K2MgNb2P2(CO7)2 crystallizes in the triclinic P1 space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 6-coordinate geometry to one O(13), one O(14), one O(2), one O(4), and two equivalent O(1) atoms. In the second K site, K(2) is bonded in a 5-coordinate geometry to one O(10), one O(12), one O(13), one O(14), and one O(8) atom. Mg(1) is bonded to one O(3), one O(5), one O(6), and one O(7) atom to form MgO4 tetrahedra that share  a cornercorner with one Nb(1)O6 octahedra,  a cornercorner with one Nb(2)O6 octahedra,  a cornercorner with one P(2)O4 tetrahedra, corners with two equivalent P(1)O4 tetrahedra, and  an edgeedge with one Nb(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 71-77°. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(2), one O(3), one O(4), one O(5), one O(6), and one O(8) atom to form distorted NbO6 octahedra that share  a cornercorner with one Mg(1)O4 tetrahedra, corners with two equivalent P(1)O4 tetrahedra, corners with two equivalent P(2)O4 tetrahedra, and  an edgeedge with one Mg(1)O4 tetrahedra. In the second Nb site, Nb(2) is bonded to one O(10), one O(11), one O(12), one O(13), one O(7), and one O(9) atom to form NbO6 octahedra that share  a cornercorner with one Mg(1)O4 tetrahedra, corners with two equivalent P(1)O4 tetrahedra, and corners with two equivalent P(2)O4 tetrahedra. There are two inequivalent C sites. In the first C site, C(1) is bonded in a trigonal planar geometry to one O(14), one O(2), and one O(3) atom. In the second C site, C(2) is bonded in a trigonal planar geometry to one O(1), one O(12), and one O(13) atom. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(4), one O(5), one O(7), and one O(9) atom to form PO4 tetrahedra that share corners with two equivalent Nb(1)O6 octahedra, corners with two equivalent Nb(2)O6 octahedra, and corners with two equivalent Mg(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 27-57°. In the second P site, P(2) is bonded to one O(10), one O(11), one O(6), and one O(8) atom to form PO4 tetrahedra that share corners with two equivalent Nb(1)O6 octahedra, corners with two equivalent Nb(2)O6 octahedra, and  a cornercorner with one Mg(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 31-52°. There are fourteen inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to two equivalent K(1) and one C(2) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one K(1), one Nb(1), and one C(1) atom. In the third O site, O(3) is bonded in a distorted T-shaped geometry to one Mg(1), one Nb(1), and one C(1) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one K(1), one Nb(1), and one P(1) atom. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to one Mg(1), one Nb(1), and one P(1) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one Mg(1), one Nb(1), and one P(2) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to one Mg(1), one Nb(2), and one P(1) atom. In the eighth O site, O(8) is bonded in a 3-coordinate geometry to one K(2), one Nb(1), and one P(2) atom. In the ninth O site, O(9) is bonded in a bent 150 degrees geometry to one Nb(2) and one P(1) atom. In the tenth O site, O(10) is bonded in a 3-coordinate geometry to one K(2), one Nb(2), and one P(2) atom. In the eleventh O site, O(11) is bonded in a distorted bent 150 degrees geometry to one Nb(2) and one P(2) atom. In the twelfth O site, O(12) is bonded in a 3-coordinate geometry to one K(2), one Nb(2), and one C(2) atom. In the thirteenth O site, O(13) is bonded in a 4-coordinate geometry to one K(1), one K(2), one Nb(2), and one C(2) atom. In the fourteenth O site, O(14) is bonded in a distorted single-bond geometry to one K(1), one K(2), and one C(1) atom.
K2MgNb2P2(CO7)2 crystallizes in the triclinic P1 space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 6-coordinate geometry to one O(13), one O(14), one O(2), one O(4), and two equivalent O(1) atoms. The K(1)-O(13) bond length is 2.69 Å. The K(1)-O(14) bond length is 2.95 Å. The K(1)-O(2) bond length is 2.85 Å. The K(1)-O(4) bond length is 2.97 Å. There is one shorter (2.67 Å) and one longer (2.92 Å) K(1)-O(1) bond length. In the second K site, K(2) is bonded in a 5-coordinate geometry to one O(10), one O(12), one O(13), one O(14), and one O(8) atom. The K(2)-O(10) bond length is 2.74 Å. The K(2)-O(12) bond length is 2.78 Å. The K(2)-O(13) bond length is 2.99 Å. The K(2)-O(14) bond length is 2.77 Å. The K(2)-O(8) bond length is 3.08 Å. Mg(1) is bonded to one O(3), one O(5), one O(6), and one O(7) atom to form MgO4 tetrahedra that share  a cornercorner with one Nb(1)O6 octahedra,  a cornercorner with one Nb(2)O6 octahedra,  a cornercorner with one P(2)O4 tetrahedra, corners with two equivalent P(1)O4 tetrahedra, and  an edgeedge with one Nb(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 71-77°. The Mg(1)-O(3) bond length is 1.95 Å. The Mg(1)-O(5) bond length is 1.99 Å. The Mg(1)-O(6) bond length is 2.01 Å. The Mg(1)-O(7) bond length is 1.98 Å. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(2), one O(3), one O(4), one O(5), one O(6), and one O(8) atom to form distorted NbO6 octahedra that share  a cornercorner with one Mg(1)O4 tetrahedra, corners with two equivalent P(1)O4 tetrahedra, corners with two equivalent P(2)O4 tetrahedra, and  an edgeedge with one Mg(1)O4 tetrahedra. The Nb(1)-O(2) bond length is 2.20 Å. The Nb(1)-O(3) bond length is 2.18 Å. The Nb(1)-O(4) bond length is 2.09 Å. The Nb(1)-O(5) bond length is 2.29 Å. The Nb(1)-O(6) bond length is 2.20 Å. The Nb(1)-O(8) bond length is 2.21 Å. In the second Nb site, Nb(2) is bonded to one O(10), one O(11), one O(12), one O(13), one O(7), and one O(9) atom to form NbO6 octahedra that share  a cornercorner with one Mg(1)O4 tetrahedra, corners with two equivalent P(1)O4 tetrahedra, and corners with two equivalent P(2)O4 tetrahedra. The Nb(2)-O(10) bond length is 2.14 Å. The Nb(2)-O(11) bond length is 2.10 Å. The Nb(2)-O(12) bond length is 2.11 Å. The Nb(2)-O(13) bond length is 2.17 Å. The Nb(2)-O(7) bond length is 2.39 Å. The Nb(2)-O(9) bond length is 2.15 Å. There are two inequivalent C sites. In the first C site, C(1) is bonded in a trigonal planar geometry to one O(14), one O(2), and one O(3) atom. The C(1)-O(14) bond length is 1.24 Å. The C(1)-O(2) bond length is 1.31 Å. The C(1)-O(3) bond length is 1.37 Å. In the second C site, C(2) is bonded in a trigonal planar geometry to one O(1), one O(12), and one O(13) atom. The C(2)-O(1) bond length is 1.25 Å. The C(2)-O(12) bond length is 1.34 Å. The C(2)-O(13) bond length is 1.33 Å. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(4), one O(5), one O(7), and one O(9) atom to form PO4 tetrahedra that share corners with two equivalent Nb(1)O6 octahedra, corners with two equivalent Nb(2)O6 octahedra, and corners with two equivalent Mg(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 27-57°. The P(1)-O(4) bond length is 1.54 Å. The P(1)-O(5) bond length is 1.59 Å. The P(1)-O(7) bond length is 1.57 Å. The P(1)-O(9) bond length is 1.52 Å. In the second P site, P(2) is bonded to one O(10), one O(11), one O(6), and one O(8) atom to form PO4 tetrahedra that share corners with two equivalent Nb(1)O6 octahedra, corners with two equivalent Nb(2)O6 octahedra, and  a cornercorner with one Mg(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 31-52°. The P(2)-O(10) bond length is 1.54 Å. The P(2)-O(11) bond length is 1.55 Å. The P(2)-O(6) bond length is 1.58 Å. The P(2)-O(8) bond length is 1.54 Å. There are fourteen inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to two equivalent K(1) and one C(2) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one K(1), one Nb(1), and one C(1) atom. In the third O site, O(3) is bonded in a distorted T-shaped geometry to one Mg(1), one Nb(1), and one C(1) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one K(1), one Nb(1), and one P(1) atom. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to one Mg(1), one Nb(1), and one P(1) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one Mg(1), one Nb(1), and one P(2) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to one Mg(1), one Nb(2), and one P(1) atom. In the eighth O site, O(8) is bonded in a 3-coordinate geometry to one K(2), one Nb(1), and one P(2) atom. In the ninth O site, O(9) is bonded in a bent 150 degrees geometry to one Nb(2) and one P(1) atom. In the tenth O site, O(10) is bonded in a 3-coordinate geometry to one K(2), one Nb(2), and one P(2) atom. In the eleventh O site, O(11) is bonded in a distorted bent 150 degrees geometry to one Nb(2) and one P(2) atom. In the twelfth O site, O(12) is bonded in a 3-coordinate geometry to one K(2), one Nb(2), and one C(2) atom. In the thirteenth O site, O(13) is bonded in a 4-coordinate geometry to one K(1), one K(2), one Nb(2), and one C(2) atom. In the fourteenth O site, O(14) is bonded in a distorted single-bond geometry to one K(1), one K(2), and one C(1) atom.