Platinum 1-4 oxidation state

Effect of Platinum Oxidation State in the Catalytic Oxidation of Cyclohexene... 

They prove that the platinum oxidation state can be finely varied without causing important structural changes, but for a progressive elongation of the Pt-Pt distance with the decrease of the overall charge. 

A platinum oxidation state of +2.30 was determined by iodine-thiosulfate titrations9 assuming a molecular weight of 662.44. The calculated Pt oxidation state, based on the chemical analyses and crystallographic analysis, is +2.38 0.02. °... 

Hall MD, Foran GJ, Zhang M, Beale PJ, Hambley TW. XANES Determination of the Platinum Oxidation State Distribution in Cancer Cells Treated with Platinum(IV) Anticancer Agents. J. Am. Chem. Soc. 2003 125 7524-7525. 

Thermogravimetric analyses indicate that the compound contains 1.8 mole water. The tentatively accepted platinum oxidation state is +2.27 based on the fluorine content of the compound and has an estimated standard deviation of 0.02. Iodine thiosulfate titrations indicate a platinum oxidation state of +2.26.8... 

After 2 hours of electrolysis10 at 1.5 V, the product, having filled the bottom of the beaker, is filtered in a plastic funnel. The crystals are then washed with two 6-mL portions of cold water and allowed to air dry. The yield of 1.4-1.5 g (3.2-3.4mmole) represents 88-94% based on original K2[Pt(CN)4] 3H20. Using X-ray diffraction powder patterns, it is established that the products of both syntheses given above are identical.8 The platinum oxidation state of 2.29(1) is established by iodine-thiosulfate titrations.8... 

Chemical analyses and theoretical values are reported in Table I.8 The calculated platinum oxidation state, based on chemical analysis and crystallographic analysis, is +2.25. An X-ray diffuse scattering analysis also indicates that the Pt oxidation state is 2.25(2).ls... 

All these platinum complexes exhibit very strong antitumor activity, suggesting that the platinum oxidation state of either Pt" or does not determine the quality of antitumor activity. In general, the activity of platinum(IV) complexes is somewhat smaller than that of platinum(II) complexes. It might well be that the activity of platinum(IV) is, in fact, that of platinum(II), in which case the reduction occurs in vivo, probably by the action of cysteine. ... 

Figure Bl.25.3. Pt 4f XPS spectra of platinum metal (top) and of the two organoplatinmn compounds (a) and (b), middle and bottom respectively, shown in figure B 1.25.2, illustrating that the Pt 4f bmding energy reflects the oxidation state of platinum (from [9]).

Bromine has a lower electron affinity and electrode potential than chlorine but is still a very reactive element. It combines violently with alkali metals and reacts spontaneously with phosphorus, arsenic and antimony. When heated it reacts with many other elements, including gold, but it does not attack platinum, and silver forms a protective film of silver bromide. Because of the strong oxidising properties, bromine, like fluorine and chlorine, tends to form compounds with the electropositive element in a high oxidation state. 

These elements formed Group IIB of Mendeleef s original periodic table. As we have seen in Chapter 13, zinc does not show very marked transition-metaf characteristics. The other two elements in this group, cadmium and mercury, lie at the ends of the second and third transition series (Y-Cd, La-Hg) and, although they resemble zinc in some respects in showing a predominantly - - 2 oxidation state, they also show rather more transition-metal characteristics. Additionally, mercury has characteristics, some of which relate it quite closely to its immediate predecessors in the third transition series, platinum and gold, and some of which are decidedly peculiar to mercury. 

Some metals used as metallic coatings are considered nontoxic, such as aluminum, magnesium, iron, tin, indium, molybdenum, tungsten, titanium, tantalum, niobium, bismuth, and the precious metals such as gold, platinum, rhodium, and palladium. However, some of the most important poUutants are metallic contaminants of these metals. Metals that can be bioconcentrated to harmful levels, especially in predators at the top of the food chain, such as mercury, cadmium, and lead are especially problematic. Other metals such as silver, copper, nickel, zinc, and chromium in the hexavalent oxidation state are highly toxic to aquatic Hfe (37,57—60). 

Oxidation catalysts are either metals that chemisorb oxygen readily, such as platinum or silver, or transition metal oxides that are able to give and take oxygen by reason of their having several possible oxidation states. Ethylene oxide is formed with silver, ammonia is oxidized with platinum, and silver or copper in the form of metal screens catalyze the oxidation of methanol to formaldehyde. Cobalt catalysis is used in the following oxidations butane to acetic acid and to butyl-hydroperoxide, cyclohexane to cyclohexylperoxide, acetaldehyde to acetic acid and toluene to benzoic acid. PdCh-CuCb is used for many liquid-phase oxidations and V9O5 combinations for many vapor-phase oxidations. 

This method involves very simple and inexpensive equipment that could be set up m any laboratory [9, 10] The equipment consists of a 250-mL beaker (used as an external half-cell), two platinum foil electrodes, a glass tube with asbestos fiber sealed m the bottom (used as an internal half-cell), a microburet, a stirrer, and a portable potentiometer The asbestos fiber may be substituted with a membrane This method has been used to determine the fluoride ion concentration in many binary and complex fluondes and has been applied to unbuffered solutions from Willard-Winter distillation, to lon-exchange eluant, and to pyrohydrolysis distil lates obtained from oxygen-flask or tube combustions The solution concentrations range from 0 1 to 5 X 10 M This method is based on complexing by fluonde ions of one of the oxidation states of the redox couple, and the potential difference measured is that between the two half-cells Initially, each cell contains the same ratio of cerium(IV) and cerium(tll) ions... 

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