Search

The synthesis and isolation of the first stable C-B-N-substituted borinium [MesBNiPr2][B(C6F5)4] (2) is described. Compound 2 was shown to react with isothiocyanate and carbodiimides, effecting B-C insertion to afford nitrilium (4) and borenium amidinate salts, respectively. The borinium cation [MesBNiPr2]+ (2+) was also generated from reactions of MesB(Cl)NiPr2 (1) and GaCl3, and used to prepare stable borenium amidinate salts (5-6), while the triflate borane MesB(OTf)NiPr2 (7) reacts with carbodiimide to give the bis(amidinate) boronium salt [MesC(NiPr)2B((NiPr)2C)NiPr2][OTf] (8).

The mechanochemical synthesis of tertiary and secondary alanes AlR3 (R = Np 1 or Mes 2; HAlR2 R = Np 3 or Mes 4) is described. These species are reacted with several α-diimines to give a series of aluminium-derived radicals of the form [(diimine)AlR2]˙ (6–11). EPR and several crystallographic studies are reported. These species are thought to form via hydro- or carboalumination and subsequent elimination reactions. This view is supported by the structural data for minor products C12H7(NHDipp)(NDipp)AliBu25 and C13H8(C(iBu)N(m-Xy)(NH(m-Xy)))AliBu212. In addition, the characterization of (C6F5)2B(OC(C6F5)OC12H8) indicates that such a carboboration pathway also provides access to related boron-derived radicals.

Redox active, or non-innocent, ligands containing O or N heteroatoms are frequently used in transition metal complexes, imparting unique catalytic properties, but have seen comparatively limited use in the chemistry of group 13 elements. In this article we report the frustrated Lewis pair (FLP) hydrogenation and hydroboration of an N-aryl-phenanthrene-o-iminoquinone and two N,N′-diaryl-phenanthrene α-diimines. These reactions exploit B(C6F5)3/H2, HB(C6F5)2 and H2BC6F5·SMe2 to give a series of derivatives including 1,3,2-oxaza- and diazaboroles and borocyclic radicals. The reaction pathways leading to these products are outlined and supported by DFT-calculations and experimental insight. The modular and unusual synthetic strategies described herein give access to new boroles as well as air-stable boron-containing radicals, thus extending the chemistry of redox active ligands in main group systems.