methanide

Methanide refers to the methanide ion, CH3−, the conjugate base of methane. It is the simplest carbon-centered anion and is isoelectronic with ammonia. In solution it behaves as a very strong base and a reactive nucleophile, but free CH3− is not stable in water or other protic media.

Because methane has an extremely high pKa, CH3− is typically encountered only in nonaqueous environments or when bound to metal centers as a methanide ligand. In practice it is observed as alkali metal salts (for example, NaCH3 or KHCH3) or as a coordinated fragment in organometallic complexes. Such species are usually generated under highly controlled, inert conditions and are not isolated as a free ion in ordinary solvents.

As a reagent, methanide acts as a strong base and nucleophile. It can alkylate electrophiles or transfer the methanide fragment to metal centers to form M–CH3 bonds, which are relevant in various catalytic and synthetic processes. Its high basicity also drives deprotonation in suitable environments, though its use requires carefully chosen solvents and conditions to avoid rapid protonation or side reactions with trace water or oxygen.

In summary, methanide is a highly reactive, nonisolable anion under normal conditions, significant mainly as a reactive fragment in nonaqueous chemistry and in organometallic contexts where metal–methanide bonds are formed. Safety considerations include its extreme reactivity with moisture and air, necessitating inert, anhydrous handling.