MgLa2(CuO3)2 crystallizes in the trigonal R3 space group. Mg(1) is bonded in a distorted trigonal planar geometry to three equivalent O(1) atoms. There are two inequivalent La sites. In the first La site, La(1) is bonded in a 6-coordinate geometry to three equivalent O(1) and three equivalent O(2) atoms. In the second La site, La(2) is bonded in a 6-coordinate geometry to three equivalent O(1) and three equivalent O(2) atoms. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in an octahedral geometry to three equivalent O(1) and three equivalent O(2) atoms. In the second Cu site, Cu(2) is bonded in a distorted trigonal planar geometry to three equivalent O(2) atoms. There are two inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), one La(1), one La(2), and one Cu(1) atom to form distorted OLa2MgCu trigonal pyramids that share corners with four equivalent O(1)La2MgCu trigonal pyramids, corners with seven equivalent O(2)La2Cu2 trigonal pyramids,  an edgeedge with one O(2)La2Cu2 trigonal pyramid, and edges with two equivalent O(1)La2MgCu trigonal pyramids. In the second O site, O(2) is bonded to one La(1), one La(2), one Cu(1), and one Cu(2) atom to form distorted OLa2Cu2 trigonal pyramids that share corners with four equivalent O(2)La2Cu2 trigonal pyramids, corners with seven equivalent O(1)La2MgCu trigonal pyramids,  an edgeedge with one O(1)La2MgCu trigonal pyramid, and edges with two equivalent O(2)La2Cu2 trigonal pyramids.
MgLa2(CuO3)2 crystallizes in the trigonal R3 space group. Mg(1) is bonded in a distorted trigonal planar geometry to three equivalent O(1) atoms. All Mg(1)-O(1) bond lengths are 1.93 Å. There are two inequivalent La sites. In the first La site, La(1) is bonded in a 6-coordinate geometry to three equivalent O(1) and three equivalent O(2) atoms. All La(1)-O(1) bond lengths are 2.36 Å. All La(1)-O(2) bond lengths are 2.56 Å. In the second La site, La(2) is bonded in a 6-coordinate geometry to three equivalent O(1) and three equivalent O(2) atoms. All La(2)-O(1) bond lengths are 2.50 Å. All La(2)-O(2) bond lengths are 2.40 Å. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in an octahedral geometry to three equivalent O(1) and three equivalent O(2) atoms. All Cu(1)-O(1) bond lengths are 2.14 Å. All Cu(1)-O(2) bond lengths are 2.10 Å. In the second Cu site, Cu(2) is bonded in a distorted trigonal planar geometry to three equivalent O(2) atoms. All Cu(2)-O(2) bond lengths are 1.92 Å. There are two inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), one La(1), one La(2), and one Cu(1) atom to form distorted OLa2MgCu trigonal pyramids that share corners with four equivalent O(1)La2MgCu trigonal pyramids, corners with seven equivalent O(2)La2Cu2 trigonal pyramids,  an edgeedge with one O(2)La2Cu2 trigonal pyramid, and edges with two equivalent O(1)La2MgCu trigonal pyramids. In the second O site, O(2) is bonded to one La(1), one La(2), one Cu(1), and one Cu(2) atom to form distorted OLa2Cu2 trigonal pyramids that share corners with four equivalent O(2)La2Cu2 trigonal pyramids, corners with seven equivalent O(1)La2MgCu trigonal pyramids,  an edgeedge with one O(1)La2MgCu trigonal pyramid, and edges with two equivalent O(2)La2Cu2 trigonal pyramids.