Inorganic Chemistry

The structure of a pentachromium(II) extended metal atom chain at 3 K: Cotton’s conjecture proven



We provide definitive experimental proof that prototypical string-like compound [Cr5(tpda)4(NCS)2] has alternating long and short Cr-Cr separations in the solid state, as conjectured by F. A. Cotton, rather than essentially equally spaced Cr atoms, as initially claimed (H2tpda = N2,N6-di(pyridin-2-yl)pyridine-2,6-diamine). Single-crystal X-ray data collected from 292 to 3 K revealed that the misinterpretation is caused by pseudo-merohedral twinning and that bond length alternation is enhanced at low temperature.


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Supplementary material

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Electronic Supplementary Information
Synthetic and crystallographic details, additional plots of temperature-dependent structural parameters.