In 1868 a French man by Marcel-Paul Schützenberger (a mathematician who also studied medicine) began a new form of organic complexes by creating the first metal carbonyl complex.  These complexes gain importance through the catalytic reactions of Carbon monoxide, which is a piece in the creation of many molecules of biological importance.  The bonding of the CO with the metal is also of some relevance due to the unique character (not shown in the picture below) where the orbitals of the metal bond with the pi-orbitals of the C≡O.  The complex, Dicarbonyldichloroplatinum [Pt(CO)₂Cl₂] was formed through him passing carbon monoxide and chlorine over powdered Platinum (also known as Platinum black).