Y2Mo4O15 crystallizes in the monoclinic P2_1/c space group. Y(1) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), one O(6), and one O(7) atom to form YO7 pentagonal bipyramids that share corners with two equivalent Mo(2)O5 tetrahedra, corners with four equivalent Mo(1)O4 tetrahedra, and  an edgeedge with one Mo(2)O5 tetrahedra. There are two inequivalent Mo sites. In the first Mo site, Mo(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form MoO4 tetrahedra that share corners with four equivalent Y(1)O7 pentagonal bipyramids and  a cornercorner with one Mo(2)O5 tetrahedra. In the second Mo site, Mo(2) is bonded to one O(4), one O(5), one O(6), one O(7), and one O(8) atom to form distorted MoO5 tetrahedra that share corners with two equivalent Y(1)O7 pentagonal bipyramids,  a cornercorner with one Mo(1)O4 tetrahedra,  a cornercorner with one Mo(2)O5 tetrahedra, and  an edgeedge with one Y(1)O7 pentagonal bipyramid. There are eight inequivalent O sites. In the first O site, O(6) is bonded in a bent 150 degrees geometry to one Y(1) and one Mo(2) atom. In the second O site, O(7) is bonded in a bent 120 degrees geometry to one Y(1) and one Mo(2) atom. In the third O site, O(8) is bonded in a linear geometry to two equivalent Mo(2) atoms. In the fourth O site, O(1) is bonded in a linear geometry to one Y(1) and one Mo(1) atom. In the fifth O site, O(2) is bonded in a bent 150 degrees geometry to one Y(1) and one Mo(1) atom. In the sixth O site, O(3) is bonded in a bent 150 degrees geometry to one Y(1) and one Mo(1) atom. In the seventh O site, O(4) is bonded in a 3-coordinate geometry to one Y(1), one Mo(1), and one Mo(2) atom. In the eighth O site, O(5) is bonded in a distorted linear geometry to one Y(1) and one Mo(2) atom.
Y2Mo4O15 crystallizes in the monoclinic P2_1/c space group. Y(1) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), one O(6), and one O(7) atom to form YO7 pentagonal bipyramids that share corners with two equivalent Mo(2)O5 tetrahedra, corners with four equivalent Mo(1)O4 tetrahedra, and  an edgeedge with one Mo(2)O5 tetrahedra. The Y(1)-O(1) bond length is 2.30 Å. The Y(1)-O(2) bond length is 2.28 Å. The Y(1)-O(3) bond length is 2.30 Å. The Y(1)-O(4) bond length is 2.35 Å. The Y(1)-O(5) bond length is 2.39 Å. The Y(1)-O(6) bond length is 2.33 Å. The Y(1)-O(7) bond length is 2.38 Å. There are two inequivalent Mo sites. In the first Mo site, Mo(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form MoO4 tetrahedra that share corners with four equivalent Y(1)O7 pentagonal bipyramids and  a cornercorner with one Mo(2)O5 tetrahedra. The Mo(1)-O(1) bond length is 1.78 Å. The Mo(1)-O(2) bond length is 1.79 Å. The Mo(1)-O(3) bond length is 1.79 Å. The Mo(1)-O(4) bond length is 1.82 Å. In the second Mo site, Mo(2) is bonded to one O(4), one O(5), one O(6), one O(7), and one O(8) atom to form distorted MoO5 tetrahedra that share corners with two equivalent Y(1)O7 pentagonal bipyramids,  a cornercorner with one Mo(1)O4 tetrahedra,  a cornercorner with one Mo(2)O5 tetrahedra, and  an edgeedge with one Y(1)O7 pentagonal bipyramid. The Mo(2)-O(4) bond length is 2.56 Å. The Mo(2)-O(5) bond length is 1.77 Å. The Mo(2)-O(6) bond length is 1.77 Å. The Mo(2)-O(7) bond length is 1.78 Å. The Mo(2)-O(8) bond length is 1.90 Å. There are eight inequivalent O sites. In the first O site, O(6) is bonded in a bent 150 degrees geometry to one Y(1) and one Mo(2) atom. In the second O site, O(7) is bonded in a bent 120 degrees geometry to one Y(1) and one Mo(2) atom. In the third O site, O(8) is bonded in a linear geometry to two equivalent Mo(2) atoms. In the fourth O site, O(1) is bonded in a linear geometry to one Y(1) and one Mo(1) atom. In the fifth O site, O(2) is bonded in a bent 150 degrees geometry to one Y(1) and one Mo(1) atom. In the sixth O site, O(3) is bonded in a bent 150 degrees geometry to one Y(1) and one Mo(1) atom. In the seventh O site, O(4) is bonded in a 3-coordinate geometry to one Y(1), one Mo(1), and one Mo(2) atom. In the eighth O site, O(5) is bonded in a distorted linear geometry to one Y(1) and one Mo(2) atom.