Syntheses, crystal structures and properties of [K(2,2,2-crypt)]3K(HP7)2 · en, [K(18-crown-6)]2HP7 and [K(db18-crown-6)]2HP7 · toluene

The polyphosphide anions in ethylenediamine/2,2,2-crypt, ethylenediamine/18-crown-6 and ethylenediamine/db18-crown-6 solutions are isolated as K[K(2,2,2-crypt)]3(HP7)2 · en (1), [K(18-crown-6)]2HP7 (2) and [K(db18-crown-6)]2HP7 · toluene (3). The mono-protonation of the P7 cluster is observed in all three compounds. The (HP7)2− units are stabilized by naked potassium in 1 and complexing potassium in 2 and 3. The significant C–H⋯P hydrogen bonding interaction is observed in 3, which is responsible for the 3-D supramolecular structure. The 3-D supramolecular structure is also contributed by the η2-interaction between K+ and the phenyl. The 31P and 1H NMR spectra of 1–3 indicate that the polyphosphide anions are very fluxional in solution.

Graphical abstractA series of three new mono-protonated heptaphosphide species, K[K(2,2,2-crypt)]3(HP7)2 · en (1), [K(18-crown-6)]2HP7 (2) and [K(db18-crown-6)]2HP7 · toluene (3) have been synthesized from the ethylenediamine solution of K3P7 in the presence of corresponding sequestering reagents and have been characterized by X-ray crystallography, IR, UV–Vis, 31P and 1H NMR spectra. The unprecedented C–H⋯P hydrogen bonds with the energy of 17–20 kJ/mol have been observed in 3.Figure optionsDownload full-size imageDownload as PowerPoint slide