Manganese(VII) oxide (manganese heptoxide) is an inorganic compound with the formula Manganese heptoxide is a volatile liquid with an oily consistency. It is a highly reactive and powerful oxidizer that reacts explosively with nearly any organic compound. It was first described in 1860.[1] It is the acid anhydride of permanganic acid.
The crystalline form of this chemical compound is dark green. The liquid is green by reflected light and red by transmitted light.[2] It is soluble in carbon tetrachloride, and decomposes when in contact with water.
Its solubility properties indicate a nonpolar molecular species, which is confirmed by its structure. The molecules consist of a pair of tetrahedra that share a common vertex. The vertices are occupied by oxygen atoms and at the centers of the tetrahedra are the Mn(VII) centers. The connectivity is indicated by the formula O3Mn−O−MnO3. The terminal Mn−O distances are 1.585 Å and the bridging oxygen is 1.77 Å distant from the two Mn atoms. The Mn−O−Mn angle is 120.7°.[3]
Pyrosulfate, pyrophosphate, and dichromate adopt structures similar to that of . Probably the most similar main group species is . Focusing on comparisons within the transition metal series, and are structurally similar but the Tc−O−Tc angle is 180°. Solid is not molecular but consists of crosslinked Re centers with both tetrahedral and octahedral sites;[4] in the vapour phase it is molecular with a similar structure to Tc2O7.[5]
arises as a dark green oil by the addition of cold concentrated to solid .[2] The reaction initially produces permanganic acid, (structurally,), which is dehydrated by cold sulfuric acid to form its anhydride, :
can react further with sulfuric acid to give the remarkable manganyl(VII) cation, which is isoelectronic with :
decomposes near room temperature, explosively so above 55 °C. The explosion can be initiated by striking the sample or by its exposure to oxidizable organic compounds. The products are and .[6] Ozone is also produced, giving a strong smell to the substance. The ozone can spontaneously ignite a piece of paper impregnated with an alcohol solution.
Manganese heptoxide reacts with hydrogen peroxide in presence of sulfuric acid, liberating oxygen and ozone: