[Rutherford]

For the reaction 2Cl₂O+2N₂O₅ 2NO₃Cl+2NO₂Cl+O₂ experimental data has given the following rate law: r=k[N₂O₅]. Devise a mechanism for this reaction.

The first step should be:
N₂O₅ ... (slow)
As in the reaction 2 equivalents of N₂O₅ appear, N₂O₅ should react with one product of the first step. Here I am stuck. I tried with N₂O₃ & O₂, NO₃ & NO₂, N₂O₄ & 1/2O₂. Only N₂O₃ could react with N₂O₅ to form maybe 2N₂O₄, but what then (I can't avoid a at least three-molecular reaction)? Any ideas? Or the products were some other species?