Ammonium perrhenate

Structure

The crystal structure of APR resembles that of scheelite, with atomic cation is replaced by ammonium. The pertechnetate (NH4TcO4), periodate (NH4IO4), tetrachlorothallate (NH4TlCl4), and tetrachloroindate (NH4InCl4) follow this motif. It undergoes a molecular orientational ordering transition on cooling without change of space group, but with a highly anisotropic change in the shape of the unit cell, resulting in the unusual property of having a positive temperature and pressure Re NQR coefficient. APR does not give hydrates.

Preparation

Ammonium perrhenate may be prepared from virtually all common sources of rhenium. The metal, oxides, and sulfides can be oxidized with nitric acid and the resulting solution treated with aqueous ammonia. Alternatively an aqueous solution of Re2O7 can be treated with ammonia followed by crystallisation.

Reactions

Ammonium perrhenate is weak oxidizer. It slowly reacts with hydrochloric acid: :NH4ReO4 + 6 HCl → NH4[ReCl4O] + Cl2 ↑ + 3H2O. It is reduced to metallic Re upon heating under hydrogen: :2 NH4ReO4 + 7 H2 → 2 Re + 8 H2O + 2 NH3 Ammonium perrhenate decomposes to volatile Re2O7 starting at 250 °C. When heated in a sealed tube at 500 °C, It decomposes to rhenium dioxide: :2NH4ReO4 → 2ReO2 + N2 + 4 H2O The ammonium ion can be displaced with some concentrated nitrates e.g. potassium nitrate,, silver nitrate, etc.: :NH4ReO4 + KNO3 → KReO4 ↓ + NH4NO3 It can be reduced to nonahydridorhenate with sodium in ethanol: :NH4ReO4 + 18Na + 13C2H5OH → Na2[ReH9] + 13NaC2H5O + 3NaOH + NH3•H2O.

References

References

1. Georg Brauer. (1954). "Ammoniumperrhenat". Ferdinand Enke Verlag.
2. Lidin, R.. (2007). "Неорганическая химия в реакциях". Drofa.
3. Noddack, J.. (1929). "Die Sauerstoffverbindungen des Rheniums". Zeitschrift für anorganische und allgemeine Chemie.
4. I. P. Swainson and R. J. C. Brown. (1997). "Refinement of ammonium perrhenate structure using a pseudo-spin model for the ammonium ion orientation". [[Acta Crystallographica]].
5. R. J. C. Brown and S. L. Segel. (1977). "¹⁸⁷Re, ¹⁴N, and ²H nuclear quadrupole couplings in NH₄ReO₄: Evidence for a possible phase transition". [[Journal of Chemical Physics]].
6. O. Glemser "Ammonium Perrhenate" in ''[https://archive.org/details/Handbook_of_Preparative_Inorganic_Chemistry_1_2_Brauer Handbook of Preparative Inorganic Chemistry]'', 2nd Ed. Edited by G. Brauer, Academic Press, 1963, New York. vol. 1. p. [https://archive.org/details/Handbook_of_Preparative_Inorganic_Chemistry_1_2_Brauer/page/n1522 1476]–85.
7. Richard J. Thompson. (1966). "Inorganic Syntheses".