Ab initio electronic structure calculations on chlorocarbene-ethylene and chlorocarbene-benzene complexes

Interaction energies for carbene-solvent complex formation have been comput ed at the MP2/6-311+G**//MP2/6-31G* level, including full counterpoise corr ections. Our results indicate that chlorocarbenes do not form stable comple xes with ethylene at ambient temperatures and react with tetramethylethylen e to form cyclopropanes without an activation energy barrier. Chlorocarbene s and benzene form weakly interacting but thermally stable 1:1 and 1:2 pi-t ype complexes. Two pi-type complexes and a hydrogen-bonded ylidic structure were obtained for the 1:1 methylchlorocarbene-anisole system. The formatio n of carbene-solvent complexes might modulate carbenic reactivity in aromat ic solvents.