Molecular compounds containing SiAl4, SiAl3, and GeAl4 units: Synthesis and structure of Si(AlCl2 center dot OEt2)(4), Ge(AlCl2 center dot OEt2)(4), and HSi(Cp*AlBr)(3)

In the scope of our investigations of the reactivity and the potential for synthesis of solutions of Al-I halides we performed reactions between these solutions and SiCp2* or GeCp2*, respectively. From these reactions we coul d isolate an unusual cluster with a central Al14Si unit, described elsewher e, and the compounds Si(AlCl2. OEt2)(4), Ge(AlCl2. OEt2)(4), and HSi(Cp*AlB r)(3), which will be presented and discussed here. In these species the Si respectively the Ge atoms are connected to 4 respectively 3 Al atoms. This bonding results in strong negative polarized Si/Ge centres. The change of t he polarization with respect to "normal" Si-R or Ge-R linking leads to a dr astic weakening of the Si-R respectively the Ge-R bonds.