Inner-shell excitation of boranes and carboranes

Oscillator strengths for B 1s excitation of two borane cage compounds [nido-pentaborane(9) (B₅H₉) and nido-decaborane(14) (B₁₀H₁₄)] and for B 1s and C 1s excitation of three carborane cage compounds [closo-o-carborane (C₂B₁₀H₁₂), nido-2,3-diethyl-2,3-dicarbahexaborane [(C₂H₅)₂C₂B₄H ₆], and 1,2-dicarbaundecaborane-(11) (C₂B₉H₁₁)] have been derived from inner-shell electron energy loss spectra (ISEELS), recorded under electric dipole scattering conditions. The spectral features have been assigned on the basis of spectral comparisons and of the results of semiempirical (MNDO and extended Hückel) molecular orbital calculations. The 1,2-dicarbaundecaborane species was generated in situ by thermal decomposition of the bis(nido-1,2-dicarbaundecaborane)nickel species. The preservation of the nido form of the ligand after decomposition is deduced from the experimental B 1s and C 1s spectra.