K4Sn9 is Magnesium tetraboride-like structured and crystallizes in the monoclinic P2_1/c space group. There are four inequivalent K sites. In the first K site, K(1) is bonded in a 7-coordinate geometry to one Sn(3), one Sn(4), one Sn(5), one Sn(6), one Sn(7), and two equivalent Sn(8) atoms. In the second K site, K(2) is bonded in a 7-coordinate geometry to one Sn(3), one Sn(4), one Sn(5), two equivalent Sn(6), and two equivalent Sn(8) atoms. In the third K site, K(3) is bonded in a 8-coordinate geometry to one Sn(4), one Sn(5), one Sn(7), two equivalent Sn(1), two equivalent Sn(2), and two equivalent Sn(9) atoms. In the fourth K site, K(4) is bonded in a 8-coordinate geometry to one Sn(2), one Sn(3), one Sn(4), one Sn(5), one Sn(6), one Sn(9), and two equivalent Sn(1) atoms. There are nine inequivalent Sn sites. In the first Sn site, Sn(9) is bonded in a 8-coordinate geometry to one K(4), two equivalent K(3), one Sn(1), one Sn(2), one Sn(3), one Sn(5), and one Sn(7) atom. In the second Sn site, Sn(1) is bonded in a 8-coordinate geometry to two equivalent K(3), two equivalent K(4), one Sn(2), one Sn(4), one Sn(7), and one Sn(9) atom. In the third Sn site, Sn(2) is bonded in a 8-coordinate geometry to one K(4), two equivalent K(3), one Sn(1), one Sn(4), one Sn(5), one Sn(8), and one Sn(9) atom. In the fourth Sn site, Sn(3) is bonded in a 8-coordinate geometry to one K(1), one K(2), one K(4), one Sn(5), one Sn(6), one Sn(7), one Sn(8), and one Sn(9) atom. In the fifth Sn site, Sn(4) is bonded in a 8-coordinate geometry to one K(1), one K(2), one K(3), one K(4), one Sn(1), one Sn(2), one Sn(6), and one Sn(8) atom. In the sixth Sn site, Sn(5) is bonded in a 8-coordinate geometry to one K(1), one K(2), one K(3), one K(4), one Sn(2), one Sn(3), one Sn(8), and one Sn(9) atom. In the seventh Sn site, Sn(6) is bonded in a 8-coordinate geometry to one K(1), one K(4), two equivalent K(2), one Sn(3), one Sn(4), one Sn(7), and one Sn(8) atom. In the eighth Sn site, Sn(7) is bonded in a 6-coordinate geometry to one K(1), one K(3), one Sn(1), one Sn(3), one Sn(6), and one Sn(9) atom. In the ninth Sn site, Sn(8) is bonded in a 9-coordinate geometry to two equivalent K(1), two equivalent K(2), one Sn(2), one Sn(3), one Sn(4), one Sn(5), and one Sn(6) atom.
K4Sn9 is Magnesium tetraboride-like structured and crystallizes in the monoclinic P2_1/c space group. There are four inequivalent K sites. In the first K site, K(1) is bonded in a 7-coordinate geometry to one Sn(3), one Sn(4), one Sn(5), one Sn(6), one Sn(7), and two equivalent Sn(8) atoms. The K(1)-Sn(3) bond length is 3.77 Å. The K(1)-Sn(4) bond length is 4.02 Å. The K(1)-Sn(5) bond length is 3.73 Å. The K(1)-Sn(6) bond length is 3.66 Å. The K(1)-Sn(7) bond length is 3.84 Å. There is one shorter (3.67 Å) and one longer (3.94 Å) K(1)-Sn(8) bond length. In the second K site, K(2) is bonded in a 7-coordinate geometry to one Sn(3), one Sn(4), one Sn(5), two equivalent Sn(6), and two equivalent Sn(8) atoms. The K(2)-Sn(3) bond length is 3.69 Å. The K(2)-Sn(4) bond length is 3.70 Å. The K(2)-Sn(5) bond length is 4.07 Å. There is one shorter (3.64 Å) and one longer (3.81 Å) K(2)-Sn(6) bond length. There is one shorter (3.51 Å) and one longer (3.87 Å) K(2)-Sn(8) bond length. In the third K site, K(3) is bonded in a 8-coordinate geometry to one Sn(4), one Sn(5), one Sn(7), two equivalent Sn(1), two equivalent Sn(2), and two equivalent Sn(9) atoms. The K(3)-Sn(4) bond length is 3.59 Å. The K(3)-Sn(5) bond length is 4.12 Å. The K(3)-Sn(7) bond length is 3.82 Å. There is one shorter (3.71 Å) and one longer (3.97 Å) K(3)-Sn(1) bond length. There is one shorter (3.69 Å) and one longer (3.81 Å) K(3)-Sn(2) bond length. There is one shorter (3.75 Å) and one longer (3.90 Å) K(3)-Sn(9) bond length. In the fourth K site, K(4) is bonded in a 8-coordinate geometry to one Sn(2), one Sn(3), one Sn(4), one Sn(5), one Sn(6), one Sn(9), and two equivalent Sn(1) atoms. The K(4)-Sn(2) bond length is 3.87 Å. The K(4)-Sn(3) bond length is 4.07 Å. The K(4)-Sn(4) bond length is 3.61 Å. The K(4)-Sn(5) bond length is 4.10 Å. The K(4)-Sn(6) bond length is 4.09 Å. The K(4)-Sn(9) bond length is 4.12 Å. There is one shorter (3.80 Å) and one longer (3.93 Å) K(4)-Sn(1) bond length. There are nine inequivalent Sn sites. In the first Sn site, Sn(9) is bonded in a 8-coordinate geometry to one K(4), two equivalent K(3), one Sn(1), one Sn(2), one Sn(3), one Sn(5), and one Sn(7) atom. The Sn(9)-Sn(1) bond length is 3.03 Å. The Sn(9)-Sn(2) bond length is 3.29 Å. The Sn(9)-Sn(3) bond length is 3.17 Å. The Sn(9)-Sn(5) bond length is 3.05 Å. The Sn(9)-Sn(7) bond length is 3.07 Å. In the second Sn site, Sn(1) is bonded in a 8-coordinate geometry to two equivalent K(3), two equivalent K(4), one Sn(2), one Sn(4), one Sn(7), and one Sn(9) atom. The Sn(1)-Sn(2) bond length is 3.04 Å. The Sn(1)-Sn(4) bond length is 3.06 Å. The Sn(1)-Sn(7) bond length is 3.01 Å. In the third Sn site, Sn(2) is bonded in a 8-coordinate geometry to one K(4), two equivalent K(3), one Sn(1), one Sn(4), one Sn(5), one Sn(8), and one Sn(9) atom. The Sn(2)-Sn(4) bond length is 3.04 Å. The Sn(2)-Sn(5) bond length is 2.99 Å. The Sn(2)-Sn(8) bond length is 3.21 Å. In the fourth Sn site, Sn(3) is bonded in a 8-coordinate geometry to one K(1), one K(2), one K(4), one Sn(5), one Sn(6), one Sn(7), one Sn(8), and one Sn(9) atom. The Sn(3)-Sn(5) bond length is 2.98 Å. The Sn(3)-Sn(6) bond length is 3.03 Å. The Sn(3)-Sn(7) bond length is 3.06 Å. The Sn(3)-Sn(8) bond length is 3.38 Å. In the fifth Sn site, Sn(4) is bonded in a 8-coordinate geometry to one K(1), one K(2), one K(3), one K(4), one Sn(1), one Sn(2), one Sn(6), and one Sn(8) atom. The Sn(4)-Sn(6) bond length is 3.04 Å. The Sn(4)-Sn(8) bond length is 2.99 Å. In the sixth Sn site, Sn(5) is bonded in a 8-coordinate geometry to one K(1), one K(2), one K(3), one K(4), one Sn(2), one Sn(3), one Sn(8), and one Sn(9) atom. The Sn(5)-Sn(8) bond length is 3.01 Å. In the seventh Sn site, Sn(6) is bonded in a 8-coordinate geometry to one K(1), one K(4), two equivalent K(2), one Sn(3), one Sn(4), one Sn(7), and one Sn(8) atom. The Sn(6)-Sn(7) bond length is 3.04 Å. The Sn(6)-Sn(8) bond length is 2.98 Å. In the eighth Sn site, Sn(7) is bonded in a 6-coordinate geometry to one K(1), one K(3), one Sn(1), one Sn(3), one Sn(6), and one Sn(9) atom. In the ninth Sn site, Sn(8) is bonded in a 9-coordinate geometry to two equivalent K(1), two equivalent K(2), one Sn(2), one Sn(3), one Sn(4), one Sn(5), and one Sn(6) atom.