Pentafluorophenylchlorocarbene, generated by laser flash photolysis (LFP) of pentafluorophenylchlorodiazirine, formed pi-type complexes with 1,3,5-trimethoxybenzene in pentane. The carbene and carbene complexes were in equilibrium with K = 3.21 x 10(5) M(-1) at 294 K From the temperature dependence of K, Delta H degrees = -10.2 kcal/mol, Delta S degrees = 9.5 eu, and Delta G degrees = -7.4 kcal/mol at 298 K The carbene complexes were characterized by UV-vis spectroscopy and computational analysis.