Redox-Controlled Reactivity at Boron: Parallels to Frustrated Lewis/Radical Pair Chemistry.

We report the synthesis of new Lewis-acidic boranes tethered to redox-active vanadium centers, (PhN)V(μ-N)B(CF) () and (N(CHCHN(CF)))V(μ-N)B(CF) (). Redox control of the V couple resulted in switchable borane versus "hidden" boron radical reactivity, mimicking frustrated Lewis versus frustrated radical pair (FLP/FRP) chemistry, respectively. Whereas heterolytic FLP-type addition reactions were observed with the V complex () in the presence of a bulky phosphine, homolytic peroxide, or Sn-hydride bond cleavage reactions were observed with the V complex, [CoCp][(N(CHCHN(CF)))V(μ-N)B(CF)] (), indicative of boron radical anion character. The extent of radical character was probed by spectroscopic and computational means. Together, these results demonstrate that control of the V oxidation states allows these compounds to access reactivity observed in both FLP and FRP chemistry.