Extremely Bulky Amido andAmidinato Complexes of Boron and Aluminium Halides: Synthesis and Reduction Studies

An extremely bulky secondary amine, HN(Ary)(SiPr3 i) HLy (AryC6H2{C(H)Ph2}2Pri-2,6,4) has been synthesised and deprotonated with KH in toluene, to afford the potassium amide [KLy(Z6-toluene)], which was structurally authenticated. Reaction of this with BBr3 and AlBr3, reproducibly gave the crystallographically characterised amido bromo-borane, [LyB(H)Br], and aluminacycle, [AlBr2{k 2-C,N-N(H)(SiPr3 i){C6H2[CPh2][C(H)Ph2]Pr i-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, Mesmesityl, Trip 2,4,6-triisopropylphenyl), have been structurally characterised, and depro-tonated 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)] (LLMes or LTrip), the crystal structures of all of which have been determined. Synthetic routes to two new bulky amidine pro-ligands, ArNC(But)-N(H)Ar, ArC6H2{C(H)Ph2}2Me-2,6,4 (Piso*H) or C6H2Pr2i (CPh3)-2,6,4 (Piso00H), have been developed, and the compounds crystallographically characterised. Deprotonation of Piso00H gave the potassium amidinate, [K(Piso00)], which was reacted with BBr3 to give [(Piso 00)BBr2]. Reaction of Piso00H with AlMe3 afforded [(Piso00)AlMe2], which, when treatedwith I2 yielded [(Piso 00)AlI2], the crystal structure ofwhichwas 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