KY(BH4)4 crystallizes in the orthorhombic Cmcm space group. K(1) is bonded to two equivalent H(3) and four equivalent H(5) atoms to form distorted KH6 octahedra that share corners with two equivalent B(1)H4 tetrahedra, corners with four equivalent B(2)H4 tetrahedra, and edges with two equivalent K(1)H6 octahedra. Y(1) is bonded to two equivalent H(4), two equivalent H(6), four equivalent H(1), and four equivalent H(2) atoms to form distorted YH12 cuboctahedra that share faces with two equivalent B(1)H4 tetrahedra and faces with two equivalent B(2)H4 tetrahedra. There are two inequivalent B sites. In the first B site, B(1) is bonded to one H(3), one H(4), and two equivalent H(1) atoms to form BH4 tetrahedra that share  a cornercorner with one K(1)H6 octahedra and  a faceface with one Y(1)H12 cuboctahedra. The corner-sharing octahedral tilt angles are 66°. In the second B site, B(2) is bonded to one H(5), one H(6), and two equivalent H(2) atoms to form BH4 tetrahedra that share corners with two equivalent K(1)H6 octahedra and  a faceface with one Y(1)H12 cuboctahedra. The corner-sharing octahedral tilt angles are 72°. There are six inequivalent H sites. In the first H site, H(2) is bonded in a distorted single-bond geometry to one Y(1) and one B(2) atom. In the second H site, H(3) is bonded in a distorted single-bond geometry to one K(1) and one B(1) atom. In the third H site, H(4) is bonded in a distorted single-bond geometry to one Y(1) and one B(1) atom. In the fourth H site, H(5) is bonded in a single-bond geometry to two equivalent K(1) and one B(2) atom. In the fifth H site, H(6) is bonded in a single-bond geometry to one Y(1) and one B(2) atom. In the sixth H site, H(1) is bonded in a distorted single-bond geometry to one Y(1) and one B(1) atom.
KY(BH4)4 crystallizes in the orthorhombic Cmcm space group. K(1) is bonded to two equivalent H(3) and four equivalent H(5) atoms to form distorted KH6 octahedra that share corners with two equivalent B(1)H4 tetrahedra, corners with four equivalent B(2)H4 tetrahedra, and edges with two equivalent K(1)H6 octahedra. Both K(1)-H(3) bond lengths are 2.74 Å. All K(1)-H(5) bond lengths are 2.90 Å. Y(1) is bonded to two equivalent H(4), two equivalent H(6), four equivalent H(1), and four equivalent H(2) atoms to form distorted YH12 cuboctahedra that share faces with two equivalent B(1)H4 tetrahedra and faces with two equivalent B(2)H4 tetrahedra. Both Y(1)-H(4) bond lengths are 2.34 Å. Both Y(1)-H(6) bond lengths are 2.37 Å. All Y(1)-H(1) bond lengths are 2.29 Å. All Y(1)-H(2) bond lengths are 2.33 Å. There are two inequivalent B sites. In the first B site, B(1) is bonded to one H(3), one H(4), and two equivalent H(1) atoms to form BH4 tetrahedra that share  a cornercorner with one K(1)H6 octahedra and  a faceface with one Y(1)H12 cuboctahedra. The corner-sharing octahedral tilt angles are 66°. The B(1)-H(3) bond length is 1.20 Å. The B(1)-H(4) bond length is 1.24 Å. Both B(1)-H(1) bond lengths are 1.24 Å. In the second B site, B(2) is bonded to one H(5), one H(6), and two equivalent H(2) atoms to form BH4 tetrahedra that share corners with two equivalent K(1)H6 octahedra and  a faceface with one Y(1)H12 cuboctahedra. The corner-sharing octahedral tilt angles are 72°. The B(2)-H(5) bond length is 1.21 Å. The B(2)-H(6) bond length is 1.24 Å. Both B(2)-H(2) bond lengths are 1.24 Å. There are six inequivalent H sites. In the first H site, H(2) is bonded in a distorted single-bond geometry to one Y(1) and one B(2) atom. In the second H site, H(3) is bonded in a distorted single-bond geometry to one K(1) and one B(1) atom. In the third H site, H(4) is bonded in a distorted single-bond geometry to one Y(1) and one B(1) atom. In the fourth H site, H(5) is bonded in a single-bond geometry to two equivalent K(1) and one B(2) atom. In the fifth H site, H(6) is bonded in a single-bond geometry to one Y(1) and one B(2) atom. In the sixth H site, H(1) is bonded in a distorted single-bond geometry to one Y(1) and one B(1) atom.