Molecular Orbitals in Some Boron Compounds

An LCAO treatment of boron framework orbitals in B10H14 yields a charge distribution of +0.05e on atoms 1 and 3, of —0.25e on atoms 2 and 4, of —0.03e on atoms 5, 7, 8, and 10, and of +0.27e on atoms 6 and 9. When a charge of about —0.2e is assigned to each bridge H atom, the order of reactivity agrees with that expected from the chemical behavior (neg 2,4<1,3<5,7,8,10<6,9 pos). An LCAO investigation of boron orbitals in the B5H5 molecule of D3h symmetry and with nine equal B–B distances indicates expected stability for the B5H5—2 ion, but not for the neutral molecule. A simplified method of accounting for the molecular orbitals in icosahedral B12H12—2 yields some conclusions concerning B11 hydrides and ions.