MOLECULAR AND ELECTRONIC-STRUCTURES OF (TIXH6)(0 -), X = B, AL, GA, COMPOUNDS/

The molecular and electronic structures of the isomers of both neutral and negative (TiXH6)(0/-), X = B, Al, Ga, systems have been studied. For each of the neutral systems a C-8 isomer of signature (2, 3, 1) (w here (a, b, c) signifies a is the number of terminal Ti-H sends, b, is the number oi. hydrogen bridging bonds, and c is the number of termin al X-H bonds) was characterized as a stable minimum. The X = Al, Ga ne utral systems also had two additional minima of signature (2, 2, 2) (C -2v) and (3, 3, 0) (C-3v) In the anionic cases, each system has a stab le C,structure of signature (3, 2, 1). The X = Al, Ga systems, again s howing more complexity, have minima on their anionic singlet potential energy surfaces of signatures (2, 2, 2), (3, 3, 0), and (3, 0, 3). Th e bonding characteristics of these various minima have been analyzed i n detail through examination of molecular orbitals, natural bond orbit als, and Bader topological analysis. One important structural feature of the stable isomers is that strong hydrogen bridging electron-defici ent bonds are responsible for holding the molecular structure together . For the neutrals, the (2, 3, 1) and (2, 2, 2) isomers have almost th e same energy and the (3, 3, 0) isomer lies more than 30 kcal/mol high er. However, for the anions, the three structures with hydrogen bridgi ng bonds are the most stable and lie very close in energy, within 0.31 kcal/mol for X = Al and within 5.96 kcal/mol for X = Ga. Ionization e nergies and electron affinities have also been calculated and discusse d.