Cs4Pb9 is Magnesium tetraboride-like structured and crystallizes in the monoclinic P2_1/c space group. There are four inequivalent Cs sites. In the first Cs site, Cs(1) is bonded in a 8-coordinate geometry to one Pb(1), one Pb(2), one Pb(3), one Pb(4), one Pb(5), one Pb(6), one Pb(7), one Pb(8), and one Pb(9) atom. In the second Cs site, Cs(2) is bonded in a 9-coordinate geometry to one Pb(1), one Pb(3), one Pb(6), one Pb(8), one Pb(9), two equivalent Pb(5), and two equivalent Pb(7) atoms. In the third Cs site, Cs(3) is bonded in a 10-coordinate geometry to one Pb(1), one Pb(3), one Pb(4), one Pb(6), one Pb(7), one Pb(9), two equivalent Pb(2), and two equivalent Pb(8) atoms. In the fourth Cs site, Cs(4) is bonded in a 8-coordinate geometry to one Pb(1), one Pb(2), one Pb(3), one Pb(4), one Pb(5), one Pb(6), one Pb(7), one Pb(8), and one Pb(9) atom. There are nine inequivalent Pb sites. In the first Pb site, Pb(8) is bonded in a 9-coordinate geometry to one Cs(1), one Cs(2), one Cs(4), two equivalent Cs(3), one Pb(1), one Pb(4), one Pb(5), and one Pb(7) atom. In the second Pb site, Pb(9) is bonded in a 9-coordinate geometry to one Cs(1), one Cs(2), one Cs(3), one Cs(4), one Pb(1), one Pb(2), one Pb(3), one Pb(4), and one Pb(6) atom. In the third Pb site, Pb(1) is bonded in a 8-coordinate geometry to one Cs(1), one Cs(2), one Cs(3), one Cs(4), one Pb(4), one Pb(6), one Pb(8), and one Pb(9) atom. In the fourth Pb site, Pb(2) is bonded in a 8-coordinate geometry to one Cs(1), one Cs(4), two equivalent Cs(3), one Pb(3), one Pb(4), one Pb(5), and one Pb(9) atom. In the fifth Pb site, Pb(3) is bonded in a 9-coordinate geometry to one Cs(1), one Cs(2), one Cs(3), one Cs(4), one Pb(2), one Pb(5), one Pb(6), one Pb(7), and one Pb(9) atom. In the sixth Pb site, Pb(4) is bonded in a 8-coordinate geometry to one Cs(1), one Cs(3), one Cs(4), one Pb(1), one Pb(2), one Pb(5), one Pb(8), and one Pb(9) atom. In the seventh Pb site, Pb(5) is bonded in a 9-coordinate geometry to one Cs(1), one Cs(4), two equivalent Cs(2), one Pb(2), one Pb(3), one Pb(4), one Pb(7), and one Pb(8) atom. In the eighth Pb site, Pb(6) is bonded in a 8-coordinate geometry to one Cs(1), one Cs(2), one Cs(3), one Cs(4), one Pb(1), one Pb(3), one Pb(7), and one Pb(9) atom. In the ninth Pb site, Pb(7) is bonded in a 9-coordinate geometry to one Cs(1), one Cs(3), one Cs(4), two equivalent Cs(2), one Pb(3), one Pb(5), one Pb(6), and one Pb(8) atom.
Cs4Pb9 is Magnesium tetraboride-like structured and crystallizes in the monoclinic P2_1/c space group. There are four inequivalent Cs sites. In the first Cs site, Cs(1) is bonded in a 8-coordinate geometry to one Pb(1), one Pb(2), one Pb(3), one Pb(4), one Pb(5), one Pb(6), one Pb(7), one Pb(8), and one Pb(9) atom. The Cs(1)-Pb(1) bond length is 4.13 Å. The Cs(1)-Pb(2) bond length is 3.87 Å. The Cs(1)-Pb(3) bond length is 3.94 Å. The Cs(1)-Pb(4) bond length is 4.07 Å. The Cs(1)-Pb(5) bond length is 4.16 Å. The Cs(1)-Pb(6) bond length is 4.01 Å. The Cs(1)-Pb(7) bond length is 4.55 Å. The Cs(1)-Pb(8) bond length is 3.93 Å. The Cs(1)-Pb(9) bond length is 4.16 Å. In the second Cs site, Cs(2) is bonded in a 9-coordinate geometry to one Pb(1), one Pb(3), one Pb(6), one Pb(8), one Pb(9), two equivalent Pb(5), and two equivalent Pb(7) atoms. The Cs(2)-Pb(1) bond length is 4.12 Å. The Cs(2)-Pb(3) bond length is 4.36 Å. The Cs(2)-Pb(6) bond length is 4.07 Å. The Cs(2)-Pb(8) bond length is 4.17 Å. The Cs(2)-Pb(9) bond length is 4.06 Å. There is one shorter (4.33 Å) and one longer (4.37 Å) Cs(2)-Pb(5) bond length. There is one shorter (4.06 Å) and one longer (4.32 Å) Cs(2)-Pb(7) bond length. In the third Cs site, Cs(3) is bonded in a 10-coordinate geometry to one Pb(1), one Pb(3), one Pb(4), one Pb(6), one Pb(7), one Pb(9), two equivalent Pb(2), and two equivalent Pb(8) atoms. The Cs(3)-Pb(1) bond length is 3.91 Å. The Cs(3)-Pb(3) bond length is 4.05 Å. The Cs(3)-Pb(4) bond length is 4.03 Å. The Cs(3)-Pb(6) bond length is 3.97 Å. The Cs(3)-Pb(7) bond length is 4.22 Å. The Cs(3)-Pb(9) bond length is 4.02 Å. There is one shorter (4.29 Å) and one longer (4.40 Å) Cs(3)-Pb(2) bond length. There is one shorter (4.34 Å) and one longer (4.53 Å) Cs(3)-Pb(8) bond length. In the fourth Cs site, Cs(4) is bonded in a 8-coordinate geometry to one Pb(1), one Pb(2), one Pb(3), one Pb(4), one Pb(5), one Pb(6), one Pb(7), one Pb(8), and one Pb(9) atom. The Cs(4)-Pb(1) bond length is 3.93 Å. The Cs(4)-Pb(2) bond length is 4.64 Å. The Cs(4)-Pb(3) bond length is 4.00 Å. The Cs(4)-Pb(4) bond length is 4.12 Å. The Cs(4)-Pb(5) bond length is 4.55 Å. The Cs(4)-Pb(6) bond length is 4.28 Å. The Cs(4)-Pb(7) bond length is 3.92 Å. The Cs(4)-Pb(8) bond length is 4.09 Å. The Cs(4)-Pb(9) bond length is 3.92 Å. There are nine inequivalent Pb sites. In the first Pb site, Pb(8) is bonded in a 9-coordinate geometry to one Cs(1), one Cs(2), one Cs(4), two equivalent Cs(3), one Pb(1), one Pb(4), one Pb(5), and one Pb(7) atom. The Pb(8)-Pb(1) bond length is 3.13 Å. The Pb(8)-Pb(4) bond length is 3.13 Å. The Pb(8)-Pb(5) bond length is 3.16 Å. The Pb(8)-Pb(7) bond length is 3.10 Å. In the second Pb site, Pb(9) is bonded in a 9-coordinate geometry to one Cs(1), one Cs(2), one Cs(3), one Cs(4), one Pb(1), one Pb(2), one Pb(3), one Pb(4), and one Pb(6) atom. The Pb(9)-Pb(1) bond length is 3.11 Å. The Pb(9)-Pb(2) bond length is 3.07 Å. The Pb(9)-Pb(3) bond length is 3.45 Å. The Pb(9)-Pb(4) bond length is 3.32 Å. The Pb(9)-Pb(6) bond length is 3.13 Å. In the third Pb site, Pb(1) is bonded in a 8-coordinate geometry to one Cs(1), one Cs(2), one Cs(3), one Cs(4), one Pb(4), one Pb(6), one Pb(8), and one Pb(9) atom. The Pb(1)-Pb(4) bond length is 3.18 Å. The Pb(1)-Pb(6) bond length is 3.15 Å. In the fourth Pb site, Pb(2) is bonded in a 8-coordinate geometry to one Cs(1), one Cs(4), two equivalent Cs(3), one Pb(3), one Pb(4), one Pb(5), and one Pb(9) atom. The Pb(2)-Pb(3) bond length is 3.08 Å. The Pb(2)-Pb(4) bond length is 3.11 Å. The Pb(2)-Pb(5) bond length is 3.14 Å. In the fifth Pb site, Pb(3) is bonded in a 9-coordinate geometry to one Cs(1), one Cs(2), one Cs(3), one Cs(4), one Pb(2), one Pb(5), one Pb(6), one Pb(7), and one Pb(9) atom. The Pb(3)-Pb(5) bond length is 3.28 Å. The Pb(3)-Pb(6) bond length is 3.14 Å. The Pb(3)-Pb(7) bond length is 3.11 Å. In the sixth Pb site, Pb(4) is bonded in a 8-coordinate geometry to one Cs(1), one Cs(3), one Cs(4), one Pb(1), one Pb(2), one Pb(5), one Pb(8), and one Pb(9) atom. The Pb(4)-Pb(5) bond length is 3.39 Å. In the seventh Pb site, Pb(5) is bonded in a 9-coordinate geometry to one Cs(1), one Cs(4), two equivalent Cs(2), one Pb(2), one Pb(3), one Pb(4), one Pb(7), and one Pb(8) atom. The Pb(5)-Pb(7) bond length is 3.18 Å. In the eighth Pb site, Pb(6) is bonded in a 8-coordinate geometry to one Cs(1), one Cs(2), one Cs(3), one Cs(4), one Pb(1), one Pb(3), one Pb(7), and one Pb(9) atom. The Pb(6)-Pb(7) bond length is 3.15 Å. In the ninth Pb site, Pb(7) is bonded in a 9-coordinate geometry to one Cs(1), one Cs(3), one Cs(4), two equivalent Cs(2), one Pb(3), one Pb(5), one Pb(6), and one Pb(8) atom.