FePb2As2O9 crystallizes in the monoclinic P2_1/m space group. Fe(1) is bonded to two equivalent O(3), two equivalent O(4), and two equivalent O(7) atoms to form FeO6 octahedra that share corners with two equivalent As(1)O4 tetrahedra, corners with two equivalent As(2)O4 tetrahedra, and edges with two equivalent Fe(1)O6 octahedra. There are two inequivalent Pb sites. In the first Pb site, Pb(1) is bonded in a distorted rectangular see-saw-like geometry to one O(1), one O(2), and two equivalent O(6) atoms. In the second Pb site, Pb(2) is bonded in a 6-coordinate geometry to one O(4), one O(5), two equivalent O(6), and two equivalent O(7) atoms. There are two inequivalent As sites. In the first As site, As(1) is bonded to one O(1), one O(5), and two equivalent O(7) atoms to form AsO4 tetrahedra that share corners with two equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles are 56°. In the second As site, As(2) is bonded to one O(2), one O(3), and two equivalent O(6) atoms to form AsO4 tetrahedra that share corners with two equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles are 46°. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to one Pb(1) and one As(1) atom. In the second O site, O(2) is bonded in a distorted bent 120 degrees geometry to one Pb(1) and one As(2) atom. In the third O site, O(3) is bonded in a distorted T-shaped geometry to two equivalent Fe(1) and one As(2) atom. In the fourth O site, O(4) is bonded in a distorted water-like geometry to two equivalent Fe(1) and one Pb(2) atom. In the fifth O site, O(5) is bonded in a distorted linear geometry to one Pb(2) and one As(1) atom. In the sixth O site, O(6) is bonded in a distorted single-bond geometry to one Pb(1), one Pb(2), and one As(2) atom. In the seventh O site, O(7) is bonded in a bent 120 degrees geometry to one Fe(1), one Pb(2), and one As(1) atom.
FePb2As2O9 crystallizes in the monoclinic P2_1/m space group. Fe(1) is bonded to two equivalent O(3), two equivalent O(4), and two equivalent O(7) atoms to form FeO6 octahedra that share corners with two equivalent As(1)O4 tetrahedra, corners with two equivalent As(2)O4 tetrahedra, and edges with two equivalent Fe(1)O6 octahedra. Both Fe(1)-O(3) bond lengths are 2.09 Å. Both Fe(1)-O(4) bond lengths are 1.89 Å. Both Fe(1)-O(7) bond lengths are 2.01 Å. There are two inequivalent Pb sites. In the first Pb site, Pb(1) is bonded in a distorted rectangular see-saw-like geometry to one O(1), one O(2), and two equivalent O(6) atoms. The Pb(1)-O(1) bond length is 2.51 Å. The Pb(1)-O(2) bond length is 2.46 Å. Both Pb(1)-O(6) bond lengths are 2.45 Å. In the second Pb site, Pb(2) is bonded in a 6-coordinate geometry to one O(4), one O(5), two equivalent O(6), and two equivalent O(7) atoms. The Pb(2)-O(4) bond length is 2.59 Å. The Pb(2)-O(5) bond length is 2.59 Å. Both Pb(2)-O(6) bond lengths are 2.63 Å. Both Pb(2)-O(7) bond lengths are 2.81 Å. There are two inequivalent As sites. In the first As site, As(1) is bonded to one O(1), one O(5), and two equivalent O(7) atoms to form AsO4 tetrahedra that share corners with two equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles are 56°. The As(1)-O(1) bond length is 1.71 Å. The As(1)-O(5) bond length is 1.69 Å. Both As(1)-O(7) bond lengths are 1.76 Å. In the second As site, As(2) is bonded to one O(2), one O(3), and two equivalent O(6) atoms to form AsO4 tetrahedra that share corners with two equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles are 46°. The As(2)-O(2) bond length is 1.70 Å. The As(2)-O(3) bond length is 1.77 Å. Both As(2)-O(6) bond lengths are 1.73 Å. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to one Pb(1) and one As(1) atom. In the second O site, O(2) is bonded in a distorted bent 120 degrees geometry to one Pb(1) and one As(2) atom. In the third O site, O(3) is bonded in a distorted T-shaped geometry to two equivalent Fe(1) and one As(2) atom. In the fourth O site, O(4) is bonded in a distorted water-like geometry to two equivalent Fe(1) and one Pb(2) atom. In the fifth O site, O(5) is bonded in a distorted linear geometry to one Pb(2) and one As(1) atom. In the sixth O site, O(6) is bonded in a distorted single-bond geometry to one Pb(1), one Pb(2), and one As(2) atom. In the seventh O site, O(7) is bonded in a bent 120 degrees geometry to one Fe(1), one Pb(2), and one As(1) atom.