Heteroboranes are classes of boranes, at least one boron atom is replaced by another element. Like many of the related boranes, these clusters are polyhedra and are similarly classified as closo-, nido-, arachno-, hypho-, etc. based on whether they represent a complete (closo-) polyhedron, or a polyhedron that is missing one (nido-), two (arachno-), or more vertices.
Heteroboranes can be classified by converting the heteroatom to a BHx group that has the same number of electrons.
References
Heteroborane Wikipedia(Text) CC BY-SA