Stannic ion

The main binary tin fluorides are stannous fluoride and stannic fluoride. Because the stannous ion,, is readily oxidized to the stannic ion,, most reported tin and fluorine complexes are of tin(IV) and fluorostannates. Stannous fluoroborates have also been reported. 

Although it is possible, by the loss of several electrons, for certain metal atoms to form polyvalent cations upto a maximum valency of four (e.g., tin forms the tetravalent stannic ion, Sn4+), the formation of polyvalent anions is extremely difficult since for the acquisition of each additional electron the attractive force exerted by the nucleus on each individual electron becomes progressively smaller. It is for this reason that the maximum valency for a simple anion is found to be two. 

One also sees that at room temperature the two peaks of the quadru-pole split pattern are different in intensity. This difference disappears at 77°K. It is an example of what is known as the Gordanskii effect 10) and is caused by the fact that the amplitude of vibration is different, parallel to the surface and normal to the surface, so that the effective resonant fraction is different for the two halves of the quadrupole splitting. This effect has been extensively studied by the Russians. In a recent paper, Suzdalev and others report a study of tin in the surface of silica gel 18), They put calcium ions in the surface of silica gel, then replaced them with divalent tin by ion exchange. The result was a mixture of stannous and stannic ions, and of course, the use of the Mossbauer effect made it possible to determine accurately the relative amounts of the two. They studied the amplitude of vibration of the two kinds of atoms and found, for example, for the stannous ions, the r.m.s. amplitude of vibration parallel to the surface was 0.07 A., and the r.m.s. amplitude of vibration perpendicular to the surface was about twice as great—about 0.13 A. Karasev and others have also worked on the chemistry of adsorbed... 

Compare the reducing properties of stannous and stannic ions. 

When a suitable inert electrode (usually a platinum one, sometimes also of gold) is immersed into a solution, containing e. g. the ions of stanneous and stannic salt, it can be observed that the electrode attains a certain potential the value of which depends on the ratio of the activities of ions Sn++ and Sn+ ++. In a solution containing predominantly stannic ions beside a small amount of stannous ones, stannic ions show a tendency to be converted into stanneous ions by acquiring electrons from the platinum electrode ... 

In a method that predates the Stock system, two different endings are used to distinguish the valences of metals. The ending -ic is used to represent the larger valence number. The ending -ous is used to represent the smaller valence number. Thus, the ions Sn2+ and Sn4+ are named stannous ion and stannic ion. To use this system, you need to know the Latin name of an element. For example, the two ions of lead are the plumbous and plumbic ions. See Table 3.6 for more examples. 

Aqua regia dissolves tin readily, when again tin(IV) (stannic) ions are formed ... 

This low value of the equilibrium constant means that when equilibrium is attained in the ferrous-ferric and stannous-stannic mixture, the concentrations (activities) of ferric and stannous ions must be negligibly small in comparison with those of the ferrous and stannic ions. In other words, when these two systems are mixed, reaction occurs so that the ferric ions are virtually completely reduced to ferrous ions while the stannous are oxidized to stannic ions. This fact is utilized in analytical work for the reduction of ferric to ferrous ions prior to the estimation of the latter by means of dichromate. 

The next step is to balance the ecjnation for the reaction. In balancing the equation for an oxidation-reduction reaction it is often vise to write the electron reactions separately (as they would occur in an electrolytic cell), and then to add them so as to cancel out the electrons. For example, ferric ion, Fe- +", oxidi/es stannous ion, Sn, to stannic ion, Sn + + + + that is, from the bipositive state to the quadripositive state. The ferric ion is itsell reduced to ferrous ion, Fe++. The two electron reactions are... 

A novel reduction was discovered by Baumstark,126 involving the reaction of dioxetane lb with stannous chloride, leading to pinacol and stannic ion on hydrolysis [Eq. (52)]. Formally it could be considered as... 

Test a dilute solution of your product for chloride ions. Also test for stannic ions by adding ammonia and observing whether any hydrated tin dioxide is precipitated. 

The net Fceii = 1 -74 V — 0.13V = - -1.61V. The emf (A) of the half-cell is given by the Nernst equation for a stannous/stannic half-cell, with the stannous ion oxidizing to stannic ion ... 

The reduction of nitrobenzene to aniline is a typical oxidation-reduction reaction in which tin metal, Sn°, is oxidized to stannic ion, Sn, in the form of stannic chloride, SnCl4 hydrochloric acid serves as the source of protons. A plausible mechanism of this reaction is outlined in Scheme 21.3. Generally, the reduction occurs by a sequence of steps in which an electron is first transferred from a tin atom to the organic substrate to give an intermediate radical ion that is then protonated. The oxygen atoms on the nitro group are eventually removed as water molecules. It is left as an exercise to write a balanced equation for the overall reaction and to provide a mechanism for the reduction of N-phenylhydroxylamine (11) into aniline (see Exercises 13 and 14 at the end of this section). 

Write the balanced half-reactions for the reduction of nitrobenzene (5) into aniline (6) and for the oxidation of tin metal into stannic ion, Sn. Sum these equations and write the balanced equation for the overall process. 

Nearly all anions can enter into complex formation with metal ions. Thus stannic chloride, SnCU, forms with chloride ion the stable hexachloro-stannic ion, SnCle, which with cations crystallizes in an extensive series of salts. Various complexes of this kind are discussed below. Many chloride complexes are known representative are the following ... 

Study of the Titration Curve of Stannic Ions by Chromous Ions—Generalization to All Asymmetrical Titrations... 

The mechanism for the polymerization of VCM in the presence of TBPO-stannous octoate may be described as follows. The t-butoxy radical adds to VCM and initiates polymerization, in lieu of hydrogen abstraction. The reaction between the substrate radical (i.e., a VCM radical or the propagating chain radical) and the stannic ion results in the termination of the radical chain reaction and regeneration of the stannous ion. Thus, the latter is available for decomposition of BPO to generate additional chain-mitiating t-butoxy radicals. However, the termination of chain growth results in an inefficient consumption of radicals ... 

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