Ininorganic nomenclature, a manganate is any negatively charged molecular entity with manganese as the central atom.[1] However, the name is usually used to refer to the tetraoxidomanganate(2−) anion, MnO2− 4, also known as manganate(VI) because it contains manganese in the +6 oxidation state.[1] Manganates are the only known manganese(VI) compounds.[2]
Other manganates include hypomanganate or manganate(V), MnO3− 4, permanganate or manganate(VII), MnO− 4, and the dimanganate or dimanganate(III) Mn 2O6− 6.
A manganate(IV) anion MnO4− 4 has been prepared by radiolysis of dilute solutions of permanganate.[3][4] It is mononuclear in dilute solution, and shows a strong absorption in the ultraviolet and a weaker absorption at 650 nm.[3]
The manganate(VI) ion is tetrahedral, similar to sulfate or chromate: indeed, manganates are often isostructural with sulfates and chromates, a fact first noted by Eilhard Mitscherlich in 1831.[5] The manganese–oxygen distance is 165.9 pm, about 3 pm longer than in permanganate.[5] As a d1 ion, it is paramagnetic, but any Jahn–Teller distortion is too small to be detected by X-ray crystallography.[5] Manganates are dark green in colour, with a visible absorption maximum of λmax = 606 nm (ε = 1710 dm3 mol−1 cm−1).[6][7] The Raman spectrum has also been reported.[8]
The name "manganite" is used for compounds formerly believed to contain the anion MnO3− 3, with manganese in the +3 oxidation state. However, most of these "manganites" do not contain discrete oxyanions, but are mixed oxides with perovskite (LaMnIIIO3, CaMnIVO3), spinel (LiMnIII,IV 2O4) or sodium chloride (LiMnIIIO2, NaMnIIIO2) structures.
^ abcRush, J. D.; Bielski, B. H. J. (1995), "Studies of Manganate(V), -(VI), and -(VII) Tetraoxyanions by Pulse Radiolysis. Optical Spectra of Protonated Forms", Inorg. Chem., 34 (23): 5832–38, doi:10.1021/ic00127a022
^Lee, Donald G.; Chen, Tao (1989), "Oxidation of hydrocarbons. 18. Mechanism of the reaction between permanganate and carbon-carbon double bonds", J. Am. Chem. Soc., 111 (19): 7534–38, doi:10.1021/ja00201a039.
^ abcPalenik, Gus J. (1967), "Crystal structure of potassium manganate", Inorg. Chem., 6 (3): 507–11, doi:10.1021/ic50049a016.
^ abCarrington, A.; Symons, M. C. R. (1956), "Structure and reactivity of the oxy-anions of transition metals. Part I. The manganese oxy-anions", J. Chem. Soc.: 3373–80, doi:10.1039/JR9560003373
^Lee, Donald G.; Chen, Tao (1993), "Reduction of manganate(VI) by mandelic acid and its significance for development of a general mechanism of dationoxin of organic compounds by high-valent transition metal oxides", J. Am. Chem. Soc., 115 (24): 11231–36, doi:10.1021/ja00077a023.
^Nyholm, R. S.; Woolliams, P. R. (1968), "Manganates(VI)", Inorg. Synth., 11: 56–61
^Sutter, Joan H.; Colquitt, Kevin; Sutter, John R. (1974), "Kinetics of the disproportionation of manganate in acid solution", Inorg. Chem., 13 (6): 1444–46, doi:10.1021/ic50136a037.
^Sekula-Brzezińska, K.; Wrona, P. K.; Galus, Z. (1979), "Rate of the MnO4−/MnO42− and MnO42−/MnO43− electrode reactions in alkaline solutions at solid electrodes", Electrochim. Acta, 24 (5): 555–63, doi:10.1016/0013-4686(79)85032-X.
^Procter, G.; Ley, S. V.; Castle, G. H. (2004), "Barium Manganate", in Paquette, L. (ed.), Encyclopedia of Reagents for Organic Synthesis, New York: Wiley, doi:10.1002/047084289X, hdl:10261/236866, ISBN9780471936237.
^Guziec, Frank S. Jr.; Murphy, Christopher J.; Cullen, Edward R. (1985), "Thermal and photochemical studies of symmetrical and unsymmetrical dihydro-1,3,4-selenadiazoles", J. Chem. Soc., Perkin Trans. 1: 107–13, doi:10.1039/P19850000107
