Pyridinium Pentachloridooxomolybdate(V), (PyH)2[MoOCl5], Revisited: Single-Crystal X-ray Structure Determination

(PyH)2[MoOCl5] was obtained in the form of emerald green crystals unintentionally from (PyH)5[MoOCl4(H2O)]3Cl2 in acetonitrile. (PyH)2[MoOCl5] has been used as a starting material in molybdenum(V) coordination chemistry for decades, yet its true identity has not been known until now. The X-ray structure analysis has undoubtedly confirmed the existence of this compound. The [MoOCl5]2− ion displays the usual structural characteristics of the mononuclear MoO3+-containing compounds.