Gallium derivatives of tetraborane(10): can bis(digallanyl) isomers exist?

All derivatives of tetraborane(10) with one or more boron atoms replaced by gallium have been investigated using quantum chemical methods. Particular attention is given to the relative stability of the 'butterfly' arachno- st ructures and the bis(diboranyl) structures. It is concluded that these two structures have very close energies if the bis(diboranyl) structures contai n a central gallium-gallium bond. These gallium substituted bis(diboranyl) structures are thus a fascinating synthetic target.