Electron capture of tetracyanoethylene oxide in the gas phase. Rearrangement of the parent radical anion to form [(NC)(3)C](-). A joint experimental and ab initio study

Capture of an electron by tetracyanoethylene oxide can initiate a number of decomposition pathways. One of these decompositions yields [(NC)(3)C](-) a s the ionic product. Ab initio calculations (at the B3LYP/6-31 + G* level o f theory) indicate that the formation of [(NC)(3)C](-) is initiated by capt ure of an electron into the LUMO of tetracyanoethylene oxide to yield the a nion radical [(NC)(2)C-O-C(CN)(2)](-.) that undergoes internal nucleophilic substitution to form intermediate [(NC)(3)C-OCCN](-.). This intermediate d issociates to form [(NC)(3)C](-) (m/z 90) as the ionic product. The radical (NC)(3)C-. has an electron affinity of 4.0 eV (385 kJ mol(-1)). Ab initio calculations show that [(NC)(3)C](-) is trigonal planar with the negative c harge mainly on the nitrogens. A pictorial representation of this structure is the resonance structure formed from three degenerate contributing struc tures (NC)(2)-C=C=N-. The other product of the reaction is nominally (NCCO) (.), but there is no definitive experimental evidence to indicate whether t his radical survives intact, dr decomposes to NC. and CO. The overall proce ss [(NC)(2)C-O-C(CN)(2)](-.) --> [(NC)(3)C](-) + (NCCO)(.) is calculated to be endothermic by 21 kJ mol(-1) with an overall barrier of 268 kJ mol(-1). (Int J Mass Spectrom 194 (2000) 165-170) (C) 2000 Elsevier Science B.V.