Cluster types Boranes

b6h10 typical example. geometry is, in essence, 7-boron framework (pentagonal bipyramid), missing vertex had highest number of near neighbours, e.g., vertex 5 neighbours. hydrogen atoms bridge around open face. notable exception general scheme of b8h12, expected have nido- geometry (based on b9h9 missing 1 vertex), similar in geometry b8h14, based on b10h10. according these convensions, diborane simplest nido- borane, 2-boron framework can considered simplest deltahedron, triangular dihedron or equilateral triangle, 1 vertex removed. however, structural descriptor redundant in case, structure of diborane unambiguous.

the names series of boranes derived general scheme cluster geometries:-

hypercloso- (from greek on cage ) closed complete cluster, e.g., b8cl8 distorted dodecahedron.
closo- (from greek cage ) closed deltahedron cluster, 2n+2 framework electrons e.g., icosahedral b12h12
nido- (from latin nest ) b occupies n vertices of n+1 deltahedron 2n+4 framework electrons, e.g., b5h9 octahedron missing 1 vertex
arachno- (from greek spiders web ) b occupies n vertices of n+3 deltahedron 2n+6 framework electrons e.g. b4h10 octahedron missing 2 vertices
hypho- (from greek net ) b occupies n vertices of n+2 deltahedron, e.g., b8h16 trigonal prismatic
klado- (from greek branch )
conjuncto- 2 or more of above fused together, e.g., edge or 2 vertex fused b19h22, face or 3 vertex fused b21h18, , 4 vertex fused b20h16