K2W2O15 crystallizes in the triclinic P-1 space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 8-coordinate geometry to one O(10), one O(12), one O(14), one O(15), one O(7), one O(9), and two equivalent O(2) atoms. In the second K site, K(2) is bonded in a 6-coordinate geometry to one O(13), one O(3), one O(4), one O(6), one O(7), and one O(9) atom. There are two inequivalent W sites. In the first W site, W(1) is bonded to one O(1), one O(10), one O(11), one O(4), and one O(9) atom to form distorted corner-sharing WO5 trigonal bipyramids. In the second W site, W(2) is bonded to one O(11), one O(12), one O(13), one O(5), one O(6), one O(7), and one O(8) atom to form distorted WO7 pentagonal bipyramids that share  a cornercorner with one O(7)K2WO tetrahedra and  a cornercorner with one W(1)O5 trigonal bipyramid. There are fifteen inequivalent O sites. In the first O site, O(1) is bonded in a distorted water-like geometry to one W(1) and one O(2) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to two equivalent K(1) and one O(1) atom. In the third O site, O(3) is bonded in a distorted bent 150 degrees geometry to one K(2) and one O(4) atom. In the fourth O site, O(4) is bonded in a trigonal planar geometry to one K(2), one W(1), and one O(3) atom. In the fifth O site, O(5) is bonded in a 2-coordinate geometry to one W(2) and one O(6) atom. In the sixth O site, O(6) is bonded in a distorted T-shaped geometry to one K(2), one W(2), and one O(5) atom. In the seventh O site, O(7) is bonded to one K(1), one K(2), one W(2), and one O(8) atom to form distorted OK2WO tetrahedra that share  a cornercorner with one W(2)O7 pentagonal bipyramid. In the eighth O site, O(8) is bonded in a 2-coordinate geometry to one W(2) and one O(7) atom. In the ninth O site, O(9) is bonded in a distorted single-bond geometry to one K(1), one K(2), and one W(1) atom. In the tenth O site, O(10) is bonded in a bent 150 degrees geometry to one K(1) and one W(1) atom. In the eleventh O site, O(11) is bonded in a bent 150 degrees geometry to one W(1) and one W(2) atom. In the twelfth O site, O(12) is bonded in a distorted single-bond geometry to one K(1) and one W(2) atom. In the thirteenth O site, O(13) is bonded in a bent 120 degrees geometry to one K(2) and one W(2) atom. In the fourteenth O site, O(14) is bonded in a bent 120 degrees geometry to one K(1) and one O(15) atom. In the fifteenth O site, O(15) is bonded in a bent 150 degrees geometry to one K(1) and one O(14) atom.
K2W2O15 crystallizes in the triclinic P-1 space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 8-coordinate geometry to one O(10), one O(12), one O(14), one O(15), one O(7), one O(9), and two equivalent O(2) atoms. The K(1)-O(10) bond length is 2.65 Å. The K(1)-O(12) bond length is 3.04 Å. The K(1)-O(14) bond length is 2.98 Å. The K(1)-O(15) bond length is 3.10 Å. The K(1)-O(7) bond length is 2.74 Å. The K(1)-O(9) bond length is 3.13 Å. There is one shorter (2.79 Å) and one longer (3.13 Å) K(1)-O(2) bond length. In the second K site, K(2) is bonded in a 6-coordinate geometry to one O(13), one O(3), one O(4), one O(6), one O(7), and one O(9) atom. The K(2)-O(13) bond length is 2.68 Å. The K(2)-O(3) bond length is 3.00 Å. The K(2)-O(4) bond length is 3.08 Å. The K(2)-O(6) bond length is 2.94 Å. The K(2)-O(7) bond length is 2.75 Å. The K(2)-O(9) bond length is 2.90 Å. There are two inequivalent W sites. In the first W site, W(1) is bonded to one O(1), one O(10), one O(11), one O(4), and one O(9) atom to form distorted corner-sharing WO5 trigonal bipyramids. The W(1)-O(1) bond length is 2.09 Å. The W(1)-O(10) bond length is 1.77 Å. The W(1)-O(11) bond length is 1.92 Å. The W(1)-O(4) bond length is 2.12 Å. The W(1)-O(9) bond length is 1.77 Å. In the second W site, W(2) is bonded to one O(11), one O(12), one O(13), one O(5), one O(6), one O(7), and one O(8) atom to form distorted WO7 pentagonal bipyramids that share  a cornercorner with one O(7)K2WO tetrahedra and  a cornercorner with one W(1)O5 trigonal bipyramid. The W(2)-O(11) bond length is 1.95 Å. The W(2)-O(12) bond length is 1.81 Å. The W(2)-O(13) bond length is 1.83 Å. The W(2)-O(5) bond length is 2.10 Å. The W(2)-O(6) bond length is 2.16 Å. The W(2)-O(7) bond length is 2.22 Å. The W(2)-O(8) bond length is 2.12 Å. There are fifteen inequivalent O sites. In the first O site, O(1) is bonded in a distorted water-like geometry to one W(1) and one O(2) atom. The O(1)-O(2) bond length is 1.34 Å. In the second O site, O(2) is bonded in a 3-coordinate geometry to two equivalent K(1) and one O(1) atom. In the third O site, O(3) is bonded in a distorted bent 150 degrees geometry to one K(2) and one O(4) atom. The O(3)-O(4) bond length is 1.33 Å. In the fourth O site, O(4) is bonded in a trigonal planar geometry to one K(2), one W(1), and one O(3) atom. In the fifth O site, O(5) is bonded in a 2-coordinate geometry to one W(2) and one O(6) atom. The O(5)-O(6) bond length is 1.36 Å. In the sixth O site, O(6) is bonded in a distorted T-shaped geometry to one K(2), one W(2), and one O(5) atom. In the seventh O site, O(7) is bonded to one K(1), one K(2), one W(2), and one O(8) atom to form distorted OK2WO tetrahedra that share  a cornercorner with one W(2)O7 pentagonal bipyramid. The O(7)-O(8) bond length is 1.35 Å. In the eighth O site, O(8) is bonded in a 2-coordinate geometry to one W(2) and one O(7) atom. In the ninth O site, O(9) is bonded in a distorted single-bond geometry to one K(1), one K(2), and one W(1) atom. In the tenth O site, O(10) is bonded in a bent 150 degrees geometry to one K(1) and one W(1) atom. In the eleventh O site, O(11) is bonded in a bent 150 degrees geometry to one W(1) and one W(2) atom. In the twelfth O site, O(12) is bonded in a distorted single-bond geometry to one K(1) and one W(2) atom. In the thirteenth O site, O(13) is bonded in a bent 120 degrees geometry to one K(2) and one W(2) atom. In the fourteenth O site, O(14) is bonded in a bent 120 degrees geometry to one K(1) and one O(15) atom. The O(14)-O(15) bond length is 1.23 Å. In the fifteenth O site, O(15) is bonded in a bent 150 degrees geometry to one K(1) and one O(14) atom.