Carbon-hydrogen activation reactions are very much what the name would imply— they break typically unreactive carbon-hydrogen bonds. Considering the prevalence of carbon-hydrogen bonds in organic compounds, this is another extremely important type of reaction to be able to carry out both effectively and with selectivity. Successful examples of carbon-hydrogen bond activation reactions have only come about relatively recently (with the first genuine example reported ca. 1965), and organometallic reagents have played a key role in the development of carbon-hydrogen bond reactions.