New Volatile Nitronium Nitratometalates: NO2[Fe(NO3)4] and NO2[Zr(NO3)5] — Synthesis and Crystal Structure

Crystalline NO₂Fe(NO₃)₄] was obtained by dehydration of a solution of Fe(NO₃)₃ in 100 % HNO₃ and subsequent sublimation. NO₂Zr(NO₃)₅] was synthesized by reaction of ZrCl₄ with N₂O₅ followed by sublimation in vacuum. X‐ray single crystal structure determination showed both compounds to consist of nitronium cations, NO₂⁺, and nitratometalate anions. N‐O distances in the linear NO₂⁺ cations are in the range of 1.08—1.13Å. In both Fe(NO₃)₄]^? and Zr(NO₃)₅]^? anions, all nitrate groups are coordinated bidentately with average M‐O distances 2.134 and 2.293Å, respectively. Taking into account the position of N atoms around the M atoms, the arrangement of nitrate groups can be described as tetrahedral for the Fe complex and trigonal‐bipyramidal for the Zr complex. There are four shortest N(nitronium)····O(nitrate group) contacts with average distances of 2.705 and 2.726Å in NO₂Fe(NO₃)₄] and 2.749Å in NO₂Zr(NO₃)₅]. Nitronium pentanitratohafnate is isotypic to the zirconium complex.