Sr6Mg(W2O9)2 crystallizes in the triclinic P-1 space group. There are three inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 7-coordinate geometry to one O(1), one O(2), one O(4), one O(5), one O(7), one O(8), and one O(9) atom. In the second Sr site, Sr(2) is bonded in a 7-coordinate geometry to one O(1), one O(2), one O(5), one O(9), two equivalent O(4), and two equivalent O(6) atoms. In the third Sr site, Sr(3) is bonded in a 9-coordinate geometry to one O(1), one O(6), one O(8), two equivalent O(3), two equivalent O(7), and two equivalent O(9) atoms. Mg(1) is bonded in a square co-planar geometry to two equivalent O(3) and two equivalent O(8) atoms. There are two inequivalent W sites. In the first W site, W(1) is bonded to one O(1), one O(2), one O(3), one O(5), one O(6), and one O(9) atom to form distorted face-sharing WO6 octahedra. In the second W site, W(2) is bonded to one O(3), one O(4), one O(5), one O(6), one O(7), and one O(8) atom to form distorted face-sharing WO6 pentagonal pyramids. There are nine inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Sr(1), one Sr(2), one Sr(3), and one W(1) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Sr(1), one Sr(2), and one W(1) atom. In the third O site, O(3) is bonded to two equivalent Sr(3), one Mg(1), one W(1), and one W(2) atom to form distorted OSr2MgW2 trigonal bipyramids that share corners with three equivalent O(7)Sr3W tetrahedra,  a cornercorner with one O(3)Sr2MgW2 trigonal bipyramid,  a cornercorner with one O(8)Sr2MgW trigonal pyramid,  an edgeedge with one O(7)Sr3W tetrahedra,  an edgeedge with one O(3)Sr2MgW2 trigonal bipyramid, and edges with two equivalent O(8)Sr2MgW trigonal pyramids. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Sr(1), two equivalent Sr(2), and one W(2) atom. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to one Sr(1), one Sr(2), one W(1), and one W(2) atom. In the sixth O site, O(6) is bonded in a 5-coordinate geometry to one Sr(3), two equivalent Sr(2), one W(1), and one W(2) atom. In the seventh O site, O(7) is bonded to one Sr(1), two equivalent Sr(3), and one W(2) atom to form distorted OSr3W tetrahedra that share corners with three equivalent O(3)Sr2MgW2 trigonal bipyramids, corners with two equivalent O(8)Sr2MgW trigonal pyramids,  an edgeedge with one O(7)Sr3W tetrahedra,  an edgeedge with one O(3)Sr2MgW2 trigonal bipyramid, and  an edgeedge with one O(8)Sr2MgW trigonal pyramid. In the eighth O site, O(8) is bonded to one Sr(1), one Sr(3), one Mg(1), and one W(2) atom to form distorted OSr2MgW trigonal pyramids that share corners with two equivalent O(7)Sr3W tetrahedra,  a cornercorner with one O(3)Sr2MgW2 trigonal bipyramid,  a cornercorner with one O(8)Sr2MgW trigonal pyramid,  an edgeedge with one O(7)Sr3W tetrahedra, and edges with two equivalent O(3)Sr2MgW2 trigonal bipyramids. In the ninth O site, O(9) is bonded in a 1-coordinate geometry to one Sr(1), one Sr(2), two equivalent Sr(3), and one W(1) atom.
Sr6Mg(W2O9)2 crystallizes in the triclinic P-1 space group. There are three inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 7-coordinate geometry to one O(1), one O(2), one O(4), one O(5), one O(7), one O(8), and one O(9) atom. The Sr(1)-O(1) bond length is 2.70 Å. The Sr(1)-O(2) bond length is 2.44 Å. The Sr(1)-O(4) bond length is 2.46 Å. The Sr(1)-O(5) bond length is 3.05 Å. The Sr(1)-O(7) bond length is 2.67 Å. The Sr(1)-O(8) bond length is 2.51 Å. The Sr(1)-O(9) bond length is 2.79 Å. In the second Sr site, Sr(2) is bonded in a 7-coordinate geometry to one O(1), one O(2), one O(5), one O(9), two equivalent O(4), and two equivalent O(6) atoms. The Sr(2)-O(1) bond length is 2.70 Å. The Sr(2)-O(2) bond length is 2.64 Å. The Sr(2)-O(5) bond length is 2.59 Å. The Sr(2)-O(9) bond length is 2.76 Å. There is one shorter (2.65 Å) and one longer (2.89 Å) Sr(2)-O(4) bond length. There is one shorter (2.59 Å) and one longer (3.16 Å) Sr(2)-O(6) bond length. In the third Sr site, Sr(3) is bonded in a 9-coordinate geometry to one O(1), one O(6), one O(8), two equivalent O(3), two equivalent O(7), and two equivalent O(9) atoms. The Sr(3)-O(1) bond length is 3.32 Å. The Sr(3)-O(6) bond length is 2.65 Å. The Sr(3)-O(8) bond length is 2.41 Å. There is one shorter (2.63 Å) and one longer (2.76 Å) Sr(3)-O(3) bond length. There is one shorter (2.50 Å) and one longer (2.57 Å) Sr(3)-O(7) bond length. There is one shorter (2.96 Å) and one longer (3.24 Å) Sr(3)-O(9) bond length. Mg(1) is bonded in a square co-planar geometry to two equivalent O(3) and two equivalent O(8) atoms. Both Mg(1)-O(3) bond lengths are 2.10 Å. Both Mg(1)-O(8) bond lengths are 1.92 Å. There are two inequivalent W sites. In the first W site, W(1) is bonded to one O(1), one O(2), one O(3), one O(5), one O(6), and one O(9) atom to form distorted face-sharing WO6 octahedra. The W(1)-O(1) bond length is 1.86 Å. The W(1)-O(2) bond length is 1.85 Å. The W(1)-O(3) bond length is 2.13 Å. The W(1)-O(5) bond length is 2.04 Å. The W(1)-O(6) bond length is 2.20 Å. The W(1)-O(9) bond length is 1.88 Å. In the second W site, W(2) is bonded to one O(3), one O(4), one O(5), one O(6), one O(7), and one O(8) atom to form distorted face-sharing WO6 pentagonal pyramids. The W(2)-O(3) bond length is 2.17 Å. The W(2)-O(4) bond length is 1.88 Å. The W(2)-O(5) bond length is 2.21 Å. The W(2)-O(6) bond length is 2.06 Å. The W(2)-O(7) bond length is 1.93 Å. The W(2)-O(8) bond length is 2.00 Å. There are nine inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Sr(1), one Sr(2), one Sr(3), and one W(1) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Sr(1), one Sr(2), and one W(1) atom. In the third O site, O(3) is bonded to two equivalent Sr(3), one Mg(1), one W(1), and one W(2) atom to form distorted OSr2MgW2 trigonal bipyramids that share corners with three equivalent O(7)Sr3W tetrahedra,  a cornercorner with one O(3)Sr2MgW2 trigonal bipyramid,  a cornercorner with one O(8)Sr2MgW trigonal pyramid,  an edgeedge with one O(7)Sr3W tetrahedra,  an edgeedge with one O(3)Sr2MgW2 trigonal bipyramid, and edges with two equivalent O(8)Sr2MgW trigonal pyramids. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Sr(1), two equivalent Sr(2), and one W(2) atom. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to one Sr(1), one Sr(2), one W(1), and one W(2) atom. In the sixth O site, O(6) is bonded in a 5-coordinate geometry to one Sr(3), two equivalent Sr(2), one W(1), and one W(2) atom. In the seventh O site, O(7) is bonded to one Sr(1), two equivalent Sr(3), and one W(2) atom to form distorted OSr3W tetrahedra that share corners with three equivalent O(3)Sr2MgW2 trigonal bipyramids, corners with two equivalent O(8)Sr2MgW trigonal pyramids,  an edgeedge with one O(7)Sr3W tetrahedra,  an edgeedge with one O(3)Sr2MgW2 trigonal bipyramid, and  an edgeedge with one O(8)Sr2MgW trigonal pyramid. In the eighth O site, O(8) is bonded to one Sr(1), one Sr(3), one Mg(1), and one W(2) atom to form distorted OSr2MgW trigonal pyramids that share corners with two equivalent O(7)Sr3W tetrahedra,  a cornercorner with one O(3)Sr2MgW2 trigonal bipyramid,  a cornercorner with one O(8)Sr2MgW trigonal pyramid,  an edgeedge with one O(7)Sr3W tetrahedra, and edges with two equivalent O(3)Sr2MgW2 trigonal bipyramids. In the ninth O site, O(9) is bonded in a 1-coordinate geometry to one Sr(1), one Sr(2), two equivalent Sr(3), and one W(1) atom.