Reduction of Phenyl Silyl Acetylenes with Lithium: Unexpected Formation of a Dilithium Dibenzopentalenide

摘要

The 1,4-dilithio-1,3-butadiene that is obtained from phenylacetylene with lithium[1] is often employed as the starting compound for the synthesis of metal-containing carbocyclic π systems, for example, Group 14 metalloles.[2] X-ray crystal structure analyses of 1,4-dithio-1,3-butadienes have shown that these compounds are monomeric with two bridging lithium ions.[3] The pentalene dianion, on the other hand, has received considerable attention as a ligand of sandwich-type transition-metal complexes.[4], [5] However, the dibenzopentalene dianion, which is π extended to a greater degree than the pentalene dianion, has received less attention in spite of its potential usefulness as a building block for ladder-type π-conjugated molecules of growing interest.