K2Mn(NbCl3)6 crystallizes in the trigonal R-3 space group. K(1) is bonded to three equivalent Cl(1), three equivalent Cl(2), and six equivalent Cl(3) atoms to form KCl12 cuboctahedra that share corners with three equivalent Mn(1)Cl6 octahedra, corners with six equivalent Nb(1)Cl5 square pyramids, edges with three equivalent K(1)Cl12 cuboctahedra, edges with three equivalent Nb(1)Cl5 square pyramids, and faces with three equivalent Nb(1)Cl5 square pyramids. The corner-sharing octahedral tilt angles are 51°. Nb(1) is bonded to one Cl(2), two equivalent Cl(1), and two equivalent Cl(3) atoms to form distorted NbCl5 square pyramids that share corners with two equivalent K(1)Cl12 cuboctahedra,  a cornercorner with one Mn(1)Cl6 octahedra, corners with four equivalent Nb(1)Cl5 square pyramids,  an edgeedge with one K(1)Cl12 cuboctahedra, and  a faceface with one K(1)Cl12 cuboctahedra. The corner-sharing octahedral tilt angles are 44°. Mn(1) is bonded to six equivalent Cl(2) atoms to form MnCl6 octahedra that share corners with six equivalent K(1)Cl12 cuboctahedra and corners with six equivalent Nb(1)Cl5 square pyramids. There are three inequivalent Cl sites. In the first Cl site, Cl(1) is bonded in a 3-coordinate geometry to one K(1) and two equivalent Nb(1) atoms. In the second Cl site, Cl(2) is bonded in a 3-coordinate geometry to one K(1), one Nb(1), and one Mn(1) atom. In the third Cl site, Cl(3) is bonded in a 4-coordinate geometry to two equivalent K(1) and two equivalent Nb(1) atoms.
K2Mn(NbCl3)6 crystallizes in the trigonal R-3 space group. K(1) is bonded to three equivalent Cl(1), three equivalent Cl(2), and six equivalent Cl(3) atoms to form KCl12 cuboctahedra that share corners with three equivalent Mn(1)Cl6 octahedra, corners with six equivalent Nb(1)Cl5 square pyramids, edges with three equivalent K(1)Cl12 cuboctahedra, edges with three equivalent Nb(1)Cl5 square pyramids, and faces with three equivalent Nb(1)Cl5 square pyramids. The corner-sharing octahedral tilt angles are 51°. All K(1)-Cl(1) bond lengths are 3.52 Å. All K(1)-Cl(2) bond lengths are 3.54 Å. There are three shorter (3.49 Å) and three longer (3.55 Å) K(1)-Cl(3) bond lengths. Nb(1) is bonded to one Cl(2), two equivalent Cl(1), and two equivalent Cl(3) atoms to form distorted NbCl5 square pyramids that share corners with two equivalent K(1)Cl12 cuboctahedra,  a cornercorner with one Mn(1)Cl6 octahedra, corners with four equivalent Nb(1)Cl5 square pyramids,  an edgeedge with one K(1)Cl12 cuboctahedra, and  a faceface with one K(1)Cl12 cuboctahedra. The corner-sharing octahedral tilt angles are 44°. The Nb(1)-Cl(2) bond length is 2.67 Å. Both Nb(1)-Cl(1) bond lengths are 2.47 Å. Both Nb(1)-Cl(3) bond lengths are 2.48 Å. Mn(1) is bonded to six equivalent Cl(2) atoms to form MnCl6 octahedra that share corners with six equivalent K(1)Cl12 cuboctahedra and corners with six equivalent Nb(1)Cl5 square pyramids. All Mn(1)-Cl(2) bond lengths are 2.61 Å. There are three inequivalent Cl sites. In the first Cl site, Cl(1) is bonded in a 3-coordinate geometry to one K(1) and two equivalent Nb(1) atoms. In the second Cl site, Cl(2) is bonded in a 3-coordinate geometry to one K(1), one Nb(1), and one Mn(1) atom. In the third Cl site, Cl(3) is bonded in a 4-coordinate geometry to two equivalent K(1) and two equivalent Nb(1) atoms.