Nitrogen Dioxide NO2 Dinitrogen Tetroxide N2O4

 Synthesis
 
 Pb(NO3)2  PbO + 2NO2 + 1/2O2
 
 
Structure
 
 
 
Liq NO2, can get anhydrous nitrates
 
Cu + 3N2O4  Cu(NO3)2.(N2O4) + 2NO