Past exam of the chemistry course of the year 4 of the natural sciences course of the University of Cambridge / 2022 / Paper 2 / Section H / 33 / d / ii

Use the neutral-fragment skeletal count: each AlMe supplies two electrons, each CEt supplies three and the bridging H supplies one. HenceThere are 13 nonhydrogen skeletal vertices, eight Al plus five C, and $16=n+3$ pairs. In the usual PSEP classification this is therefore arachno, corresponding to a 15-vertex closo parent with two vertices absent. The μ${}_4$-H cap contributes an electron but is not counted as a carbon-like skeletal vertex. The aluminium cube is a convenient subframework; its eight corners alone are not the complete Wade skeleton. Calculations on capped cubic carbaalanes likewise identify 16 skeletal pairs for the five-carbon-cap/one-hydride-cap case.^[ref]