RbHf2Br9 crystallizes in the monoclinic P2/c space group. Rb(1) is bonded to two equivalent Br(1), two equivalent Br(4), four equivalent Br(2), and four equivalent Br(5) atoms to form distorted RbBr12 cuboctahedra that share corners with four equivalent Hf(1)Br6 octahedra, edges with four equivalent Rb(1)Br12 cuboctahedra, edges with two equivalent Hf(1)Br6 octahedra, and faces with two equivalent Hf(1)Br6 octahedra. The corner-sharing octahedral tilt angles range from 12-42°. Hf(1) is bonded to one Br(1), one Br(2), one Br(3), one Br(5), and two equivalent Br(4) atoms to form HfBr6 octahedra that share corners with two equivalent Rb(1)Br12 cuboctahedra,  an edgeedge with one Rb(1)Br12 cuboctahedra,  a faceface with one Rb(1)Br12 cuboctahedra, and  a faceface with one Hf(1)Br6 octahedra. There are five inequivalent Br sites. In the first Br site, Br(1) is bonded in a distorted water-like geometry to one Rb(1) and one Hf(1) atom. In the second Br site, Br(2) is bonded in a distorted single-bond geometry to two equivalent Rb(1) and one Hf(1) atom. In the third Br site, Br(3) is bonded in an L-shaped geometry to two equivalent Hf(1) atoms. In the fourth Br site, Br(4) is bonded in an L-shaped geometry to one Rb(1) and two equivalent Hf(1) atoms. In the fifth Br site, Br(5) is bonded in a distorted single-bond geometry to two equivalent Rb(1) and one Hf(1) atom.
RbHf2Br9 crystallizes in the monoclinic P2/c space group. Rb(1) is bonded to two equivalent Br(1), two equivalent Br(4), four equivalent Br(2), and four equivalent Br(5) atoms to form distorted RbBr12 cuboctahedra that share corners with four equivalent Hf(1)Br6 octahedra, edges with four equivalent Rb(1)Br12 cuboctahedra, edges with two equivalent Hf(1)Br6 octahedra, and faces with two equivalent Hf(1)Br6 octahedra. The corner-sharing octahedral tilt angles range from 12-42°. Both Rb(1)-Br(1) bond lengths are 3.68 Å. Both Rb(1)-Br(4) bond lengths are 4.09 Å. There are two shorter (3.79 Å) and two longer (4.10 Å) Rb(1)-Br(2) bond lengths. There are two shorter (3.81 Å) and two longer (3.88 Å) Rb(1)-Br(5) bond lengths. Hf(1) is bonded to one Br(1), one Br(2), one Br(3), one Br(5), and two equivalent Br(4) atoms to form HfBr6 octahedra that share corners with two equivalent Rb(1)Br12 cuboctahedra,  an edgeedge with one Rb(1)Br12 cuboctahedra,  a faceface with one Rb(1)Br12 cuboctahedra, and  a faceface with one Hf(1)Br6 octahedra. The Hf(1)-Br(1) bond length is 2.49 Å. The Hf(1)-Br(2) bond length is 2.51 Å. The Hf(1)-Br(3) bond length is 2.72 Å. The Hf(1)-Br(5) bond length is 2.52 Å. There is one shorter (2.73 Å) and one longer (2.75 Å) Hf(1)-Br(4) bond length. There are five inequivalent Br sites. In the first Br site, Br(1) is bonded in a distorted water-like geometry to one Rb(1) and one Hf(1) atom. In the second Br site, Br(2) is bonded in a distorted single-bond geometry to two equivalent Rb(1) and one Hf(1) atom. In the third Br site, Br(3) is bonded in an L-shaped geometry to two equivalent Hf(1) atoms. In the fourth Br site, Br(4) is bonded in an L-shaped geometry to one Rb(1) and two equivalent Hf(1) atoms. In the fifth Br site, Br(5) is bonded in a distorted single-bond geometry to two equivalent Rb(1) and one Hf(1) atom.