ne derivative but an unexpected cyclization product, a stannacyclobutabenzene derivative, in contrast to thereactions of the corresponding dilithiosilane and dilithiogermane, Tbt(Dip)ELi2 (E = Si, Ge), with o-dibromobenzene leading to the formation of the corresponding metallacyclopropabenzenes as stable crystalline compounds. A preliminary result of the synthesis of a tin–tellurium double-bond compound