When synthesizing simple organolithium reagents, the reduction of one equivalent of a simple alkyl or aryl halide with two equivalents of lithium metal produces one equivalent of a simple alkyl- or aryl-lithium and one equivalent of lithium halide with good yield.
This reaction is known to proceed via a radical pathway that is likely initiated through a single-electron-transfer mechanism of the type shown below.
Magnesium similarly metalates organohalides to give Grignard reagents.