K2In12Se19 crystallizes in the trigonal R-3 space group. K(1) is bonded in a 6-coordinate geometry to three equivalent Se(1) and three equivalent Se(2) atoms. There are two inequivalent In sites. In the first In site, In(1) is bonded to one Se(2), one Se(3), and two equivalent Se(1) atoms to form InSe4 tetrahedra that share corners with two equivalent In(1)Se4 tetrahedra and corners with four equivalent In(2)Se5 trigonal bipyramids. In the second In site, In(2) is bonded to one Se(4), two equivalent Se(2), and two equivalent Se(3) atoms to form InSe5 trigonal bipyramids that share corners with four equivalent In(1)Se4 tetrahedra, corners with three equivalent In(2)Se5 trigonal bipyramids, and edges with three equivalent In(2)Se5 trigonal bipyramids. There are four inequivalent Se sites. In the first Se site, Se(1) is bonded in a trigonal non-coplanar geometry to one K(1) and two equivalent In(1) atoms. In the second Se site, Se(2) is bonded to one K(1), one In(1), and two equivalent In(2) atoms to form distorted SeKIn3 tetrahedra that share corners with two equivalent Se(4)In6 octahedra, corners with two equivalent Se(2)KIn3 tetrahedra, and  an edgeedge with one Se(2)KIn3 tetrahedra. The corner-sharing octahedral tilt angles range from 3-82°. In the third Se site, Se(3) is bonded in a trigonal non-coplanar geometry to one In(1) and two equivalent In(2) atoms. In the fourth Se site, Se(4) is bonded to six equivalent In(2) atoms to form distorted corner-sharing SeIn6 octahedra.
K2In12Se19 crystallizes in the trigonal R-3 space group. K(1) is bonded in a 6-coordinate geometry to three equivalent Se(1) and three equivalent Se(2) atoms. All K(1)-Se(1) bond lengths are 3.44 Å. All K(1)-Se(2) bond lengths are 3.60 Å. There are two inequivalent In sites. In the first In site, In(1) is bonded to one Se(2), one Se(3), and two equivalent Se(1) atoms to form InSe4 tetrahedra that share corners with two equivalent In(1)Se4 tetrahedra and corners with four equivalent In(2)Se5 trigonal bipyramids. The In(1)-Se(2) bond length is 2.66 Å. The In(1)-Se(3) bond length is 2.71 Å. Both In(1)-Se(1) bond lengths are 2.58 Å. In the second In site, In(2) is bonded to one Se(4), two equivalent Se(2), and two equivalent Se(3) atoms to form InSe5 trigonal bipyramids that share corners with four equivalent In(1)Se4 tetrahedra, corners with three equivalent In(2)Se5 trigonal bipyramids, and edges with three equivalent In(2)Se5 trigonal bipyramids. The In(2)-Se(4) bond length is 3.24 Å. There is one shorter (2.60 Å) and one longer (3.02 Å) In(2)-Se(2) bond length. There is one shorter (2.62 Å) and one longer (2.65 Å) In(2)-Se(3) bond length. There are four inequivalent Se sites. In the first Se site, Se(1) is bonded in a trigonal non-coplanar geometry to one K(1) and two equivalent In(1) atoms. In the second Se site, Se(2) is bonded to one K(1), one In(1), and two equivalent In(2) atoms to form distorted SeKIn3 tetrahedra that share corners with two equivalent Se(4)In6 octahedra, corners with two equivalent Se(2)KIn3 tetrahedra, and  an edgeedge with one Se(2)KIn3 tetrahedra. The corner-sharing octahedral tilt angles range from 3-82°. In the third Se site, Se(3) is bonded in a trigonal non-coplanar geometry to one In(1) and two equivalent In(2) atoms. In the fourth Se site, Se(4) is bonded to six equivalent In(2) atoms to form distorted corner-sharing SeIn6 octahedra.