Metal salen complex

A metal salen complex is a coordination compound between a metal cation and a ligand derived from N,N′-bis(salicylidene)ethylenediamine, commonly called salen. The classical example is salcomine, the complex with divalent cobalt Co²⁺, usually denoted as Co(salen). These complexes are widely investigated as catalysts and enzyme mimics.

The metal-free salen compound (H₂salen or salenH₂) has two phenolic hydroxyl groups. The salen ligand is usually its conjugate base (salen²⁻), resulting from the loss of protons from those hydroxyl groups. The metal atom usually makes four coordination bonds to the oxygen and nitrogen atoms.