Alkylindium subhalides derived from the tetrahedral indium(I) cluster compound [In4[C(SiMe3)3]4]

Partial oxidation of the tetraalkyltetraindium(I) compound In4[C(SiMe3)3]4] 1 with halogen donors such as 1,2-dibromoethane and hexachloroethane or with mixtures of bromine and aluminum tribromide afforded novel alkylindium halides in which the indium atoms still possess unusually low oxidation states. Indium-indium single bonds between bivalent indium atoms were found in the compounds In2X2R2 (R = C(SiMe3)3, X = Cl (2) or Br (4)), which gave dimers in the solid state with all four halogen atoms in a bridging position. The tetrahedral arrangement of four indium atoms in a cluster was retained in the compound In4Br2R4 (3), in which one bromine atom occupied a mu3-bridging position above one triangular face of the In4 tetrahedron. One edge of that triangle was bridged by the second bromine atom. Mixed-valent indium atoms resulted with an average oxidation state of + 1.5.