La2Ni9AlH2 crystallizes in the triclinic P1 space group. There are two inequivalent La sites. In the first La site, La(1) is bonded in a distorted single-bond geometry to two equivalent Ni(7), three equivalent Ni(1), three equivalent Ni(4), and one H(1) atom. In the second La site, La(2) is bonded in a 2-coordinate geometry to two equivalent Ni(7), three equivalent Ni(2), one H(1), and one H(2) atom. There are nine inequivalent Ni sites. In the first Ni site, Ni(1) is bonded in a 9-coordinate geometry to three equivalent La(1), one Ni(3), one Ni(5), one Ni(6), one Ni(7), one Ni(9), three equivalent Ni(4), and one Al(1) atom. In the second Ni site, Ni(2) is bonded in a 9-coordinate geometry to three equivalent La(2), one Ni(3), one Ni(5), one Ni(6), one Ni(7), one Ni(9), and one Al(1) atom. In the third Ni site, Ni(3) is bonded in a single-bond geometry to one Ni(1), one Ni(2), one Ni(4), two equivalent Ni(7), and one H(1) atom. In the fourth Ni site, Ni(4) is bonded in a 12-coordinate geometry to three equivalent La(1), one Ni(3), one Ni(5), one Ni(6), one Ni(7), one Ni(9), three equivalent Ni(1), and one Al(1) atom. In the fifth Ni site, Ni(5) is bonded in a distorted single-bond geometry to one Ni(1), one Ni(2), one Ni(4), two equivalent Al(1), and one H(2) atom. In the sixth Ni site, Ni(6) is bonded in a single-bond geometry to one Ni(1), one Ni(2), one Ni(4), two equivalent Ni(7), and one H(1) atom. In the seventh Ni site, Ni(7) is bonded to two equivalent La(1), two equivalent La(2), one Ni(1), one Ni(2), one Ni(4), one Ni(8), two equivalent Ni(3), and two equivalent Ni(6) atoms to form NiLa4Ni8 cuboctahedra that share corners with four equivalent Ni(7)La4Ni8 cuboctahedra,  a cornercorner with one H(2)LaNi3 tetrahedra, edges with two equivalent Ni(7)La4Ni8 cuboctahedra,  an edgeedge with one H(1)La2Ni2 tetrahedra,  an edgeedge with one H(2)LaNi3 tetrahedra, and faces with two equivalent H(1)La2Ni2 tetrahedra. In the eighth Ni site, Ni(8) is bonded in a distorted single-bond geometry to one Ni(7), one Al(1), and one H(2) atom. In the ninth Ni site, Ni(9) is bonded in a distorted single-bond geometry to one Ni(1), one Ni(2), one Ni(4), two equivalent Al(1), and one H(2) atom. Al(1) is bonded in a 8-coordinate geometry to one Ni(1), one Ni(2), one Ni(4), one Ni(8), two equivalent Ni(5), and two equivalent Ni(9) atoms. There are two inequivalent H sites. In the first H site, H(1) is bonded to one La(1), one La(2), one Ni(3), and one Ni(6) atom to form HLa2Ni2 tetrahedra that share  a cornercorner with one H(2)LaNi3 tetrahedra,  an edgeedge with one Ni(7)La4Ni8 cuboctahedra, and faces with two equivalent Ni(7)La4Ni8 cuboctahedra. In the second H site, H(2) is bonded to one La(2), one Ni(5), one Ni(8), and one Ni(9) atom to form distorted HLaNi3 tetrahedra that share  a cornercorner with one Ni(7)La4Ni8 cuboctahedra,  a cornercorner with one H(1)La2Ni2 tetrahedra, and  an edgeedge with one Ni(7)La4Ni8 cuboctahedra.
La2Ni9AlH2 crystallizes in the triclinic P1 space group. There are two inequivalent La sites. In the first La site, La(1) is bonded in a distorted single-bond geometry to two equivalent Ni(7), three equivalent Ni(1), three equivalent Ni(4), and one H(1) atom. There is one shorter (3.19 Å) and one longer (3.20 Å) La(1)-Ni(7) bond length. There are a spread of La(1)-Ni(1) bond distances ranging from 2.90-2.96 Å. There are a spread of La(1)-Ni(4) bond distances ranging from 2.87-2.99 Å. The La(1)-H(1) bond length is 2.38 Å. In the second La site, La(2) is bonded in a 2-coordinate geometry to two equivalent Ni(7), three equivalent Ni(2), one H(1), and one H(2) atom. There is one shorter (3.16 Å) and one longer (3.17 Å) La(2)-Ni(7) bond length. There are a spread of La(2)-Ni(2) bond distances ranging from 2.89-2.96 Å. The La(2)-H(1) bond length is 2.36 Å. The La(2)-H(2) bond length is 2.35 Å. There are nine inequivalent Ni sites. In the first Ni site, Ni(1) is bonded in a 9-coordinate geometry to three equivalent La(1), one Ni(3), one Ni(5), one Ni(6), one Ni(7), one Ni(9), three equivalent Ni(4), and one Al(1) atom. The Ni(1)-Ni(3) bond length is 2.46 Å. The Ni(1)-Ni(5) bond length is 2.44 Å. The Ni(1)-Ni(6) bond length is 2.50 Å. The Ni(1)-Ni(7) bond length is 2.50 Å. The Ni(1)-Ni(9) bond length is 2.46 Å. There are a spread of Ni(1)-Ni(4) bond distances ranging from 2.90-2.98 Å. The Ni(1)-Al(1) bond length is 2.50 Å. In the second Ni site, Ni(2) is bonded in a 9-coordinate geometry to three equivalent La(2), one Ni(3), one Ni(5), one Ni(6), one Ni(7), one Ni(9), and one Al(1) atom. The Ni(2)-Ni(3) bond length is 2.49 Å. The Ni(2)-Ni(5) bond length is 2.53 Å. The Ni(2)-Ni(6) bond length is 2.50 Å. The Ni(2)-Ni(7) bond length is 2.50 Å. The Ni(2)-Ni(9) bond length is 2.55 Å. The Ni(2)-Al(1) bond length is 2.44 Å. In the third Ni site, Ni(3) is bonded in a single-bond geometry to one Ni(1), one Ni(2), one Ni(4), two equivalent Ni(7), and one H(1) atom. The Ni(3)-Ni(4) bond length is 2.51 Å. There is one shorter (2.51 Å) and one longer (2.52 Å) Ni(3)-Ni(7) bond length. The Ni(3)-H(1) bond length is 1.58 Å. In the fourth Ni site, Ni(4) is bonded in a 12-coordinate geometry to three equivalent La(1), one Ni(3), one Ni(5), one Ni(6), one Ni(7), one Ni(9), three equivalent Ni(1), and one Al(1) atom. The Ni(4)-Ni(5) bond length is 2.50 Å. The Ni(4)-Ni(6) bond length is 2.54 Å. The Ni(4)-Ni(7) bond length is 2.48 Å. The Ni(4)-Ni(9) bond length is 2.54 Å. The Ni(4)-Al(1) bond length is 2.46 Å. In the fifth Ni site, Ni(5) is bonded in a distorted single-bond geometry to one Ni(1), one Ni(2), one Ni(4), two equivalent Al(1), and one H(2) atom. There is one shorter (2.51 Å) and one longer (2.52 Å) Ni(5)-Al(1) bond length. The Ni(5)-H(2) bond length is 1.62 Å. In the sixth Ni site, Ni(6) is bonded in a single-bond geometry to one Ni(1), one Ni(2), one Ni(4), two equivalent Ni(7), and one H(1) atom. There is one shorter (2.56 Å) and one longer (2.59 Å) Ni(6)-Ni(7) bond length. The Ni(6)-H(1) bond length is 1.57 Å. In the seventh Ni site, Ni(7) is bonded to two equivalent La(1), two equivalent La(2), one Ni(1), one Ni(2), one Ni(4), one Ni(8), two equivalent Ni(3), and two equivalent Ni(6) atoms to form NiLa4Ni8 cuboctahedra that share corners with four equivalent Ni(7)La4Ni8 cuboctahedra,  a cornercorner with one H(2)LaNi3 tetrahedra, edges with two equivalent Ni(7)La4Ni8 cuboctahedra,  an edgeedge with one H(1)La2Ni2 tetrahedra,  an edgeedge with one H(2)LaNi3 tetrahedra, and faces with two equivalent H(1)La2Ni2 tetrahedra. The Ni(7)-Ni(8) bond length is 2.51 Å. In the eighth Ni site, Ni(8) is bonded in a distorted single-bond geometry to one Ni(7), one Al(1), and one H(2) atom. The Ni(8)-Al(1) bond length is 2.53 Å. The Ni(8)-H(2) bond length is 1.66 Å. In the ninth Ni site, Ni(9) is bonded in a distorted single-bond geometry to one Ni(1), one Ni(2), one Ni(4), two equivalent Al(1), and one H(2) atom. There is one shorter (2.52 Å) and one longer (2.53 Å) Ni(9)-Al(1) bond length. The Ni(9)-H(2) bond length is 1.62 Å. Al(1) is bonded in a 8-coordinate geometry to one Ni(1), one Ni(2), one Ni(4), one Ni(8), two equivalent Ni(5), and two equivalent Ni(9) atoms. There are two inequivalent H sites. In the first H site, H(1) is bonded to one La(1), one La(2), one Ni(3), and one Ni(6) atom to form HLa2Ni2 tetrahedra that share  a cornercorner with one H(2)LaNi3 tetrahedra,  an edgeedge with one Ni(7)La4Ni8 cuboctahedra, and faces with two equivalent Ni(7)La4Ni8 cuboctahedra. In the second H site, H(2) is bonded to one La(2), one Ni(5), one Ni(8), and one Ni(9) atom to form distorted HLaNi3 tetrahedra that share  a cornercorner with one Ni(7)La4Ni8 cuboctahedra,  a cornercorner with one H(1)La2Ni2 tetrahedra, and  an edgeedge with one Ni(7)La4Ni8 cuboctahedra.