A triclinic polymorph of catena-poly[[bis-(N,N-dimethyl-formamide-κO)cobalt(II)]-di-μ-1,5-dicyanamido-κ(4)N(1):N(5)].

The title compound, [Co(C(2)N(3))(2)(C(3)H(7)NO)(2)](n), is a triclinic polymorph of the previously reported monoclinic structure [Tong et al. (2003 ▶). Acta Cryst. E59, m405-m407]. The Co(II) ion lies on an inversion centre and adopts an almost regular octa-hedral N(4)O(2) coordination geometry. Adjacent Co(II) atoms are connected by two bridging dicyanamide ligands, resulting in the formation of neutral chains parallel to the b axis. The title complex is isotypic with the Mn(II) analogue but not with the Ni(II) analogue.