Tetracarba-nido-hexaborane

Tetraalkyl-l,6-dihalogeno-2,3,4,5-tetracarba-nido-hexaboranes(6) 56d were obtained in high yield by another route (Scheme 3.2-30), taking advantage of the exchange reactions of the spirotin compounds 57 with boron halides. 

Reductive opening of a tetracarba-nido-hexaborane cluster to an arachno-dianion was described for 56g, which is accessible by thermal elimination of bis(trime-thylsilyl)ethyne from the bridged bishomoborirene 61 [82], Reaction of 56g with elemental lithium in THF gives [(Li thf)2]l,3-diboratabenzene 62, its reoxidation to 56g requires boiling 1,2-dibromoethane (Scheme 3.2-33). 

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