New structures of low valent Al hypersilanides: A negatively charged isomer with a closo-Al4Si-structure potentially indicates a new entry in polyhedral AlmSin-frameworks

The reaction of lithium tris(trimethylsilyl)silanide with donor stabilized monovalent aluminium bromide leads to two isomeric closed polyhedral aluminium anions as reduction products (1a and 1b) and two new fourth-coordinate anionic aluminium(III) oxidation products (3 and 4). Evidence for a rearrangement reaction between the anionic polyhedral aluminium isomers is given. All of the structurally characterized compounds contain [Li(thf)4]+ as counter cations in their neutral crystal lattices.

The trigonal bipyramidal Al3[Si(SiMe3)3]3AlSi(SiMe3)Si(SiMe3) monoanion 1a is the first example for a closo polyhedron, which contains exclusively atoms from the neighbouring elements aluminium and silicon. The synthesis and structural characterization of 1a and of a further structural isomer of this Al4Si-cluster compound (1b) will be described in the paper.Figure optionsDownload as PowerPoint slide