Stannous compounds

Zinnozydul, n. stannous oxide, tin(II) oxide, -chlorid, n. stannous chloride, tin(II) chloride. -hydrat, n. stannous hydroxide, tin(II) hydroxide, -natron, n. sodium stannite. -reserve, /. stannous oxide resist, -salz, n. stannous salt, tin(II) salt, -verbindimg, /. stannous compound, tin(II) compound. 

The situation for tin-119 is more confused because of the uncertainty in AR/R. The first attempts to systematize isomer shifts for tin-119 were made by Cordey-Hayes and his co-workers (8). He assumed that ionic stannous compounds have a configuration 5s, Sn compounds or tetrahedral tin compounds have the configuration in which there are 4 p ... 

Compounds in which tin is covalently bonded lie near the center of the diagram—gray tin and several organometallic compounds. Stannic compounds lie in a comparatively narrow group near —2 mm./sec., while stannous compounds lie in a large band to the right of zero. 

One immediate question appears why the wide range of isomer shifts for stannous compounds The tin ions cannot be in the ideal Sn (5s ) state. What is happening All of these compounds have complicated crystal structures, with tin located at a site which does not have inversion symmetry there is an electric field acting at the site of the tin. This electric field produces matrix elements between the 5s and the 5p states of the tin and therefore a mixing of the two states. The ground state under these circumstances is not a pure 5s state, but a mixture of 5s and 5p. This is confirmed by studying the quadrupole splitting of... 

Relation between isomer shift and quadrupole splitting for stannous compounds (13)... 

The problem of the sign of AR/R for the divalent tin compounds was investigated by Lees and Flinn (16). In the relationship between the quadrupole splitting and chemical shift for the stannous compounds, two distinct correlations became apparent—compounds with a linear covalent bond, and compounds with a predominantly planar bond. Furthermore, there exists a linear relationship between the number of 5 p electrons and the chemical shift and hence the total 5 electron density. Using free tin ion wave functions in a self-consistent field calculation, they showed that the direct eflEect of adding 5 electrons is considerably... 

Chemical shift in stannous compounds Lees, Flinn + 16... 

Btaunio eompounds(tee TiA), Stannous compounds (see Xin), Statical formulm, 20,... 

Tin forms two series of compounds tin(II) or stannous compounds and tint IV1 or stannic compounds. Tin(ll) oxide, SnO, insoluble in water, is formed by precipitation of an SnO hydrate from an S11CL solution with alkali and later treatment in water (near the boiling point and at constant pH). It is amphiprotic, but only slightly acid, forming stannites slowly with strong alkalis. Sodium stannite is conveniently prepared from... 

Tin has a marked tendency to develop the valence 4 characteristic of the group, and in consequence stannous compounds are strong reducing agents. 

The elements Si, Ge, Sn, and Pb all exhibit the oxidation states of +2 and +4. However, the +2 state for Si is rare. One reason is that SiO is not stable and the halides SiF2 and SiCl2 are polymeric solids. A few Ge(II) compounds are known (e.g., GeO, GeS, and Gel2). The +2 and +4 oxidation states are about equally common for Sn and Pb. For example, Sn02 is the most common ore of Sn, and numerous compounds contain Sn(II) (stannous compounds). As we will see later, there are also numerous common compounds of both Pb(II) and Pb(IV). 

The tin(II) or stannous compounds are usually colourless. In acid solution the tin(II) ions Sn2+ are present, while in alkaline solutions tetrahydroxo-stannate(II) or stannite ions [Sn(OH)4]2- are to be found. These two are readily transformed into each other ... 

Discussion of Experiment 174. — Stannous compounds readily form stannic compounds, i.c. by an extension of the conception of oxidation and reduction, they reduce... 

Compounds of divalent Ge are well known. There is no evidence that GeO is a stable phase at temperatures below 1000°K (compare SiO), but compounds stable at ordinary temperatures include GeS, all four dihalides, and complex halides such as MGeCla. The Ge ion is not stable in water, and its crystal structure shows that GeF2 is not a simple ionic crystal (p. 929). There seem to be no simple ionic crystalline stannous compounds. In solution Sn presumably exists as complexes its easy conversion into Sn" gives stannous compounds their reducing properties. Lead presents a quite different picture. The stable ion is Pb . This has no reducing properties, and there is no evidence that Pb can exist in aqueous solution, but it certainly exists in crystalline compounds such as Pb02 (rutile structure). 

FIG. 26.12. Halogen-metal complexes in stannous compounds (a) (SnCl2(HjO)] HjO, (b) KSnFs. iH20, (c) NaSn2Fj, (d) NaaSnsFio. 

Elemental tin has an atomic number of 50, an atomic mass of 118.69, and exists in three allotropic forms white tin at room temperature, nonmetallic gray tin at <13.3°C, and brittle tin at >161°C. White tin is a stable silver-white, lustrous, soft metal with a density of 7.27, a melting point of 231.9°C, and a boiling point of 2507°C. Tin has 10 stable isotopes ( Sn, Sn, Sn, Sn, Sn, Sn, Sn, °Sn, Sn, and " Sn), the most for any element. Inorganic tin compounds exist in the +2 (stannous) and +A (stannic) oxidation states. Stannous compounds are generally more polar than stannic compounds, are unstable in dilute aqueous solutions, are easily oxidized, and normally contain some Sn+". Stannic oxide occurs naturally as the mineral cassiterite, has a melting point of 1127°C, and has wide application in industry. 

Inorganic tin and its salts are not highly toxic due to their poor absorption, relative insolubility of their oxides, and rapid tissue turnover. The absorption of ingested inorgaiuc tin is usually less than 5%, although up to 20% has been reported. Stannous compounds are more readily absorbed from the gastrointestinal tract than staimic compounds, but absorbed tin leaves the... 

The structures of three stannous compounds have been reported. In stannous sulphate, the tin atom has the typical pyramidal configuration with the lone pair occupying the fourth site of a pseudo-tetrahedron. " The Sn-O distances to the bridging sulphate ions are 2.246—2.273 A. Each tin atom also has nine other Sn O contacts in the range 2.949—3.336 A. 

Ketones are prepared by the carbonylation of aromatic or aliphatic halides in the presence of tetra-alkyl stannous compounds. 

An interesting propargylic ketone synthesis has been published by T. Kobayashi [34] which avoids these stannous compounds ... 

Reaction (36) was discovered by Arbuzov more than a century ago (not with PVC). It reflects the strength of P(iii) as a reducing agent, the product, P(v) bearing a P=0 bond. This is the primary color retention contribution of the phosphite component. Reaction (36) is catalyzed by zinc and cadmium salts, and probably by stannous compounds. 

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