Tetraethyllead, Pb (C2H5)4
Tetraethyllead is an example of an organometallic compound - where one or more orgainc groups are attached to a metal atom. In this case lead has four ethyl- groups arranged tetrahedrally around it. It is the organic groups which are of interest here. Pb-C bonds are relatively weak, and the ethyl- groups of this compound, which is a fuel additive, fall off the lead when inside an internal combustion engine. On combustion of petrol containing this additive particles of lead and lead(II) oxide are formed. These slow down certain steps in the combustion process and prevent "knocking". These are uncontrolled explosions which can damage car engines. The lead is very poisonous and harms both people and the catalytic converters which are used to reduce other noxoius emissions.
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