Imido

Imido is a term used in chemistry to describe a nitrogen-centered fragment that functions as a ligand or substituent in two closely related contexts: organometallic/inorganic chemistry and certain organic frameworks.

In organometallic and inorganic chemistry, an imido ligand is a nitrogen-containing fragment bonded to a metal, commonly represented as M=NR or M=NR′. The imido group behaves as a nitrene equivalent, bringing a high-valent M–N multiple bond into the complex. Imido ligands can be terminal, bound to a single metal center, or bridging two metals. They are well known in early-transition-metal and actinide chemistry and can be generated by reactions such as dehydrogenation of amide precursors or by transfer of a nitrene equivalent from precursors like organoazides to a metal halide, often with loss of nitrogen gas.

In a broader sense, the term imido also appears in organic and inorganic frameworks to denote nitrogen-containing fragments derived from nitrene chemistry or imide-related structures, where nitrogen bears substituents and is part of a double-bonded or high-valent fragment within a molecular framework. The terminology is distinguished from imide, which refers to two carbonyl groups attached to nitrogen, and from nitrene, a neutral NR fragment.

Applications of imido-containing complexes include catalysis and selective transformations, where M=NR bonds enable various nitrogen-transfer reactions, C–H activations, and related processes.