Theoretical evidence for enhanced NO dimerization in aromatic hosts: implications for the role of the electrophile (NO)(2) in nitric oxide chemistry

Nitric oxide dimerization in gas phase and aromatic hosts (benzene) has been investigated with ab initio quantum mechanics. Using the (RO)MP2-aug-cc-pVDZ method, the computed bond dissociation energy (ON...NO) and geometry of (NO)2 in the gas phase are consistent with the reported spectroscopic data. A relatively strong interaction (-5.4 kcal/mol) between (NO)2 and benzene indicates that aromatic surrounding enhances the NO dimerization. Calculations on reactions of phosphine and methanethiol with NO and (NO)2 show that the dimer is much more reactive. This explains reactions of NO with phosphines and thiols.