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A number of (hetero)boranes are known in which a main group atom <i>X</i> ‘bridges’ a B—B connectivity in the open face, and in such species <i>X</i> has previously been described as simply a bridge or, alternatively, as a vertex in a larger cluster. In this study we describe an approach to distinguish between these options based on identifying the best fit of the experimental {B<i>_x</i>} cluster fragment with alternate exemplar {B<i>_x</i>} fragments derived from DFT-optimized [B<i>_n</i>H<i>_n</i>]²⁻ models. In most of the examples studied atom <i>X</i> is found to be better regarded as a vertex, having ‘a ‘verticity’ of ca. 60–65%. Consideration of our results leads to the suggestion that the radial electron contribution from <i>X</i> to the overall skeletal electron count is more significant than the tangential contribution.