ELECTRONIC-STRUCTURE OF DIBORANE AND B3H8- - B-H-B BRIDGES AND CLOSED BBB BONDS

Spin-coupled theory is applied to the study of the electronic structure of B2H6 and the B3H8-ion. The resulting wave functions provide a clear picture of the bonding in these systems: In B2H6, highly localized B-H-B bridging bonds appear directly as the result of optimizing the wave function, without the imposition of any preconceptions. Similarly, in B3H8-, a characteristic two-electron three-center BBB bond is seen. A particularly useful feature of this mode of description is its "add-on" nature: The closed three-center two-electron BBB bridging bond found in B3H8- occurs simply in addition to the B-H-B bridging bond, which themselves are very similar to those found in B2H6. The form of these bonds enables us to understand almost all of the unusual features of the nuclear geometry of the B3H8-ion.