Anion stabilised hypercloso-hexaalane Al6H6

Abstract

Boron hydride clusters are an extremely diverse compound class, which are of enormous importance to many areas of chemistry. Despite this, stable aluminum hydride analogues of these species have remained staunchly elusive to synthetic chemists. Here we report that reductions of an amidinato-aluminum(III) hydride complex with magnesium(I) dimers lead to unprecedented examples of stable aluminum(I) hydride complexes, [(ArNacnac)Mg]2[Al6H6(Fiso)2] (ArNacnac = [HC(MeCNAr)2]-, Ar = C6H2Me3-2,4,6 Mes; C6H3Et2-2,6 Dep or C6H3Me2-2,6 Xyl; Fiso = [HC(NDip)2]-, Dip = C6H3Pri2-2,6), which crystallographic and computational studies show to possess near neutral, octahedral hypercloso-hexaalane, Al6H6, cluster cores. The electronically delocalized skeletal bonding in these species is compared to that in the classical borane, [B6H6]2-. Thus, the chemistry of classical polyhedral boranes is extended to stable aluminium hydride clusters for the first time.