Tin—mercury bonds

Mercury-tin bonds are readily cleaved by the halogens to yield haloorganotins. The bulky complex Hg[Sn CH(Bu-r) 3]2 reacts with HgCl2, iodine and Hg(CH2COOMe)2 to give the respective tin-chloride (90% yield), -iodide (74% yield) and -methyl acetate (88% yield)364. 

It is a colourless gas which decomposes on heating above 420 K to give metallic tin, often deposited as a mirror, and hydrogen. It is a reducing agent and will reduce silver ions to silver and mercury(II) ions to mercury. SnSn bonding is unknown in hydrides but does exist in alkyl and aryl compounds, for example (CH3)3Sn-Sn(CH3)3. 

Like mercury, tin is a metal that has a tendency to form covalent bonds with organic groups. The compounds to be discussed here are tributyl derivatives of tetravalent tin. The general formula for them is... 

Lewis acids based on boronic acid derivatives or main group elements such as mercury, tin and silicon form strong bonds to anions with considerable covalency, exemplified by hydride sponge and the anticrowns. 

Vinyllead and alkynyllead tricarboxylates can only be prepared by metal-metal exchange, such as mercury-lead,ll6 ll7 tin-lead,ll6,ll7 boron-lead i or zinc-lead.l In the case of tin-lead exchange, cleavage of the methyl-tin bond is much slower than cleavage of the vinyl-tin or alkynyl-tin bond. Therefore (trimethyl)vinyltin derivatives are preferred to the corresponding (tributyl)vinyltin analogues for the synthesis of the unstable vinyllead and alkynyllead compounds. 

As seen above, compounds of the type R2Fe(CO)4 with iron-carbon a bonds are known only when R is a perfluoroalkyl radical or a maleoyl radical. However, compounds of this type where the iron atom is a-bonded to an element other than carbon, are somewhat more common. Derivatives are known in which the iron atom is cr-bonded to gold, mercury, tin, and lead. 

New compounds in this chapter are mercury containing phenates, a manganese complex previously reported with a manganese-tin bond and the ensuing oxa-stannacyclopentane. All bis(organotin)alkoxides are included in this chapter. 

The reaction has also been used to prepare 1,3-dilithiopropanes" and 1,1-dilithio-methylenecyclohexane" from the corresponding mercury compounds. In general, the equilibrium lies in the direction in which the more electropositive metal is bonded to that alkyl or aryl group that is the more stable carbanion (p. 228). The reaction proceeds with retention of configuration an Sgi mechanism is likely. Higher order cuprates (see Ref. 1277 in Chapter 10) have been produced by this reaction starting with a vinylic tin compound ... 

The Addition of Tin and Mercury Hydrides to Activated Double Bonds... 

Again several alkyls add—molybdenum, chromium, iron, cobalt, nickel, the alkali metal alkyls and aluminum alkyls react. A tin alkoxide has recently been studied by Russian workers and found to add to acetylenes. Mercury chloride, of course, adds and two cobalt—cobalt bonded compounds add to acetylene. The second is questionable because it dissociates in solution and the reaction may be a radical reaction, one cobalt adding to each end of the triple bond. 

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