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Lower oxidation states oxides

As a result of these multiple redox reactions, while hexavalent Cr(VI) is reduced to its lower oxidation state oxides and hydroxides, the substrate metal is oxidized to its oxides and hydroxides. The pH also rises to the point where triva-lent chromium and other oxide/hydroxide compounds are insoluble. " Consequently, a protective conversion coating of adherent composite oxide/hydroxides form with the general formula of MPg/CrP, and/or M(OH),/Cr(OH) where M = Fe, Al.2 ... [Pg.56]

Pb + 40H + 2H2O [PbfOH) ] + H2t Notice, again, that the lower oxidation state of lead is formed. [Pg.171]

When the characteristic element is partially or wholly present in a lower oxidation state than corresponds to its Periodic Group number, oxidation numbers are used for example, [O2HP—O—P03H] , dihydrogendiphosphate(III,V)(2—). [Pg.219]

Oxides of nitrogen, NO, can also form. These are generally at low levels and too low an oxidation state to consider water scmbbing. A basic reagent picks up the NO2, but not the lower oxidation states the principal oxide is usually NO, not NO2. Generally, control of NO is achieved by control of the combustion process to minimize NO, ie, avoidance of high temperatures in combination with high oxidant concentrations, and if abatement is required, various approaches specific to NO have been employed. Examples are NH injection and catalytic abatement (43). [Pg.58]

Many mercury compounds are labile and easily decomposed by light, heat, and reducing agents. In the presence of organic compounds of weak reducing activity, such as amines (qv), aldehydes (qv), and ketones (qv), compounds of lower oxidation state and mercury metal are often formed. Only a few mercury compounds, eg, mercuric bromide/77< 5 7-/7, mercurous chloride, mercuric s A ide[1344-48-5] and mercurous iodide [15385-57-6] are volatile and capable of purification by sublimation. This innate lack of stabiUty in mercury compounds makes the recovery of mercury from various wastes that accumulate with the production of compounds of economic and commercial importance relatively easy (see Recycling). [Pg.112]

The most common oxidation state of niobium is +5, although many anhydrous compounds have been made with lower oxidation states, notably +4 and +3, and Nb can be reduced in aqueous solution to Nb by zinc. The aqueous chemistry primarily involves halo- and organic acid anionic complexes. Virtually no cationic chemistry exists because of the irreversible hydrolysis of the cation in dilute solutions. Metal—metal bonding is common. Extensive polymeric anions form. Niobium resembles tantalum and titanium in its chemistry, and separation from these elements is difficult. In the soHd state, niobium has the same atomic radius as tantalum and essentially the same ionic radius as well, ie, Nb Ta = 68 pm. This is the same size as Ti ... [Pg.20]

All phosphoms oxides are obtained by direct oxidation of phosphoms, but only phosphoms(V) oxide is produced commercially. This is in part because of the stabiUty of phosphoms pentoxide and the tendency for the intermediate oxidation states to undergo disproportionation to mixtures. Besides the oxides mentioned above, other lower oxides of phosphoms can be formed but which are poorly understood. These are commonly termed lower oxides of phosphoms (LOOPs) and are mixtures of usually water-insoluble, yeUow-to-orange, and poorly characteri2ed polymers (58). LOOPs are often formed as a disproportionation by-product in a number of reactions, eg, in combustion of phosphoms with an inadequate air supply, in hydrolysis of a phosphoms trihahde with less than a stoichiometric amount of water, and in various reactions of phosphoms haUdes or phosphonic acid. LOOPs appear to have a backbone of phosphoms atoms having —OH, =0, and —H pendent groups and is often represented by an approximate formula, (P OH). LOOPs may either hydroly2e slowly, be pyrophoric, or pyroly2e rapidly and yield diphosphine-contaminated phosphine. LOOP can also decompose explosively in the presence of moisture and air near 150° C. [Pg.371]

Impurities that form volatile chlorides leave as gases at the top of the furnace together with the TiCl. By cooling those gases, most impurities, with the exception of vanadium and siUcon chlorides can be separated from the titanium tetrachloride [7550-45-0]. Vanadium chlorides can be reduced to lower oxidation state chlorides that are soHds highly volatile SiCl can be removed from TiCl by fractional distillation. [Pg.9]

Organometallic Compounds. Ruthenium, predominately in the oxidation states 0 and +2, forms numerous mononuclear and polynuclear organometaUic compounds. A few examples of compounds in both higher and lower oxidation states also exist. The chemistry of polynuclear mthenium complexes is extensive and has been reviewed (53—59). [Pg.177]

Organometallic Compounds. Osmium forms numerous mononuclear and polynuclear organometaUic complexes, primarily iu lower oxidation states. There are many complexes of carbon monoxide, such as [Os(CO)3] [16406-49-8], [Os(CO) H2] [22372-70-9], [Os3(CO)2 H2] [56398-24-4],... [Pg.179]

The action of redox metal promoters with MEKP appears to be highly specific. Cobalt salts appear to be a unique component of commercial redox systems, although vanadium appears to provide similar activity with MEKP. Cobalt activity can be supplemented by potassium and 2inc naphthenates in systems requiring low cured resin color lithium and lead naphthenates also act in a similar role. Quaternary ammonium salts (14) and tertiary amines accelerate the reaction rate of redox catalyst systems. The tertiary amines form beneficial complexes with the cobalt promoters, faciUtating the transition to the lower oxidation state. Copper naphthenate exerts a unique influence over cure rate in redox systems and is used widely to delay cure and reduce exotherm development during the cross-linking reaction. [Pg.319]

Rhenium Halides and Halide Complexes. Rhenium reacts with chlorine at ca 600°C to produce rheniumpentachloride [39368-69-9], Re2Cl2Q, a volatile species that is dimeric via bridging hahde groups. Rhenium reacts with elemental bromine in a similar fashion, but the metal is unreactive toward iodine. The compounds ReCl, ReBr [36753-03-4], and Rel [59301-47-2] can be prepared by careful evaporation of a solution of HReO and HX. Substantiation in a modem laboratory would be desirable. Lower oxidation state hahdes (Re X ) are also prepared from the pentavalent or tetravalent compounds by thermal decomposition or chemical reduction. [Pg.164]

Some metal thiosulfates are inherently unstable because of the reducing properties of the thiosulfate ion. Ions such as Fe " and Cu " tend to be reduced to lower oxidation states, whereas mercury or silver, which form sulfides of low solubiUty, tend to decompose to the sulfides. The stabiUty of other metal thiosulfates improves in the presence of excess thiosulfate by virtue of complex thiosulfate formation. [Pg.32]

Vanadium, a typical transition element, displays weU-cliaractetized valence states of 2—5 in solid compounds and in solutions. Valence states of —1 and 0 may occur in solid compounds, eg, the carbonyl and certain complexes. In oxidation state 5, vanadium is diamagnetic and forms colorless, pale yeUow, or red compounds. In lower oxidation states, the presence of one or more 3d electrons, usually unpaired, results in paramagnetic and colored compounds. All compounds of vanadium having unpaired electrons are colored, but because the absorption spectra may be complex, a specific color does not necessarily correspond to a particular oxidation state. As an illustration, vanadium(IV) oxy salts are generally blue, whereas vanadium(IV) chloride is deep red. Differences over the valence range of 2—5 are shown in Table 2. The stmcture of vanadium compounds has been discussed (6,7). [Pg.390]

Metal-Catalyzed Oxidation. Trace quantities of transition metal ions catalyze the decomposition of hydroperoxides to radical species and greatiy accelerate the rate of oxidation. Most effective are those metal ions that undergo one-electron transfer reactions, eg, copper, iron, cobalt, and manganese ions (9). The metal catalyst is an active hydroperoxide decomposer in both its higher and its lower oxidation states. In the overall reaction, two molecules of hydroperoxide decompose to peroxy and alkoxy radicals (eq. 5). [Pg.223]

Under polymerisation conditions, the active center of the transition-metal haHde is reduced to a lower valence state, ultimately to which is unable to polymerise monomers other than ethylene. The ratio /V +, in particular, under reactor conditions is the determining factor for catalyst activity to produce EPM and EPDM species. This ratio /V + can be upgraded by adding to the reaction mixture a promoter, which causes oxidation of to Examples of promoters in the eadier Hterature were carbon tetrachloride, hexachlorocyclopentadiene, trichloroacetic ester, and hensotrichloride (8). Later, butyl perchlorocrotonate and other proprietary compounds were introduced (9,10). [Pg.503]

Special containers have been developed for anesthetic ether to prevent deterioration before use. Their effectiveness as stabHizers usuaHy depends on the presence of a lower oxide of a metal having more than one oxidation state. Thus the sides and the bottoms of tin-plate containers are electroplated with copper, which contains a smaH amount of cuprous oxide. Staimous oxide is also used in the linings for tin containers. Instead of using special containers, iron wire or certain other metals and aHoys or organic compounds have been added to ether to stabHize it. [Pg.427]

Oxidations of nitrogen compounds include oxidauon ai nitrogen, when it is in a lower oxidation state, or at a carbon atom in the nitrogen compound. [Pg.347]

Cu ( j -C5H5)2] is not. Likewise, Fe and Ni carborane derivatives are extremely stable. Conversely, metallocarboranes tend to stabilize lower oxidation states of early transition elements and complexes are well established for Ti", Zr , Hf , V , Cr and Mn" these do not react with H2, N2, CO or PPh3 as do cyclopentadienyl derivatives of these elements. [Pg.195]


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See also in sourсe #XX -- [ Pg.1117 , Pg.1118 ]




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State lower oxidation states

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