Cr3Mn2(CO2)18 crystallizes in the monoclinic C2/c space group. There are two inequivalent Cr sites. In the first Cr site, Cr(1) is bonded in an octahedral geometry to one O(10), one O(11), one O(12), one O(7), one O(8), and one O(9) atom. The Cr(1)-O(10) bond length is 1.98 Å. The Cr(1)-O(11) bond length is 1.97 Å. The Cr(1)-O(12) bond length is 1.96 Å. The Cr(1)-O(7) bond length is 1.97 Å. The Cr(1)-O(8) bond length is 1.97 Å. The Cr(1)-O(9) bond length is 1.98 Å. In the second Cr site, Cr(2) is bonded in an octahedral geometry to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms. Both Cr(2)-O(1) bond lengths are 1.98 Å. Both Cr(2)-O(3) bond lengths are 2.00 Å. Both Cr(2)-O(4) bond lengths are 1.97 Å. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded in a 8-coordinate geometry to two equivalent O(13), two equivalent O(14), two equivalent O(15), and two equivalent O(16) atoms. Both Mn(1)-O(13) bond lengths are 2.27 Å. Both Mn(1)-O(14) bond lengths are 2.49 Å. Both Mn(1)-O(15) bond lengths are 2.34 Å. Both Mn(1)-O(16) bond lengths are 2.27 Å. In the second Mn site, Mn(2) is bonded in a 8-coordinate geometry to two equivalent O(18), two equivalent O(2), two equivalent O(5), and two equivalent O(6) atoms. Both Mn(2)-O(18) bond lengths are 2.37 Å. Both Mn(2)-O(2) bond lengths are 2.27 Å. Both Mn(2)-O(5) bond lengths are 2.25 Å. Both Mn(2)-O(6) bond lengths are 2.42 Å. There are nine inequivalent C sites. In the first C site, C(1) is bonded in a distorted bent 120 degrees geometry to one O(1) and one O(2) atom. The C(1)-O(1) bond length is 1.29 Å. The C(1)-O(2) bond length is 1.23 Å. In the second C site, C(2) is bonded in a distorted bent 120 degrees geometry to one O(6) and one O(8) atom. The C(2)-O(6) bond length is 1.24 Å. The C(2)-O(8) bond length is 1.29 Å. In the third C site, C(3) is bonded in a distorted bent 120 degrees geometry to one O(5) and one O(7) atom. The C(3)-O(5) bond length is 1.23 Å. The C(3)-O(7) bond length is 1.28 Å. In the fourth C site, C(4) is bonded in a distorted bent 120 degrees geometry to one O(14) and one O(9) atom. The C(4)-O(14) bond length is 1.22 Å. The C(4)-O(9) bond length is 1.30 Å. In the fifth C site, C(5) is bonded in a distorted bent 120 degrees geometry to one O(10) and one O(13) atom. The C(5)-O(10) bond length is 1.30 Å. The C(5)-O(13) bond length is 1.23 Å. In the sixth C site, C(6) is bonded in a distorted bent 120 degrees geometry to one O(12) and one O(16) atom. The C(6)-O(12) bond length is 1.28 Å. The C(6)-O(16) bond length is 1.24 Å. In the seventh C site, C(7) is bonded in a distorted bent 120 degrees geometry to one O(11) and one O(17) atom. The C(7)-O(11) bond length is 1.28 Å. The C(7)-O(17) bond length is 1.23 Å. In the eighth C site, C(8) is bonded in a distorted bent 120 degrees geometry to one O(15) and one O(4) atom. The C(8)-O(15) bond length is 1.22 Å. The C(8)-O(4) bond length is 1.30 Å. In the ninth C site, C(9) is bonded in a distorted bent 120 degrees geometry to one O(18) and one O(3) atom. The C(9)-O(18) bond length is 1.21 Å. The C(9)-O(3) bond length is 1.28 Å. There are eighteen inequivalent O sites. In the first O site, O(1) is bonded in a bent 120 degrees geometry to one Cr(2) and one C(1) atom. In the second O site, O(2) is bonded in a bent 120 degrees geometry to one Mn(2) and one C(1) atom. In the third O site, O(3) is bonded in a bent 120 degrees geometry to one Cr(2) and one C(9) atom. In the fourth O site, O(4) is bonded in a bent 120 degrees geometry to one Cr(2) and one C(8) atom. In the fifth O site, O(5) is bonded in a bent 120 degrees geometry to one Mn(2) and one C(3) atom. In the sixth O site, O(6) is bonded in a distorted bent 120 degrees geometry to one Mn(2) and one C(2) atom. In the seventh O site, O(7) is bonded in a bent 120 degrees geometry to one Cr(1) and one C(3) atom. In the eighth O site, O(8) is bonded in a bent 120 degrees geometry to one Cr(1) and one C(2) atom. In the ninth O site, O(9) is bonded in a bent 120 degrees geometry to one Cr(1) and one C(4) atom. In the tenth O site, O(10) is bonded in a bent 120 degrees geometry to one Cr(1) and one C(5) atom. In the eleventh O site, O(11) is bonded in a bent 120 degrees geometry to one Cr(1) and one C(7) atom. In the twelfth O site, O(12) is bonded in a bent 120 degrees geometry to one Cr(1) and one C(6) atom. In the thirteenth O site, O(13) is bonded in a bent 120 degrees geometry to one Mn(1) and one C(5) atom. In the fourteenth O site, O(14) is bonded in a distorted single-bond geometry to one Mn(1) and one C(4) atom. In the fifteenth O site, O(15) is bonded in a bent 120 degrees geometry to one Mn(1) and one C(8) atom. In the sixteenth O site, O(16) is bonded in a bent 120 degrees geometry to one Mn(1) and one C(6) atom. In the seventeenth O site, O(17) is bonded in a single-bond geometry to one C(7) atom. In the eighteenth O site, O(18) is bonded in a bent 120 degrees geometry to one Mn(2) and one C(9) atom. Linkers: 36 [O]C(=O)C([O])=O. Metal clusters: 8 [Mn] ,12 [Cr]. The MOF has largest included sphere 4.62 A, density 1.38 g/cm3, surface area 3350.06 m2/g, accessible volume 0.30 cm3/g