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O- and/or H-bridged aluminum centersare found in the multinuclear alanes presented here. A peculiarity is the cage compound 1(crystal structure shown on the right), in which allAl atoms are pentacoordinated. This is the first molecular compound with a tetracoordinated hydride ion.

Blue-black trisupersilyldigallanyl, a new metastable inorganic radical, forms in the reaction of GaCl3with tBu3SiNa in pentane at room temperature according to Equation (a). The X-ray structure analysis reveals that it contains a planar Si2GaIIGaIand a nearly linear GaIIGaISi framework; according to the ESR spectrum the unpaired electron resides in both Ga atoms. Surprisingly, the analogous reaction of AlCl3and tBu3SiNa (Al instead of Ga in Equation (a)) does not lead to trisupersilyldialanyl, but to red tetrasupersilyldialane (tBu3Si)2Al–Al(SitBu3)2.

What looks like a scoop wheelon the right are seven ferrocene units, which are linked by four Me2Si groups to the two nearest neighbors. The cycle, which is formed in a polygemination reaction (that is, the reaction of a transition metal halide with a biscyclopentadienyl dianion to give a polymer), has the rare C7hsymmetry (idealized). The compound is stable up to 360°C and can be oxidized in three steps up to a heptacation.