Syntheses and structures of piperazin-1-ium ABr₂ (A = Cs or Rb): hybrid solids containing `curtain wall' layers of face- and edge-sharing ABr₆ trigonal prisms

Abstract

The isostructural title compounds, poly[piperazin-1-ium [di-μ-bromido-caesium]], {(C4H11N2)[CsBr2]} n , and poly[piperazin-1-ium [di-μ-bromido-rubidium]], {(C4H11N2)[RbBr2]} n , contain singly-protonated piperazin-1-ium cations and unusual ABr6 (A = Cs or Rb) trigonal prisms. The prisms are linked into a distinctive `curtain wall' arrangement propagating in the (010) plane by face and edge sharing. In each case, a network of N—H...N, N—H...Br and N—H...(Br,Br) hydrogen bonds consolidates the structure.

Ino-Chloridolithates from Ionothermal Synthesis

“…Due to the high differences in electronegativities, the high lattice energies of (pseudo)­binary salts, as well as the energetic unavailability of d -orbitals, alkali metal ions are underrepresented in coordination chemistry and are rarely known to form anionic metalates. Only a few rather counterintuitive examples were reported for the heavier elements K, Rb, and Cs: [U 2 (CN) 3 (NH 3 ) 14 ]­[KBr 6 ], (H 2 dabco )­[KCl 3 ] (dabco = 1,4-diazabicyclo[2.2.2]­octane), ( HPP )­[MBr 2 ] (HPP = piperazin-1-ium, M = Rb, Cs), and the perovskitic compounds ( Cat )­[MX 3 ] (Cat = 1-methylpiperizine-1,4-diium, 3-ammoniopyrrolidinium, dabco derivatives; M = K, Rb, Cs; X = Cl, Br, I). − The only lithium-containing compounds in this regard were obtained from molten salt syntheses in the presence of larger metal cations: M­[LiX 2 ] (M = Rb, Cs; X = F, Cl, Br), − Cs 2 [Li 2 Cl 3 ], Cs 3 [Li 2 Cl 5 ], Cs 2 [Li 3 I 5 ], Gd­[LiCl 4 ], and M­[LiF 4 ] (M = Y, Bi, Eu–Lu). − Additionally, a variety of organometallic lithate salts, such as [Li­(C­(SiMe 3 ) 3 ) 2 ] − , [Li­(N­(SiMe 3 )) 2 (SPh) 2 ] − , and [Li 2 ( diglyme )­(C 4 H 3 S) 3 ] − , are known.…”