Phenylchlorocarbene, generated by laser flash photolysis of phenylchlorodiazirine, formed highly stable pi-type complexes with 1,3,5-trimethoxybenzene in pentane. The carbene and carbene complexes were in equilibrium. We measured the equilibrium constant (K = 1264 M-1 at 294 K) and, from its temperature dependence, extracted the associated thermodynamic parameters: Delta H degrees = -7.1 kcal/mol, Delta S degrees = 10.2 eu, and Delta G degrees = 4.1 kcal/mol. The carbene complexes were characterized by UV-vis spectroscopy and computational analysis.