K2H2P2O7 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 4-coordinate geometry to one O(1), one O(2), one O(5), and one O(6) atom. In the second K site, K(2) is bonded in a 6-coordinate geometry to one O(2), one O(3), one O(4), one O(7), and two equivalent O(1) atoms. There are two inequivalent P sites. In the first P site, P(1) is bonded in a tetrahedral geometry to one O(2), one O(3), one O(4), and one O(7) atom. In the second P site, P(2) is bonded in a distorted trigonal non-coplanar geometry to one O(4), one O(5), and one O(6) atom. There are two inequivalent H sites. In the first H site, H(1) is bonded in a linear geometry to one O(3) and one O(5) atom. In the second H site, H(2) is bonded in a linear geometry to one O(2) and one O(6) atom. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one K(1), two equivalent K(2), and one O(7) atom. In the second O site, O(2) is bonded in a 4-coordinate geometry to one K(1), one K(2), one P(1), and one H(2) atom. In the third O site, O(3) is bonded in a water-like geometry to one K(2), one P(1), and one H(1) atom. In the fourth O site, O(4) is bonded in a distorted bent 150 degrees geometry to one K(2), one P(1), and one P(2) atom. In the fifth O site, O(5) is bonded in a 2-coordinate geometry to one K(1), one P(2), and one H(1) atom. In the sixth O site, O(6) is bonded in a distorted trigonal planar geometry to one K(1), one P(2), and one H(2) atom. In the seventh O site, O(7) is bonded in a distorted single-bond geometry to one K(2), one P(1), and one O(1) atom.
K2H2P2O7 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 4-coordinate geometry to one O(1), one O(2), one O(5), and one O(6) atom. The K(1)-O(1) bond length is 2.57 Å. The K(1)-O(2) bond length is 2.73 Å. The K(1)-O(5) bond length is 2.73 Å. The K(1)-O(6) bond length is 2.65 Å. In the second K site, K(2) is bonded in a 6-coordinate geometry to one O(2), one O(3), one O(4), one O(7), and two equivalent O(1) atoms. The K(2)-O(2) bond length is 2.72 Å. The K(2)-O(3) bond length is 3.13 Å. The K(2)-O(4) bond length is 3.35 Å. The K(2)-O(7) bond length is 2.81 Å. There is one shorter (2.73 Å) and one longer (2.99 Å) K(2)-O(1) bond length. There are two inequivalent P sites. In the first P site, P(1) is bonded in a tetrahedral geometry to one O(2), one O(3), one O(4), and one O(7) atom. The P(1)-O(2) bond length is 1.51 Å. The P(1)-O(3) bond length is 1.57 Å. The P(1)-O(4) bond length is 1.58 Å. The P(1)-O(7) bond length is 1.60 Å. In the second P site, P(2) is bonded in a distorted trigonal non-coplanar geometry to one O(4), one O(5), and one O(6) atom. The P(2)-O(4) bond length is 1.77 Å. The P(2)-O(5) bond length is 1.56 Å. The P(2)-O(6) bond length is 1.64 Å. There are two inequivalent H sites. In the first H site, H(1) is bonded in a linear geometry to one O(3) and one O(5) atom. The H(1)-O(3) bond length is 1.08 Å. The H(1)-O(5) bond length is 1.42 Å. In the second H site, H(2) is bonded in a linear geometry to one O(2) and one O(6) atom. The H(2)-O(2) bond length is 1.62 Å. The H(2)-O(6) bond length is 1.02 Å. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one K(1), two equivalent K(2), and one O(7) atom. The O(1)-O(7) bond length is 1.50 Å. In the second O site, O(2) is bonded in a 4-coordinate geometry to one K(1), one K(2), one P(1), and one H(2) atom. In the third O site, O(3) is bonded in a water-like geometry to one K(2), one P(1), and one H(1) atom. In the fourth O site, O(4) is bonded in a distorted bent 150 degrees geometry to one K(2), one P(1), and one P(2) atom. In the fifth O site, O(5) is bonded in a 2-coordinate geometry to one K(1), one P(2), and one H(1) atom. In the sixth O site, O(6) is bonded in a distorted trigonal planar geometry to one K(1), one P(2), and one H(2) atom. In the seventh O site, O(7) is bonded in a distorted single-bond geometry to one K(2), one P(1), and one O(1) atom.