No abstract

Synthesis, structure determination, and magnetic properties are reported for the metastable and crystal-chemically isotypic phases cobalt carbodiimide, CoNCN, and nickel carbodiimide, NiNCN, adopting the hexagonal system and space group P63/mmc (NiAs type) with interatomic distances of Co-N = 2.17 Angstrom and Ni-N = 2.12 Angstrom and an octahedral coordination of the transition-metal ions; the NCN(2-) units reveal the carbodiimide shape with two C=N double bonds. The low-susceptibility data go back to strong antiferromagnetic spin-spin coupling, similar to the behavior of the electronically related oxides CoO and NiO.

Synthesis, single-crystal structure determination, and magnetic properties are reported for manganese carbodiimide, MnNCN. The presumably unstable but inert phase adopts the trigonal system (R3m) with a = 3.3583(4) A, c = 14.347(2) A, V = 140.13(3) A3, and Z = 3. Divalent manganese is octahedrally coordinated by nitrogen atoms at 2.26 A, and the NCN(2-) unit adopts the linear [N=C=N](2-) carbodiimide shape with two C=N double bonds of 1.23 A. MnNCN contains high-spin Mn(II) with five unpaired electrons and behaves like an antiferromagnet with an ordering temperature below 30 K.

Iron man challenge: Iron carbodiimide, FeNCN, and its precursor iron (bis)monohydrocyanamide, Fe(NCNH)(2), have been synthesized and physically characterized. Both FeNCN and Fe(NCNH)(2) exhibit nitrogen-mediated antiferromagnetic superexchange interactions with reduced magnetic moments very similar, but not identical, to the correlated 3d oxides.