MgCr4(PbO4)4 crystallizes in the triclinic P1 space group. Mg(1) is bonded to one O(1), one O(11), one O(13), one O(6), and one O(9) atom to form distorted MgO5 trigonal bipyramids that share  a cornercorner with one Cr(1)O4 tetrahedra,  an edgeedge with one Cr(2)O4 tetrahedra, and  an edgeedge with one Cr(3)O4 tetrahedra. There are four inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to one O(1), one O(12), one O(16), and one O(5) atom to form CrO4 tetrahedra that share  a cornercorner with one Mg(1)O5 trigonal bipyramid. In the second Cr site, Cr(2) is bonded to one O(13), one O(4), one O(8), and one O(9) atom to form CrO4 tetrahedra that share  an edgeedge with one Mg(1)O5 trigonal bipyramid. In the third Cr site, Cr(3) is bonded to one O(11), one O(15), one O(2), and one O(6) atom to form CrO4 tetrahedra that share  an edgeedge with one Mg(1)O5 trigonal bipyramid. In the fourth Cr site, Cr(4) is bonded in a tetrahedral geometry to one O(10), one O(14), one O(3), and one O(7) atom. There are four inequivalent Pb sites. In the first Pb site, Pb(1) is bonded in a 6-coordinate geometry to one O(11), one O(12), one O(15), one O(4), one O(5), and one O(7) atom. In the second Pb site, Pb(2) is bonded in a 6-coordinate geometry to one O(11), one O(12), one O(16), one O(3), one O(6), and one O(8) atom. In the third Pb site, Pb(3) is bonded in a 3-coordinate geometry to one O(2), one O(7), and one O(9) atom. In the fourth Pb site, Pb(4) is bonded in a 5-coordinate geometry to one O(10), one O(14), one O(16), one O(4), and one O(8) atom. There are sixteen inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 150 degrees geometry to one Mg(1) and one Cr(1) atom. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to one Cr(3) and one Pb(3) atom. In the third O site, O(3) is bonded in a distorted single-bond geometry to one Cr(4) and one Pb(2) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Cr(2), one Pb(1), and one Pb(4) atom. In the fifth O site, O(5) is bonded in a distorted single-bond geometry to one Cr(1) and one Pb(1) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one Mg(1), one Cr(3), and one Pb(2) atom. In the seventh O site, O(7) is bonded in a distorted single-bond geometry to one Cr(4), one Pb(1), and one Pb(3) atom. In the eighth O site, O(8) is bonded in a distorted single-bond geometry to one Cr(2), one Pb(2), and one Pb(4) atom. In the ninth O site, O(9) is bonded in a 3-coordinate geometry to one Mg(1), one Cr(2), and one Pb(3) atom. In the tenth O site, O(10) is bonded in a distorted single-bond geometry to one Cr(4) and one Pb(4) atom. In the eleventh O site, O(11) is bonded in a distorted L-shaped geometry to one Mg(1), one Cr(3), one Pb(1), and one Pb(2) atom. In the twelfth O site, O(12) is bonded in a single-bond geometry to one Cr(1), one Pb(1), and one Pb(2) atom. In the thirteenth O site, O(13) is bonded in an L-shaped geometry to one Mg(1) and one Cr(2) atom. In the fourteenth O site, O(14) is bonded in a distorted bent 150 degrees geometry to one Cr(4) and one Pb(4) atom. In the fifteenth O site, O(15) is bonded in a distorted single-bond geometry to one Cr(3) and one Pb(1) atom. In the sixteenth O site, O(16) is bonded in a distorted single-bond geometry to one Cr(1), one Pb(2), and one Pb(4) atom.
MgCr4(PbO4)4 crystallizes in the triclinic P1 space group. Mg(1) is bonded to one O(1), one O(11), one O(13), one O(6), and one O(9) atom to form distorted MgO5 trigonal bipyramids that share  a cornercorner with one Cr(1)O4 tetrahedra,  an edgeedge with one Cr(2)O4 tetrahedra, and  an edgeedge with one Cr(3)O4 tetrahedra. The Mg(1)-O(1) bond length is 2.01 Å. The Mg(1)-O(11) bond length is 2.02 Å. The Mg(1)-O(13) bond length is 2.14 Å. The Mg(1)-O(6) bond length is 2.03 Å. The Mg(1)-O(9) bond length is 2.11 Å. There are four inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to one O(1), one O(12), one O(16), and one O(5) atom to form CrO4 tetrahedra that share  a cornercorner with one Mg(1)O5 trigonal bipyramid. The Cr(1)-O(1) bond length is 1.66 Å. The Cr(1)-O(12) bond length is 1.66 Å. The Cr(1)-O(16) bond length is 1.69 Å. The Cr(1)-O(5) bond length is 1.67 Å. In the second Cr site, Cr(2) is bonded to one O(13), one O(4), one O(8), and one O(9) atom to form CrO4 tetrahedra that share  an edgeedge with one Mg(1)O5 trigonal bipyramid. The Cr(2)-O(13) bond length is 1.69 Å. The Cr(2)-O(4) bond length is 1.73 Å. The Cr(2)-O(8) bond length is 1.74 Å. The Cr(2)-O(9) bond length is 1.76 Å. In the third Cr site, Cr(3) is bonded to one O(11), one O(15), one O(2), and one O(6) atom to form CrO4 tetrahedra that share  an edgeedge with one Mg(1)O5 trigonal bipyramid. The Cr(3)-O(11) bond length is 1.78 Å. The Cr(3)-O(15) bond length is 1.68 Å. The Cr(3)-O(2) bond length is 1.69 Å. The Cr(3)-O(6) bond length is 1.80 Å. In the fourth Cr site, Cr(4) is bonded in a tetrahedral geometry to one O(10), one O(14), one O(3), and one O(7) atom. The Cr(4)-O(10) bond length is 1.66 Å. The Cr(4)-O(14) bond length is 1.67 Å. The Cr(4)-O(3) bond length is 1.66 Å. The Cr(4)-O(7) bond length is 1.69 Å. There are four inequivalent Pb sites. In the first Pb site, Pb(1) is bonded in a 6-coordinate geometry to one O(11), one O(12), one O(15), one O(4), one O(5), and one O(7) atom. The Pb(1)-O(11) bond length is 2.81 Å. The Pb(1)-O(12) bond length is 2.72 Å. The Pb(1)-O(15) bond length is 2.46 Å. The Pb(1)-O(4) bond length is 2.58 Å. The Pb(1)-O(5) bond length is 2.57 Å. The Pb(1)-O(7) bond length is 2.49 Å. In the second Pb site, Pb(2) is bonded in a 6-coordinate geometry to one O(11), one O(12), one O(16), one O(3), one O(6), and one O(8) atom. The Pb(2)-O(11) bond length is 2.75 Å. The Pb(2)-O(12) bond length is 2.87 Å. The Pb(2)-O(16) bond length is 2.75 Å. The Pb(2)-O(3) bond length is 2.52 Å. The Pb(2)-O(6) bond length is 2.38 Å. The Pb(2)-O(8) bond length is 2.41 Å. In the third Pb site, Pb(3) is bonded in a 3-coordinate geometry to one O(2), one O(7), and one O(9) atom. The Pb(3)-O(2) bond length is 2.33 Å. The Pb(3)-O(7) bond length is 2.53 Å. The Pb(3)-O(9) bond length is 2.43 Å. In the fourth Pb site, Pb(4) is bonded in a 5-coordinate geometry to one O(10), one O(14), one O(16), one O(4), and one O(8) atom. The Pb(4)-O(10) bond length is 2.68 Å. The Pb(4)-O(14) bond length is 2.39 Å. The Pb(4)-O(16) bond length is 2.48 Å. The Pb(4)-O(4) bond length is 2.36 Å. The Pb(4)-O(8) bond length is 2.53 Å. There are sixteen inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 150 degrees geometry to one Mg(1) and one Cr(1) atom. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to one Cr(3) and one Pb(3) atom. In the third O site, O(3) is bonded in a distorted single-bond geometry to one Cr(4) and one Pb(2) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Cr(2), one Pb(1), and one Pb(4) atom. In the fifth O site, O(5) is bonded in a distorted single-bond geometry to one Cr(1) and one Pb(1) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one Mg(1), one Cr(3), and one Pb(2) atom. In the seventh O site, O(7) is bonded in a distorted single-bond geometry to one Cr(4), one Pb(1), and one Pb(3) atom. In the eighth O site, O(8) is bonded in a distorted single-bond geometry to one Cr(2), one Pb(2), and one Pb(4) atom. In the ninth O site, O(9) is bonded in a 3-coordinate geometry to one Mg(1), one Cr(2), and one Pb(3) atom. In the tenth O site, O(10) is bonded in a distorted single-bond geometry to one Cr(4) and one Pb(4) atom. In the eleventh O site, O(11) is bonded in a distorted L-shaped geometry to one Mg(1), one Cr(3), one Pb(1), and one Pb(2) atom. In the twelfth O site, O(12) is bonded in a single-bond geometry to one Cr(1), one Pb(1), and one Pb(2) atom. In the thirteenth O site, O(13) is bonded in an L-shaped geometry to one Mg(1) and one Cr(2) atom. In the fourteenth O site, O(14) is bonded in a distorted bent 150 degrees geometry to one Cr(4) and one Pb(4) atom. In the fifteenth O site, O(15) is bonded in a distorted single-bond geometry to one Cr(3) and one Pb(1) atom. In the sixteenth O site, O(16) is bonded in a distorted single-bond geometry to one Cr(1), one Pb(2), and one Pb(4) atom.