A neutral stannaaromatic compound, 9-stannaphenanthrene la bearing an efficient steric protection group, 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl (Tbt), was successfully generated by the reaction of the corresponding chlorostannane 2 with lithium 2,2,6,6-tetramethylpiperidide in THF at -78 degrees C. The generaion of la was indicated by the trapping experiments using MeOD, Mes*CNO, and 2,3-dimethyl-1,3-butadiene at the same temperature. However, la was found to undergo ready dimerization at room temperature to give the cis-[2 + 2] dimer 3 stereoselectively.