CoSi2N3 crystallizes in the orthorhombic Cmc2_1 space group. Co(1) is bonded in a distorted rectangular see-saw-like geometry to two equivalent N(1) and two equivalent N(2) atoms. Si(1) is bonded to one N(2) and three equivalent N(1) atoms to form corner-sharing SiN4 tetrahedra. There are two inequivalent N sites. In the first N site, N(2) is bonded to two equivalent Co(1) and two equivalent Si(1) atoms to form distorted NCo2Si2 trigonal pyramids that share corners with ten equivalent N(1)CoSi3 tetrahedra and corners with two equivalent N(2)Co2Si2 trigonal pyramids. In the second N site, N(1) is bonded to one Co(1) and three equivalent Si(1) atoms to form distorted NCoSi3 tetrahedra that share corners with seven equivalent N(1)CoSi3 tetrahedra and corners with five equivalent N(2)Co2Si2 trigonal pyramids.
CoSi2N3 crystallizes in the orthorhombic Cmc2_1 space group. Co(1) is bonded in a distorted rectangular see-saw-like geometry to two equivalent N(1) and two equivalent N(2) atoms. Both Co(1)-N(1) bond lengths are 2.36 Å. There is one shorter (1.97 Å) and one longer (2.04 Å) Co(1)-N(2) bond length. Si(1) is bonded to one N(2) and three equivalent N(1) atoms to form corner-sharing SiN4 tetrahedra. The Si(1)-N(2) bond length is 1.71 Å. There is one shorter (1.76 Å) and two longer (1.78 Å) Si(1)-N(1) bond lengths. There are two inequivalent N sites. In the first N site, N(2) is bonded to two equivalent Co(1) and two equivalent Si(1) atoms to form distorted NCo2Si2 trigonal pyramids that share corners with ten equivalent N(1)CoSi3 tetrahedra and corners with two equivalent N(2)Co2Si2 trigonal pyramids. In the second N site, N(1) is bonded to one Co(1) and three equivalent Si(1) atoms to form distorted NCoSi3 tetrahedra that share corners with seven equivalent N(1)CoSi3 tetrahedra and corners with five equivalent N(2)Co2Si2 trigonal pyramids.