Hello!

CN- is an organometallic compound but it can only be used as a nucleophile.

nucleophile is a species (an ion or a molecule) which is strongly attracted to a region of positive charge in something else.

Nucleophiles are either fully negative ions, or else have a strongly  partial - charge somewhere on a molecule.

In the case of the cyanide ion, there is a full negative charge on the carbon, as well as a lone pair of electrons.