Potassium carbamoyldicyanomethanide

The crystal structure of the title compound, K[(CN)(2)CC(O)NH2)] or K+.C4H2N3O-, conventionally abbreviated as Kcdm, where cdm is carbamoyldicyanomethanide, is described. The bond lengths and angles of the cdm cation are comparable to those reported previously for [M(cdm)(2)(H2O)(4)].2H(2)O (M=Ni, Mn and Co). The K atoms are coordinated to four nitrile N atoms and two carbonyl O atoms in a distorted trigonal prismatic fashion, with two further N atoms semicoordinated through the centers of two prism side faces. This coordination leads to the formation of mixed anion-cation sheets parallel to the ab plane, which are joined together via hydrogen-bonding interactions. The cdm anion is potentially useful for the formation of transition metal coordination polymers, in which magnetic superexchange could occur through a bidentate cdm bridge. Kcdm provides a model compound by which the molecular geometry of the cdm anion can be analyzed.