Structure and stability of fluoronitrile oxide, FCNO: A quantum-chemical study

The equilibrium geometry, stability, and dimerization of the hitherto unknown fluoronitrile oxide, FCNO, are investigated by various ab initio and density functional methods. The equilibrium geometries are obtained from calculations at the B3LYP, MPn ( n = 2-4), QCISD, QCISD( T), CCSD, and CCSD( T) levels with basis sets ranging from 6-31G* up to cc- pVTZ. Calculations were also performed at selected levels using larger, cc- pVQZ ( B3LYP and MP2) and cc- pV5Z ( B3LYP), basis sets. Potential loss processes for FCNO involving either unimolecular isomerization, or dimerization to a five- membered furoxan ring are investigated at the B3LYP/ 6-311G(2d) level. FCNO is demonstrated to be a feasible synthetic target in the dilute gas phase or matrix.