14-Vertex Heteroboranes with 14 Skeletal Electron Pairs: An Experimental and Computational Study

Three isomers of [(Cp*Ru)₂C₂B₁₀H₁₂], the first examples of 14-vertex heteroboranes containing 14-skeletal electron pairs, have been synthesized by the direct electrophilic insertion of a {Cp*Ru⁺} fragment into the anion [4-Cp*-4,1,6-RuC₂B₁₀H₁₂]⁻. All three compounds have the same unique polyhedral structure having an approximate C_ssymmetry and featuring a four-atom trapezoidal face. X-ray diffraction studies could confidently identify only one of the two cage C atoms in each structure. The other C atom position has been established by a combination of i) best fitting of computed and experimental¹¹B and¹H NMR chemical shifts, and ii) consideration of the lowest computed energy for series of isomers studied by DFT calculations. In all three isomers, one cage C atom occupies a degree-4 vertex on the short parallel edge of the trapezium.