Planar, Twisted, and Trans-Bent:  Conformational Flexibility of Neutral Diborenes

Abstract

The potassium graphite reduction of R‘BBr 3 (R‘ =:C{N(2,4,6-Me 3 C 6 H 2 )CH} 2 ) in Et 2 O led to the isolation of 3 (R‘(H)B B(H)R‘) and 4 (R‘(H) 2 B−B(H) 2 R‘), with B B double and B−B single bonds, respectively. These compounds were characterized by single-crystal X-ray diffraction, 1 H and 11 B NMR, and elemental analyses. Neutral diborene 3 exhibits polymorphic planar ( 3a ), twisted ( 3b ), and trans-bent ( 3c ) geometries in the solid state.