Beschreibung:
<jats:p>Three nine-bond arrangements which are not forbidden in spd hybridization are described. Of these, the tripyramidal arrangement is discussed in detail since it seems most favorable stericly. In this arrangement there are two types of orbitals, six trigonal prism orbitals and three equatorial orbitals. When the average orbital strength is greatest, it equals 2.983. Some light is thrown on the following structures: TaF7−2, OsF8, and conjectural OsF9−.</jats:p>