Synthesis and Structure of an <i>o</i>‐Carboranyl‐Substituted Three‐Coordinate Borane Radical Anion
Johannes Krebs, Martin Haehnel, Ivo Krummenacher, Alexandra Friedrich, Holger Braunschweig, Maik Finze, Lei Ji, Todd B. Marder
Abstract
Abstract Bis(1‐(4‐tolyl)‐carboran‐2‐yl)‐(4‐tolyl)‐borane [(1‐(4‐MeC 6 H 4 )‐ closo ‐1,2‐C 2 B 10 H 10 ‐2‐) 2 (4‐MeC 6 H 4 )B] ( 1 ), a new bis( o ‐carboranyl)‐(R)‐borane was synthesised by lithiation of the o ‐carboranyl precursor and subsequent salt metathesis reaction with (4‐tolyl)BBr 2 . Cyclic voltammetry experiments on 1 show multiple distinct reduction events with a one‐electron first reduction. In a selective reduction experiment the corresponding paramagnetic radical anion 1 .− was isolated and characterized. Single‐crystal structure analyses allow an in‐depth comparison of 1 , 1 .− , their calculated geometries, and the S 1 excited state of 1 . Photophysical studies of 1 show a charge transfer (CT) emission with low quantum yield in solution but a strong increase in the solid state. TD‐DFT calculations were used to identify transition‐relevant orbitals.