Disclosed herein are novel platinum-based complexes possessing one nitrile substituent group (mononitrile) covalently-bonded to the platinum, one or more nitrogen donor ligands capable of forming hydrogen bonds with the bases in DNA or RNA and leaving groups (i.e., L<;SUB>;1 <;/SUB>;and L<;SUB>;2<;/SUB>;) which can be hydrolyzed in vivo to active species, which can then form coordinate adducts with DNA or RNA at the Guanine or Adenine bases thereof. Also disclosed herein are the reaction schemes for the synthesis of said platinum complexes, as well as methods of treatment of various types of cancer by the administration of a pharmaceutically-effective dose of said novel platinum complexes.