Iodide tetravalency

Westheimer has also reviewed the induced oxidations by the Cr(VI)-As(III) couple of iodide, bromide and manganous ions vide supra). The induction factor of 0.5 for Mn(II) implies an intermediate tetravalent chromium species however, the factor of 2 for iodide points to a pentavalent chromium intermediate. Both... 

Good yields are obtained only if the oxidation of the divalent lead to the tetravalent stage is complete. To test for plumbous lead, add ten drops of the reaction mixture to five milliliters of water and boil gently for a few minutes to hydrolyze all the tetravalent lead to lead dioxide. When the latter settles, filter the hot mixture, cool under the tap, and add several drops of saturated potassium iodide. A yellow precipitate of lead iodide constitutes a positive test. 

Oxidizing reagents such as tetravalent cerium or potassium permanganate solutions may be standardized by oxalic acid, sodium oxalate, or potassium iodide. The reactions of Ce4+ and permanganate ions with oxalic acid in acid medium are given below ... 

Attempted oxidative addition reactions involving Pb[CH(SiMe3)2]2 did not yield stable tetravalent products as shown in Eq. (41) and (42) (78). Reaction with methyl iodide shown in Eq. (42) resulted in rapid disappearance of the purple color due to Pb[CH(SiMe3)2]2 followed by slow precipitation of Pbl2. 

Tetravalent plutonium in aq soln is reduced to the trivalent form by sulfur dioxide, hydroxylamine hydrochloride, hydrazine hydrochloride, the uranous ion, the iodide ion by shaking with mercury in chloride soln electrolytically at a platinum cathode. Tetravalent salts are pink or greenish form complexes very readily. 

A radical mechanism, on the other hand, is also conceivable. In this case, iodide would begin by transferring a single electron to arsenic acid, producing a tetravalent As intermediate, which could fall apart in a number of ways, one of which is shown below ... 

All divalent, trivalent, and tetravalent chlorides, bromides, and iodides are hygroscopic and an appreciable solution chemistry has been characterized, but only aspects of solution chemistry that relate to hydrates are considered here. The solid-state chemistry of the lower oxidation states (to IV) of cations in combination with the F, Cl, Br, and I atoms, and combinations of these with main-group cations is considered. The numerous reactions some of these halides undergo with organic reagents and solvents are considered only to the extent they relate to solid-state chemistry. 

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