Pb2Mn2Si2O9 crystallizes in the orthorhombic C222_1 space group. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded in a distorted rectangular see-saw-like geometry to two equivalent O(2) and two equivalent O(4) atoms. In the second Mn site, Mn(2) is bonded in a 6-coordinate geometry to two equivalent O(3), two equivalent O(4), and two equivalent O(5) atoms. Pb(1) is bonded in a 4-coordinate geometry to one O(2), one O(5), and two equivalent O(4) atoms. Si(1) is bonded to one O(1), one O(2), one O(3), and one O(5) atom to form corner-sharing SiO4 tetrahedra. There are five inequivalent O sites. In the first O site, O(1) is bonded in a bent 120 degrees geometry to two equivalent Si(1) atoms. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Mn(1), one Pb(1), and one Si(1) atom. In the third O site, O(3) is bonded in a distorted bent 120 degrees geometry to one Mn(2) and one Si(1) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Mn(1), one Mn(2), and two equivalent Pb(1) atoms. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to one Mn(2), one Pb(1), and one Si(1) atom.
Pb2Mn2Si2O9 crystallizes in the orthorhombic C222_1 space group. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded in a distorted rectangular see-saw-like geometry to two equivalent O(2) and two equivalent O(4) atoms. Both Mn(1)-O(2) bond lengths are 2.02 Å. Both Mn(1)-O(4) bond lengths are 1.87 Å. In the second Mn site, Mn(2) is bonded in a 6-coordinate geometry to two equivalent O(3), two equivalent O(4), and two equivalent O(5) atoms. Both Mn(2)-O(3) bond lengths are 1.93 Å. Both Mn(2)-O(4) bond lengths are 2.53 Å. Both Mn(2)-O(5) bond lengths are 1.98 Å. Pb(1) is bonded in a 4-coordinate geometry to one O(2), one O(5), and two equivalent O(4) atoms. The Pb(1)-O(2) bond length is 2.45 Å. The Pb(1)-O(5) bond length is 2.48 Å. There is one shorter (2.38 Å) and one longer (2.48 Å) Pb(1)-O(4) bond length. Si(1) is bonded to one O(1), one O(2), one O(3), and one O(5) atom to form corner-sharing SiO4 tetrahedra. The Si(1)-O(1) bond length is 1.67 Å. The Si(1)-O(2) bond length is 1.66 Å. The Si(1)-O(3) bond length is 1.63 Å. The Si(1)-O(5) bond length is 1.64 Å. There are five inequivalent O sites. In the first O site, O(1) is bonded in a bent 120 degrees geometry to two equivalent Si(1) atoms. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Mn(1), one Pb(1), and one Si(1) atom. In the third O site, O(3) is bonded in a distorted bent 120 degrees geometry to one Mn(2) and one Si(1) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Mn(1), one Mn(2), and two equivalent Pb(1) atoms. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to one Mn(2), one Pb(1), and one Si(1) atom.