Carbon–hydrogen bond activation a C-H activation. Carbon–hydrogen bond activation Carbon–hydrogen bond functionalization (C–H functionalization) is a type of reaction in which a carbon–hydrogen bond is cleaved and replaced with a carbon-X bond (where X is usually carbon, oxygen, or nitrogen). The term usually implies that a transition metal is involved in the C-H cleavage process. Reactions classified by the term typically involve the hydrocarbon first to react with a metal catalyst to create an organometallic complex in which the hydrocarbon is coordinated to the inner-sphere of a metal, either via an intermediate "alkane or arene complex" or as a transition state leading to
Carbon–hydrogen bond activation by a rhodium complex. In the case of alkanes, exclusive terminal functionalization was observed. Later, ruthenium catalysts were discovered to have higher activity and functional group compatibility. Other borylation catalysts have also been developed, including iridium-based catalysts, which successfully activate C-H bonds with high compatibility. For more information, consult borylation. No applications have been commercialized for homogeneously catalyzed C-H activations. Naturally occurring methane is not utilized as a chemical feedstock, despite its abundance and low cost. Current technology makes prodigious use of methane by steam reforming to produce syngas, a mixture of carbon monoxide and hydrogen. This syngas is then