The CO2-N2 Dimer etc., Stability

B3LYP/6-31G andMP2/6-31G optimization/frequency calculations agree that  

The cyclic CO2 dimer is expected to require veiy low, possibly matrix isolation, temperatures for its observation, and a low-temperature photochemical synthesis by extmsion of CO2 from the cyclic trimer was suggested. The trimer and the acyclic species may be isolable at somewhat higher temperatures, and may be pteparable by dehydration of carbonic acid. 

The synthesis of the CO2-N2 compounds is a formidable challenge, largely because of the synthetic difficulties associated with N-O bonds. Nevertheless, syntheses of the monocyclic (C02)2N2 were suggested. 

Practical Strategies for Electronic Structure Calculations , Wavefunction, Inc., Irvine, CA, 1995 chapter 4. 

Pyykko, Chem. Commun., J. Chem. Soc., Chem. Commun., 1999, 6, 495. 

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