An extremely bulky secondary amine, HN(Ar†)(SiPr3i) HL† (Ar† = C6H2{C(H)Ph2}2Pri−2,6,4) has been synthesised and deprotonated with KH in toluene, to afford the potassium amide [KL†(η6-toluene)], which was structurally authenticated. Reaction of this with BBr3 and AlBr3, reproducibly gave the crystallographically characterised amido bromo-borane, [L†B(H)Br], and aluminacycle, [AlBr2{κ2-C,N-N(H)(SiPr3i){C6H2[CPh2][C(H)Ph2]Pri-2,6,4}}], respectively, via ligand C–H activation processes. The known secondary amines, HN(Dip)(Mes) (HLMes) and HN(Dip)(Trip) (HLTrip) (Dip =2,6-diisopropylphenyl, Mes = mesityl, Trip = 2,4,6-triisopropylphenyl), have been structurally characterised, and deprotonated to give the in situ generated lithium amides, [Li(LMes)] and [Li(LTrip)]. Reaction of these with BBr3 and AlBr3 has given the amido group 13 element halide complexes, [LMesBBr2] and [LAlBr2(THF)] (L = LMes or LTrip), the crystal structures of all of which have been determined. Synthetic routes to two new bulky amidine pro-ligands, ArN = C(But)-N(H)Ar, Ar = C6H2{C(H)Ph2}2Me-2,6,4 (Piso*H) or C6H2Pr2i(CPh3)-2,6,4 (Piso″H), have been developed, and the compounds crystallographically characterised. Deprotonation of Piso″H gave the potassium amidinate, [K(Piso″)], which was reacted with BBr3 to give [(Piso″)BBr2]. Reaction of Piso″H with AlMe3 afforded [(Piso″)AlMe2], which, when treated with I2 yielded [(Piso″)AlI2], the crystal structure of which was determined. Reductions of all of the prepared amido and amidinato group 13 element(iii) halide complexes were attempted using a variety of reducing reagents, with a view to prepare boron(i) or aluminium(i) complexes. While these were not successful, this study does offer synthetic inorganic chemists a variety of new very bulky anionic N-donor ligands, and boron/aluminium halide complexes thereof, for use in their own research.
Stereogenic boron in 2-amino-1,1-diphenylethanol-based boronate–imine and amine complexes
