trans-[Fe(CN) (CO) ] , a 21st Century [Fe(CN)(CO)] Compound.

In 1887, more than a century after the synthesis of [Fe (CN) ] , the complex [Fe (CN) (CO)] , in which a CN ligand is replaced by CO, was reported. It has taken an additional century for the synthesis of the complex in which a second CN ligand is substituted by CO: trans-[Fe (CN) (CO) ] (structure shown). Remarkably, this anion is prepared by the simple reaction of FeCl with NaCN and CO in water. [Fe(CN) (CO) ] complexes are of interest as models for the active site of hydrogenase enzymes.