Diboryldiborenes: π‐Conjugated B4 Chains Isoelectronic to the Butadiene Dication.

Abstract: B(sp2)–B(sp3) diborane species based on bis(catecholato)diboron and N‐heterocyclic carbenes (NHCs) underwent catechol/bromide exchange selectively at the sp3‐hybridized boron atom. The reduction of the resulting 1,1‐dibromodiborane adducts led to reductive coupling and isolation of doubly NHC‐stabilized 1,2‐diboryldiborenes. These compounds are the first examples of molecules exhibiting π‐electron delocalization over an all‐boron chain. [ABSTRACT FROM AUTHOR]