Transition metal cyanate complexes are coordination complexes containing one or more cyanate (NCO−) ligands. Many complexes are known for this venerable ligand.
Structure and bonding
Cyanate is a pseudohalide. As reflected by the pKa's of cyanic acid (3.7) and hydrochloric acid (-5.9), cyanate is more basic than chloride. As a monodentate ligand, cyanate generally binds metals through the nitrogen atom, i.e., M-N=C=O. It is a sigma donor. It is classified as an X ligand in the Covalent bond classification method. In the usual electron counting method, it is a one-electron ligand.
The NCO unit is linear or nearly so in cyanate complexes. The M-N-C angles can be quite bent or nearly linear. The bond distances determined by X-ray crystallography support the description [N=C=O]-.
Examples of homoleptic complexes are the tetrahedral dianions [Mn(NCO)4]2-, [Co(NCO)4]2-, and [Zn(NCO)4]2-.
Preparation Metal cyanate complexes can be prepared using alkali metal cyanate salts such as sodium cyanate and potassium cyanate.
The complex is prepared from treating the aquo complex with urea.
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