The Ternary Post-transition Metal Carbodiimide SrZn(NCN)2

SrZn(NCN)(2), the first example of a ternary post-transition metal carbodiimide, was prepared by a solid-state metathesis reaction. The crystal structure was solved from PXRD data and found to adopt the orthorhombic (Cmcm) BaZnSO structure, a high symmetry modification of that expressed by the oxide analogue SrZnO2. Locally, SrZn(NCN)(2) features ZnN4 tetrahedra and SrN6 trigonal prisms similar to those in quarternary LiSr2M(NCN)(4) (M = Al3+ and Ga3+) phases, however, the overall topologies are distinct with single chains in the former and double chains in the latter. Electronic structure calculations indicate an indirect bandgap of about 2.95 eV in SrZn(NCN)(2), slightly lower than the experimentally observed bandgap of 3.4 eV in SrZnO2 and consistent with a greater degree of covalency. The structural similarities between SrZn(NCN)(2) and oxychalcogenide analogues highlight the pseudochalcogenide character of NCN2- and suggest that the title compound may serve as a template for accessing novel ternary carbodiimides featuring tetrahedrally coordinated transition metals.