SL-4-i where B 1 and B i are "co-spatial" as are the remaining two B-atoms with an overall linear geometry; i ∈ {2, 3, 4}. Examples of the implementation of these nomenclatural rules are given in the Supplementary Information. We reiterate: these additional polytope configuration symbols are currently not intended for chemical nomenclature. This journal is © The Royal Society of Chemistry 20xx