Np(BH4)4 is Protactinium structured and crystallizes in the tetragonal P4_2/nmc space group. The structure is zero-dimensional and consists of two Np(BH4)4 clusters. Np(1) is bonded to four equivalent H(2) and eight equivalent H(3) atoms to form NpH12 cuboctahedra that share faces with four equivalent B(1)H4 tetrahedra. B(1) is bonded to one H(1), one H(2), and two equivalent H(3) atoms to form BH4 tetrahedra that share  a faceface with one Np(1)H12 cuboctahedra. There are three inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one B(1) atom. In the second H site, H(2) is bonded in a distorted single-bond geometry to one Np(1) and one B(1) atom. In the third H site, H(3) is bonded in a distorted single-bond geometry to one Np(1) and one B(1) atom.
Np(BH4)4 is Protactinium structured and crystallizes in the tetragonal P4_2/nmc space group. The structure is zero-dimensional and consists of two Np(BH4)4 clusters. Np(1) is bonded to four equivalent H(2) and eight equivalent H(3) atoms to form NpH12 cuboctahedra that share faces with four equivalent B(1)H4 tetrahedra. All Np(1)-H(2) bond lengths are 2.24 Å. All Np(1)-H(3) bond lengths are 2.25 Å. B(1) is bonded to one H(1), one H(2), and two equivalent H(3) atoms to form BH4 tetrahedra that share  a faceface with one Np(1)H12 cuboctahedra. The B(1)-H(1) bond length is 1.19 Å. The B(1)-H(2) bond length is 1.25 Å. Both B(1)-H(3) bond lengths are 1.25 Å. There are three inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one B(1) atom. In the second H site, H(2) is bonded in a distorted single-bond geometry to one Np(1) and one B(1) atom. In the third H site, H(3) is bonded in a distorted single-bond geometry to one Np(1) and one B(1) atom.