RbBa2Ni2F9 crystallizes in the trigonal R3m space group. Rb(1) is bonded to three equivalent F(1), three equivalent F(3), and six equivalent F(2) atoms to form distorted RbF12 cuboctahedra that share corners with six equivalent Rb(1)F12 cuboctahedra, corners with three equivalent Ni(1)F6 octahedra, faces with four equivalent Ba(1)F12 cuboctahedra,  a faceface with one Ni(1)F6 octahedra, and faces with three equivalent Ni(2)F6 octahedra. The corner-sharing octahedral tilt angles are 24°. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded to three equivalent F(1), three equivalent F(2), and six equivalent F(3) atoms to form BaF12 cuboctahedra that share corners with six equivalent Ba(1)F12 cuboctahedra, faces with four equivalent Rb(1)F12 cuboctahedra, faces with three equivalent Ni(1)F6 octahedra, and faces with three equivalent Ni(2)F6 octahedra. In the second Ba site, Ba(2) is bonded in a 12-coordinate geometry to three equivalent F(2), three equivalent F(3), and six equivalent F(1) atoms. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to three equivalent F(1) and three equivalent F(3) atoms to form NiF6 octahedra that share corners with three equivalent Rb(1)F12 cuboctahedra, corners with three equivalent Ni(2)F6 octahedra,  a faceface with one Rb(1)F12 cuboctahedra, and faces with three equivalent Ba(1)F12 cuboctahedra. The corner-sharing octahedral tilt angles are 5°. In the second Ni site, Ni(2) is bonded to three equivalent F(2) and three equivalent F(3) atoms to form NiF6 octahedra that share corners with three equivalent Ni(1)F6 octahedra, faces with three equivalent Rb(1)F12 cuboctahedra, and faces with three equivalent Ba(1)F12 cuboctahedra. The corner-sharing octahedral tilt angles are 5°. There are three inequivalent F sites. In the first F site, F(1) is bonded in a distorted single-bond geometry to one Rb(1), one Ba(1), two equivalent Ba(2), and one Ni(1) atom. In the second F site, F(2) is bonded in a 5-coordinate geometry to two equivalent Rb(1), one Ba(1), one Ba(2), and one Ni(2) atom. In the third F site, F(3) is bonded in a distorted linear geometry to one Rb(1), one Ba(2), two equivalent Ba(1), one Ni(1), and one Ni(2) atom.
RbBa2Ni2F9 crystallizes in the trigonal R3m space group. Rb(1) is bonded to three equivalent F(1), three equivalent F(3), and six equivalent F(2) atoms to form distorted RbF12 cuboctahedra that share corners with six equivalent Rb(1)F12 cuboctahedra, corners with three equivalent Ni(1)F6 octahedra, faces with four equivalent Ba(1)F12 cuboctahedra,  a faceface with one Ni(1)F6 octahedra, and faces with three equivalent Ni(2)F6 octahedra. The corner-sharing octahedral tilt angles are 24°. All Rb(1)-F(1) bond lengths are 2.88 Å. All Rb(1)-F(3) bond lengths are 3.12 Å. All Rb(1)-F(2) bond lengths are 2.95 Å. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded to three equivalent F(1), three equivalent F(2), and six equivalent F(3) atoms to form BaF12 cuboctahedra that share corners with six equivalent Ba(1)F12 cuboctahedra, faces with four equivalent Rb(1)F12 cuboctahedra, faces with three equivalent Ni(1)F6 octahedra, and faces with three equivalent Ni(2)F6 octahedra. All Ba(1)-F(1) bond lengths are 2.78 Å. All Ba(1)-F(2) bond lengths are 2.76 Å. All Ba(1)-F(3) bond lengths are 2.94 Å. In the second Ba site, Ba(2) is bonded in a 12-coordinate geometry to three equivalent F(2), three equivalent F(3), and six equivalent F(1) atoms. All Ba(2)-F(2) bond lengths are 2.72 Å. All Ba(2)-F(3) bond lengths are 3.14 Å. All Ba(2)-F(1) bond lengths are 2.98 Å. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to three equivalent F(1) and three equivalent F(3) atoms to form NiF6 octahedra that share corners with three equivalent Rb(1)F12 cuboctahedra, corners with three equivalent Ni(2)F6 octahedra,  a faceface with one Rb(1)F12 cuboctahedra, and faces with three equivalent Ba(1)F12 cuboctahedra. The corner-sharing octahedral tilt angles are 5°. All Ni(1)-F(1) bond lengths are 1.98 Å. All Ni(1)-F(3) bond lengths are 2.09 Å. In the second Ni site, Ni(2) is bonded to three equivalent F(2) and three equivalent F(3) atoms to form NiF6 octahedra that share corners with three equivalent Ni(1)F6 octahedra, faces with three equivalent Rb(1)F12 cuboctahedra, and faces with three equivalent Ba(1)F12 cuboctahedra. The corner-sharing octahedral tilt angles are 5°. All Ni(2)-F(2) bond lengths are 1.98 Å. All Ni(2)-F(3) bond lengths are 2.11 Å. There are three inequivalent F sites. In the first F site, F(1) is bonded in a distorted single-bond geometry to one Rb(1), one Ba(1), two equivalent Ba(2), and one Ni(1) atom. In the second F site, F(2) is bonded in a 5-coordinate geometry to two equivalent Rb(1), one Ba(1), one Ba(2), and one Ni(2) atom. In the third F site, F(3) is bonded in a distorted linear geometry to one Rb(1), one Ba(2), two equivalent Ba(1), one Ni(1), and one Ni(2) atom.