Abstract: A bis[propane 3-bromo-1-(triphenyl phosphonium)] hexamolybdate acetonitrile [PBTPP]2Mo6O19 was prepared and characterized using the following methods: FT-IR, DSC (differential scanning calorimetry), 1H NMR, 13C NMR and single-crystal XRD spectroscopy. The crystal packing of the titled compound as an asymmetrical phosphonium molybdate structure was stabilized by different intermolecular interactions, particularly by the O∙∙∙H-C hydrogen bonds in between [Mo6O19] 2- Lindquist isopolyanion and phosphonium cations. The relative share of different short contacts and 2-Dimension fingerprint maps of the titled compound along with only two symmetric phosphonium-molybdate structures (refcodes: LATGOD and MUPKUG) was taken from CSD (Cambridge Structural Database) were studied by HS analysis. The results showed that in all of these structures, the highest contribution is relevant to the hydrogen bond interactions of oxygen atoms of hexamolybdate anion with the H atom of phenyl moieties of triphenyl phosphonium cation. To evaluate the catalytic efficiency of the above-mentioned compound, aromatic aldehydes (1mmol) were reacted with 2-aminophenol (1mmol) in the presence of the compound [PBTPP]2Mo6O19 (0.125mmol) under solvent-free conditions until 2-substituted benzoxazole derivatives were synthesized with good yields (65%-96%). The compound [PBTPP]2Mo6O19 isolated from the reaction can be reused easily for at least five runs in the synthesis of benzoxazole derivatives, without a significant decrease in its catalytic activity (99%, 95%, 94%, 93%, 90%).This procedure has many preferences, such as simplicity of manipulation, minimization of the catalyst and reaction time, as well as the use of a titled compound as a catalyst with distinguishing features like being green, non-flammable, recyclable and facility to use and store.

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