Studies of transuranic organometallic complexes provide particularly valuable insight into covalent contributions to the metal-ligand bonding, in which the subtle differences between the transuranium AnIII ions and their lighter lanthanide LnIII counterparts are of fundamental importance for effective remediation of nuclear waste. Unlike the organometallic chemistry of uranium, which has focused strongly on UIII with spectacular advances, that of the transuranics is significantly technically more challenging and has remained dormant. In the case of neptunium, it is limited mainly to NpIV. Here we report a range of new NpIII organometallics, and characterize their molecular and electronic structures. These studies suggest that the lower oxidation state of NpII is chemically accessible, and that NpIII complexes could act as single molecule magnets. Significant d- and f-electron contributions to key NpIII orbitals are found in comparison with lanthanide analogues, showing that fundamental Np organometallic chemistry can provide new insight into f-element behaviour.