Based on the results of the author’s own diploma thesis, several neutron diffraction experiments have been carried out to determine the antiferromagnetic structure of MnNCN. In the ordered state, two different orientations of the manganese spins could be detected. With the preparation of CoNCN and NiNCN, two hitherto unknown transition metal carbodiimides were synthesized by a newly developed synthesis method via the corresponding hydrogencyanamides M(HNCN)_2. The crystal structure of the isotypical compounds CoNCN and NiNCN determined from single crystal data sets can be described as a variation of the NiAs structure elongated in c direction. Magnetic measurements show significantly reduced effective magnetic moments compared to dilute systems and maxima of susceptibility at comparatively high temperature. Both aspects are signs of very strong antiferromagnetic interactions between the metal ions. The hydrogencyanamides mentioned above are also new compounds and the first ones of their kind containing cations with unpaired electrons. The determination of the magnetic properties showed them to be ferromagnetic with very low Curie points. For CdNCN, Raman data were recorded, whereby the structure published before could be clearly refuted. Both nitrogen atoms were determined to show exactly the same distance to the carbon atom, and the shape of the anion is linear. The NCN2- unit consequently adopts the carbodiimide conformation. Thus, the reported C–N and Cd–N bond lengths could be corrected
