Tetrasilyl-substituted cyclobutadiene dianion dilithium salt:synthesis and structure

摘要

The reaction of tetrakis(trimethylsilyl)cyclobutadienylcyclopentadienyl cobalt complex (Me_3Si)_4C_4CoCp with lithium metal in THF yielded the dilithium salt of cyclobutadiene dianion CBD~(2-) stabilized by four trimethylsilyl groups,Li~+_2[(Me_3Si)_4C_4]~(2-).The bridged CBD~(2-) dianion was also synthesized by a similar procedure starting from the bridged cobalt complex,which was prepared from the reaction of 2,2,5,5,8,8,ll,ll-octamethyl-2,5,8,ll-tetrasilacyclododeca-1,6-diyne with CpCo(CO)_2 in refluxing octane.The aromaticity of the CBD~(2-) is discussed on the basis of the structural characteristics and magnetic properties.