Abstract
A new alumaborane compound containing a {AlH-BH} functional group has been prepared by reaction of the aluminium(I) complex [{(ArCMeN)(2)CH}Al] (Ar = 2,6-i-Pr(2)C(6)H(3)) with a boron dihydride species supported by an anionic chelating κ(2)-N,N ligand. Spectroscopic analysis of the product suggests that it exists as a mixture of isomers in solution with the ligand on boron coordinating in both a κ(1) and κ (2) fashion. The dialumane analogue, containing a {AlH-AlH} functional group, was also prepared. Comparison of the structure and bonding of these species by DFT calculations suggests that reactivity of the AlH-BH moiety should be governed by the nucleophilicity of the Al-H and Al-B bonds along with the Lewis acidity imparted by the partially available 2p of boron. Chemoselective reactions are observed with CO(2), CNXyl (Xyl = 2,6-Me(2)C(6)H(3)), and PhCN. While CO(2) inserts selectively into the Al-H bond to generate a formate, the more Lewis basic substrates CNXyl and PhCN react through initial coordination at boron and insertion into the Al-B bond. In the case of PhCN, an unusual pathway to generate 1,3,2-diazaborole compound is reported. Our work delivers the first insight into the reactivity of the {AlH-BH} functional group and provides a rational framework for further developments.