K2FeH4(SO5)2 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 9-coordinate geometry to one O(2), one O(4), one O(5), one O(7), one O(9), two equivalent O(1), and two equivalent O(3) atoms. In the second K site, K(2) is bonded in a 9-coordinate geometry to one H(3), one O(10), one O(4), one O(5), one O(7), two equivalent O(6), and two equivalent O(8) atoms. Fe(1) is bonded to one O(1), one O(10), one O(4), one O(5), one O(8), and one O(9) atom to form FeO6 octahedra that share corners with two equivalent S(1)O4 tetrahedra and corners with two equivalent S(2)O4 tetrahedra. There are four inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one O(9) atom. In the second H site, H(2) is bonded in a single-bond geometry to one O(6) and one O(9) atom. In the third H site, H(3) is bonded in a single-bond geometry to one K(2) and one O(10) atom. In the fourth H site, H(4) is bonded in a single-bond geometry to one O(10) atom. There are two inequivalent S sites. In the first S site, S(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form SO4 tetrahedra that share corners with two equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 44-45°. In the second S site, S(2) is bonded to one O(5), one O(6), one O(7), and one O(8) atom to form SO4 tetrahedra that share corners with two equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 40-48°. There are ten inequivalent O sites. In the first O site, O(1) is bonded in a 2-coordinate geometry to two equivalent K(1), one Fe(1), and one S(1) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to one K(1) and one S(1) atom. In the third O site, O(3) is bonded in a distorted single-bond geometry to two equivalent K(1) and one S(1) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one K(1), one K(2), one Fe(1), and one S(1) atom. In the fifth O site, O(5) is bonded in a 4-coordinate geometry to one K(1), one K(2), one Fe(1), and one S(2) atom. In the sixth O site, O(6) is bonded in a 4-coordinate geometry to two equivalent K(2), one H(2), and one S(2) atom. In the seventh O site, O(7) is bonded in a distorted single-bond geometry to one K(1), one K(2), and one S(2) atom. In the eighth O site, O(8) is bonded in a 3-coordinate geometry to two equivalent K(2), one Fe(1), and one S(2) atom. In the ninth O site, O(9) is bonded in a distorted water-like geometry to one K(1), one Fe(1), one H(1), and one H(2) atom. In the tenth O site, O(10) is bonded in a distorted water-like geometry to one K(2), one Fe(1), one H(3), and one H(4) atom.
K2FeH4(SO5)2 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 9-coordinate geometry to one O(2), one O(4), one O(5), one O(7), one O(9), two equivalent O(1), and two equivalent O(3) atoms. The K(1)-O(2) bond length is 2.86 Å. The K(1)-O(4) bond length is 2.92 Å. The K(1)-O(5) bond length is 2.77 Å. The K(1)-O(7) bond length is 3.03 Å. The K(1)-O(9) bond length is 2.84 Å. There is one shorter (2.96 Å) and one longer (3.05 Å) K(1)-O(1) bond length. There is one shorter (2.81 Å) and one longer (2.89 Å) K(1)-O(3) bond length. In the second K site, K(2) is bonded in a 9-coordinate geometry to one H(3), one O(10), one O(4), one O(5), one O(7), two equivalent O(6), and two equivalent O(8) atoms. The K(2)-H(3) bond length is 2.91 Å. The K(2)-O(10) bond length is 2.91 Å. The K(2)-O(4) bond length is 2.88 Å. The K(2)-O(5) bond length is 2.89 Å. The K(2)-O(7) bond length is 2.84 Å. There is one shorter (2.82 Å) and one longer (2.84 Å) K(2)-O(6) bond length. There is one shorter (2.76 Å) and one longer (3.27 Å) K(2)-O(8) bond length. Fe(1) is bonded to one O(1), one O(10), one O(4), one O(5), one O(8), and one O(9) atom to form FeO6 octahedra that share corners with two equivalent S(1)O4 tetrahedra and corners with two equivalent S(2)O4 tetrahedra. The Fe(1)-O(1) bond length is 2.17 Å. The Fe(1)-O(10) bond length is 2.13 Å. The Fe(1)-O(4) bond length is 2.14 Å. The Fe(1)-O(5) bond length is 2.17 Å. The Fe(1)-O(8) bond length is 2.20 Å. The Fe(1)-O(9) bond length is 2.18 Å. There are four inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one O(9) atom. The H(1)-O(9) bond length is 0.99 Å. In the second H site, H(2) is bonded in a single-bond geometry to one O(6) and one O(9) atom. The H(2)-O(6) bond length is 1.69 Å. The H(2)-O(9) bond length is 1.00 Å. In the third H site, H(3) is bonded in a single-bond geometry to one K(2) and one O(10) atom. The H(3)-O(10) bond length is 0.99 Å. In the fourth H site, H(4) is bonded in a single-bond geometry to one O(10) atom. The H(4)-O(10) bond length is 0.98 Å. There are two inequivalent S sites. In the first S site, S(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form SO4 tetrahedra that share corners with two equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 44-45°. The S(1)-O(1) bond length is 1.51 Å. The S(1)-O(2) bond length is 1.49 Å. The S(1)-O(3) bond length is 1.48 Å. The S(1)-O(4) bond length is 1.51 Å. In the second S site, S(2) is bonded to one O(5), one O(6), one O(7), and one O(8) atom to form SO4 tetrahedra that share corners with two equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 40-48°. The S(2)-O(5) bond length is 1.52 Å. The S(2)-O(6) bond length is 1.49 Å. The S(2)-O(7) bond length is 1.48 Å. The S(2)-O(8) bond length is 1.50 Å. There are ten inequivalent O sites. In the first O site, O(1) is bonded in a 2-coordinate geometry to two equivalent K(1), one Fe(1), and one S(1) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to one K(1) and one S(1) atom. In the third O site, O(3) is bonded in a distorted single-bond geometry to two equivalent K(1) and one S(1) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one K(1), one K(2), one Fe(1), and one S(1) atom. In the fifth O site, O(5) is bonded in a 4-coordinate geometry to one K(1), one K(2), one Fe(1), and one S(2) atom. In the sixth O site, O(6) is bonded in a 4-coordinate geometry to two equivalent K(2), one H(2), and one S(2) atom. In the seventh O site, O(7) is bonded in a distorted single-bond geometry to one K(1), one K(2), and one S(2) atom. In the eighth O site, O(8) is bonded in a 3-coordinate geometry to two equivalent K(2), one Fe(1), and one S(2) atom. In the ninth O site, O(9) is bonded in a distorted water-like geometry to one K(1), one Fe(1), one H(1), and one H(2) atom. In the tenth O site, O(10) is bonded in a distorted water-like geometry to one K(2), one Fe(1), one H(3), and one H(4) atom.