CYCLOPENTADIENYLIDENECARBENE - A STABLE ISOMER OF ORTHO-BENZYNE

High-level ab initio quantum-mechanical studies have been performed on cyclopentadienylidenecarbene, an experimentally unknown species thought to be an important isomerization product omicron-benzyne. Results suggest that cyclopentadienylidenecarbene is a shallow minimum on the PE surface, being bound by less than 5 kcal mol-1. Harmonic vibrational frequencies have been evaluated at the self-consistent (SCF) level, together with the singlet-triplet energy difference, electron affinity, and lowest ionization energy at the configuration interaction (CI) level. The study provides the valuable detail and insight into cyclopentadienylidenecarbene necessary for its experimental detection and characterization.