FeH4(CN)8(C2NH2)2 crystallizes in the orthorhombic Pnma space group. The structure consists of four pyrimidine molecules inside a FeH4(CN)8 framework. In the FeH4(CN)8 framework, Fe(1) is bonded in an octahedral geometry to two equivalent N(1), two equivalent N(2), and two equivalent N(3) atoms. Both Fe(1)-N(1) bond lengths are 2.18 Å. Both Fe(1)-N(2) bond lengths are 2.10 Å. Both Fe(1)-N(3) bond lengths are 2.10 Å. There are five inequivalent C sites. In the first C site, C(1) is bonded in a trigonal planar geometry to two equivalent N(1) and one H(1) atom. Both C(1)-N(1) bond lengths are 1.34 Å. The C(1)-H(1) bond length is 1.09 Å. In the second C site, C(2) is bonded in a distorted trigonal planar geometry to one C(3), one N(1), and one H(2) atom. The C(2)-C(3) bond length is 1.39 Å. The C(2)-N(1) bond length is 1.35 Å. The C(2)-H(2) bond length is 1.09 Å. In the third C site, C(3) is bonded in a distorted single-bond geometry to two equivalent C(2) and one H(3) atom. The C(3)-H(3) bond length is 1.09 Å. In the fourth C site, C(4) is bonded in a linear geometry to one N(2) and one N(4) atom. The C(4)-N(2) bond length is 1.18 Å. The C(4)-N(4) bond length is 1.29 Å. In the fifth C site, C(5) is bonded in a linear geometry to one N(3) and one N(4) atom. The C(5)-N(3) bond length is 1.18 Å. The C(5)-N(4) bond length is 1.29 Å. There are four inequivalent N sites. In the first N site, N(3) is bonded in a bent 150 degrees geometry to one Fe(1) and one C(5) atom. In the second N site, N(4) is bonded in a bent 120 degrees geometry to one C(4) and one C(5) atom. In the third N site, N(2) is bonded in a linear geometry to one Fe(1) and one C(4) atom. In the fourth N site, N(1) is bonded in a trigonal planar geometry to one Fe(1), one C(1), and one C(2) atom. There are three inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one C(1) atom. In the second H site, H(2) is bonded in a single-bond geometry to one C(2) atom. In the third H site, H(3) is bonded in a single-bond geometry to one C(3) atom. Linkers: 4 c1cncnc1. Metal clusters: 4 [Fe]. The MOF has largest included sphere 2.01 A, density 1.58 g/cm3, surface area 4759.74 m2/g, accessible volume 0.16 cm3/g