Structures of selected boranes and carboranes

Nido‐pentaborane(9) (B₅H₉), 1, nido‐2,3‐diethyl‐2,3‐dicarbahexaborane(8) [(C₂H₅)₂C₂B₄H₆], 2, nido‐decaborane(14) (B₁₀H₁₄), 3, closo‐1,2‐dicarbadodecaborane(12) (H₂C₂B₁₀H₁₀), 4, can be used as possible source compounds for boron and boron carbide thin film deposition. Inner shell electron energy‐loss spectroscopy (ISEELS) studies of the boron 1s and carbon 1s core excitations of gas phase species have been undertaken so as to characterize these molecular precursors at solid surfaces. The near edge structure of ISEELS provides a good ‘‘fingerprint’’ for the identification of these molecular species. A comparison is made between calculated [modified neglect of differential overlap (MNDO)] bond lengths for molecular clusters and the x‐ray or electron diffraction bond lengths, bond lengths determined from extended energy‐loss fine structure.