Bis(1,2,3-trimethylpyridinium) Octa(μ2-bromido)Tetrabromidopentacuprate(II): Linear, Quasi-Planar Pentacopper(II) Oligomers Stacked to Form Egg-Tray Layers

Abstract

The crystal structure of (1,2,3-trimethylpyridnium)2Cu5Br12 provides the second reported example of a fully halogenated, linear, quasi-planar, bibridged pentacopper(II) oligomer. The oligomers are aggregated into crosshatched layers that defy traditional notions and notations for quasi-planar oligomer stacking. The regularly arranged voids in the layers are occupied by inversion-related organic cation pairs similar to eggs in an egg-tray. The cross-hatched layer structure arises from a particular stacking of mixed organic cation/pentacopper oligomer sheets. The sheets consist of oligomers placed in a herringbone arrangement separated by zipper-like ribbons of organic cations in a structural motif similar to that found in other 1,2,3- or 1,2,6-trimethylpyridinium halidocuprate(II) structures. Alternative stacking of the sheets leads, on the other hand, to a conventional stacking pattern that conforms to traditional stacking descriptions. Interpretation of these structures in terms of the stacking of mixed cation/anion sheets, as is often performed for ABX3 systems, provides a complementary method for understanding these structures as well as providing a means to describe systems that are not easily described by traditional stacking notation.