Carbon hydrides atomic mercury

A useful aspect of the mercury(II) hydride method is that it can be directly coupled with the many standard techniques for heteromercuration of alkenes and cyclopropanes. The resulting overall transformation adds a heteroatom and a carbon atom across the carbon-carbon double bond of an alkene or the carbon-carbon single bond of a cyclopropane. This is a difficult transformation to conduct by standard ionic techniques. An alkene thus becomes an equivalent of synthon (12) and a cyclopropane of synthon (13 Scheme 34). Many equivalent transformations (like haloetherification and phenylselenolactoniza-tion) are available to make precursors for tin hydride mediated additions. 

The organomercury radical extrudes mercury to produce a carbon radical which propagates the chain by abstracting a hydrogen atom from another molecule of hydride (path A). If the reaction is conducted in the deliberate presence of oxygen, the carbon radical can be captured to give ultimately an alcohol by reduction of the intermediate hydroperoxide (path B). 

Some organometallic compounds, for example, organomercury or organocobalt compounds, have very weak carbon-metal bonds, and are easily homolyzed to give carbon-centered radicals. Alkyl mercury hydrides are formed by reducing alkyl mercury halides, but they are unstable at room temperature because the Hg-H bond is very weak. Bonds to hydrogen never break to give radicals spontaneously because H" is too unstable to exist, but interaction with almost any radical removes the H atom and breaks the Hg-H bond (Scheme 4.9). 

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