Generation and Reactions of Overcrowded Diaryldilithiostannane and Diaryldipotassiostannane

Exhaustive reduction of an overcrowded dibromostannane bearing two bulky aromatic substituents, Tbt(Dip)SnBr 2 {Tbt = 2,4,6‐tris[bis(trimethylsilyl)methyl]phenyl; Dip = 2,6‐diisopropylphenyl}, with an excess amount of lithium naphthalenide in THF at –78 °C gave the corresponding dilithiostannane, Tbt(Dip)SnLi 2 , the generation of which was confirmed by trapping experiments with some electrophiles together with 119 Sn and 7 Li NMR spectroscopy. The diaryldilithiostannane was found to be stable in solution under an inert gas below –25 °C. The potassium analogue, Tbt(Dip)SnK 2 , was also generated by the reduction of the dibromostannane in THF at –78 °C by the use of KC 8 as a reductant. The reactions of dilithiostannane and dipotassiostannane obtained with o ‐dibromobenzene did not give a stannacyclopropabenzene derivative but an unexpected cyclization product, a stannacyclobutabenzene derivative, in contrast to thereactions of the corresponding dilithiosilane and dilithiogermane, Tbt(Dip)ELi 2 (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 from the dilithiostannane is also presented. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)