Pentanitratoaluminate

Pentanitratoaluminate is an anion of aluminium and nitrate groups with formula [Al(NO3)5]2− that can form salts called pentanitratoaluminates.[1] It is unusual being a complex with five nitrate groups, and being a nitrate complex of a light element with nitrate.[1] Such a complex with five nitrate groups is called a pentanitratometallate.[1]

Related complexes

There is a pentanitrato complex with cerium (PPh3Et)2[Ce(NO3)5]. Tetranitratoaluminate and hexanitratoaluminate are related anions with aluminium at their core.

Properties

There are two different arrangements for the coordination of nitrate with aluminium in the complex.[2] One nitrate is bonded with two oxygens to the aluminium (bidentate), and the other five oxygen atoms only link via one oxygen (monodentate). The bidentate nitrate has an O-Al length of 1.98Å. Another two Al-O bonds roughly in the same plane have length of 1.89. The other two Al-O bonds complete a distorted octahedral arrangement and pop out the top and bottom of the aluminium with a length of 1.93Å.[1] The bidentate connected nitrate group is distorted so that the uncoordinated terminal oxygen bond is shorter than the coordinated oxygen-nitrogen distance (1.22 versus 1.31Å). The angles are also warped, with coordinated oxygen angle subtended on the nitrogen of 109°, and angle of these oxygen atoms with the terminal atom of 126°. The whole nitrate is still planar along with the aluminium.[1]

Examples

An example salt is caesium pentanitratoaluminate Cs2[Al(NO3)5].[1] caesium pentanitratoaluminate crystallises in the trigonal form with α=11.16 C=10.02Å formula mass=602.85 with three molecules per unit cell. V=1080Å3, measured density 2.69 g/cm3. The space group is P3121.[1] It is a crystalline substance.

Caesium pentanitratoaluminate has been formed by treating a mixture of caesium chloride and caesium tetracloroaluminate with dinitrogen tetroxide and methyl nitrate, and pumping off the NOCl gas produced.[3] If only caesium tetracloroaluminate is used, omitting the CsCl, then the result contains solid Al(NO3)3.CH3CN as well.[4]

Tetramethylammonium pentanitratoaluminate has been made by recrystalising tetramethyl ammonium tetranitratoaluminate in acetonitrile over several weeks.[5] It forms a waxy substance.

References

  1. 1 2 3 4 5 6 7 D'yachenko, O. A.; L. O. Atovmyan (1975). "The molecular and crystal structure of cesium pentanitratoaluminate". Journal of Structural Chemistry 16 (1): 73–78. doi:10.1007/BF00747552. ISSN 0022-4766.
  2. ↑ Dyachenko, Oleg A.; Lev O. Atovmyan; Galina N. Shirokova; Vadim Ya. Rosolovskii (1973). "X-Ray crystal structure of the pentanitratoaluminate anion". Journal of the Chemical Society, Chemical Communications (16): 595. doi:10.1039/C39730000595. ISSN 0022-4936.
  3. ↑ Jones, CJ Bigler (2007). Transition and Main Group Metals Applied to Oxidative Functionalization of Methane and Use as High Oxygen Carriers for Rocket Propellants. ProQuest. pp. 173–174. ISBN 9780549231066. Retrieved 4 February 2014.
  4. ↑ Jones, CJ Bigler (2007). Transition and Main Group Metals Applied to Oxidative Functionalization of Methane and Use as High Oxygen Carriers for Rocket Propellants. ProQuest. p. 159. ISBN 9780549231066. Retrieved 4 February 2014.
  5. ↑ Jones, CJ Bigler (2007). Transition and Main Group Metals Applied to Oxidative Functionalization of Methane and Use as High Oxygen Carriers for Rocket Propellants. ProQuest. p. 173. ISBN 9780549231066. Retrieved 4 February 2014.
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