Synthesis and Structure of a Neutral SiAl14 Cluster

A metastable AlCl solution obtained by co-condensation of the high-temperature molecule AlCl and a mixture of toluene/diethyl ether reacted with SiCp*2 or SiCl4/AlCp*, giving a unique SiAl14 cluster species that bears six Cp* ligands protecting the compound from disproportionation and formation of the bulk material (elemental Al or an Si/Al alloy). The structure of the SiAl14 core represents a section of the body-centered packing where a Si atom resides in the center of an Al cube. Each of the six faces of the cube is capped by an additional Al(η5 Cp*) moiety. This cluster compound was investigated by mass spectrometry, X-ray diffraction, 27Al NMR spectroscopy, and ab initio theory. The solid-state structure contains minor amounts of molecules with additional Cl atoms bonded to the Al atoms at the corners of the cube, and the presence of Cl-containing molecules in the crystal is rationalized on basis of the suggested reaction path.