nonstoichiometric compound, some of the lattice points where one would have expected to find atoms are vacant. Transition metals most easily form nonstoichiometric compounds because of the number of oxidation states that they can have. For example, a titanium oxide with formula TiO, I( is known, (a) Calculate the average oxidation state of titanium in this compound. 

Uranium dioxide, UQ2, can be further oxidized to give a nonstoichiometric compound U024v, where 0 < x < 0.25. See Exercise 5.77 for a description of nonstoichiometric compounds, (a) What is the average oxidation state of uranium in a compound with composition UO,j-> (b) If we assume that the uranium exists in either the +4 or the +5 oxidation state, what is the fraction of uranium ions in each ... 

Consequently, the activated complex (X ) of the rate-determining step is composed of one Ce atom and one Cr atom, the average oxidation state of each atom being -t-4 [X = 2 Ce(IV)4-Cr(III)—Ce(III)]. A sequence of one-equivalent steps are in accord with the rate law, viz. 

In situ UV-Vis Diffuse Reflectance Spectroscopy was performed under reactive atmosphere ( -butane/oxygen). These experiments confirmed that submitting the catalyst to the reaction mixture favors the development of a more oxidized active surface, and that the extent of transformation depends on the reaction temperature and on the catalyst P/V ratio. For instance, catalyst P/V 1.06 was less oxidized than catalyst P/V 1.00 at a temperature lower than 340°C. X-ray Photoelectron spectra of catalysts recorded after reaction at 380°C confirmed that catalyst P/V 1.00 was considerably more oxidized (average oxidation state for surface V 4.23) than the P/V 1.06 catalyst (average oxidation state 4.03). 

For the purpose of this discussion, a mixed valence compound is defined as a compound containing two or more metal atoms with an average oxidation state which is either... 

It has been reported that the value of the cubic lattice parameter, which is directly related to the average oxidation state of the manganese, is critical to obtain effective cycling. The lattice parameter should preferably be 8.23A or less, and such values are associated with lithium-rich materials, Lii+Mriz-jOi, where the average manganese oxidation state is 3.58 or higher this value minimizes dissolution of manganese and also the impact of the... 

---