Boraguanidinates: Synthesis, X-ray Structures, and Reactions of {Li2[iPr2NB(NDipp)2]}2 with p-Block and Group 12 Element Halides

Abstract

The new Dipp-substituted boranes (Dipp = 2,6-diisopropylphenyl) (i)Pr2NB(NHDipp)2 (5), BrB(NHDipp)2 (7b), and B(NHDipp)3 (8) have been prepared in high yields and characterized in solution by multinuclear NMR spectroscopy ((1)H, (11)B and (13)C) and in the solid state by X-ray crystallography. Reaction of 5 with 2 equiv of (n)BuLi in n-hexane produces {Li2[(i)Pr2NB(NDipp)2]}2 (6) the first example of a stable dilithiated boraguanidinate. The unsolvated complex 6 has a dimeric structure in the solid state. A survey of the reactions of 6 with p-block and Group 12 element halides revealed various types of reactivity including (a) disproportionation (InCl), (b) reduction to the metal (PbCl2, CdCl2, TeBr4, TeI4, and TlCl), and (c) simple metathesis (GeCl2, MgCl2, and ZnCl2). The metathetical products were characterized by multinuclear NMR spectra but, in contrast to the dilithiated complex 6, they readily decompose in non-coordinating solvents to form the diprotonated compound 5.