STRUCTURE AND STABILITY OF HYDROGEN POOR CLOSO-${\rm B}_{n}{\rm H}_{n-x}^{-/0/+}$ (n = 5 - 12)

Structures and stabilities of hydrogen poor closo-${\rm B}_{n}{\rm H}_{n-1}^{-}$, closo-BnHn-2, and closo-${\rm B}_{n}{\rm H}_{n-3}^{+}$ (n = 5 - 12) have been investigated at the B3LYP/6-311+G** density functional level of theory. It is found that ${\rm B}_{5}{\rm H}_{4}^{-}$, B5H3, ${\rm B}_{5}{\rm H}_{2}^{+}$, and ${\rm B}_{6}{\rm H}_{3}^{+}$ have open instead of the expected closo structures, and the other isomers have the same structural pattern as closo-${\rm B}_{n}{\rm H}_{n}^{2-}$. Energetic analysis identifies closo-${\rm B}_{n}{\rm H}_{n-1}^{-}$ (n = 7, 9), closo-BnHn-2 (n = 7, 11), and closo-${\rm B}_{n}{\rm H}_{n-3}^{+}$ (n = 6, 8, 10) as the most stable clusters. The CO affinities of the most stable closo-BnHn-1CO-, closo-BnHn-2(CO)2, and closo-${\rm B}_{n}{\rm H}_{n-3}({\rm CO})_{3}^{+}$ (n = 5 - 12) have been computed.