Page 99 - Nomenclature of Inorganic Chemistry (IUPAC Recommendations 2005)

S U B S T I T U T I V E N O M E N C L A T U R E IR-6.2

and hydrocarbon nomenclature is that the number of hydrogen atoms must b e d efined; it
cannot be inferred from simple bonding considerations. The number of hydrogen atoms is
indicated by the appropriate arabic numeral in parentheses directly following the name. Such
names convey only compositional information.

Examples:

1. B 2 H 6 diborane(6)
icosaborane(16)
2. B 20 H 16
IR-6.2.3.2 Structural descriptor names

More structural i nformation is obtained by augmenting the stoichiometric name by a
2
structural d escriptor. The descriptor is based on electron-counting relationships and is
presented in Table IR-6.2.

Table IR-6.2 Summary of common polyboron hydride structure types according to stoichiometry and
electron-counting relationships a

Descriptor Skeletal Parent Description of structure
electron hydride
pairs

closo nþ1 B n H nþ2 Closed polyhedral structure with triangular faces only.
nido nþ2 B n H nþ4 Nest-like non-closed polyhedral structure; n vertices of
the parent (nþ1)-atom closo polyhedron occupied.
arachno nþ3 B n H nþ6 Web-like non-closed polyhedral structure; n vertices of
the parent (nþ2)-atom closo polyhedron occupied.
hypho nþ4 B n H nþ8 Net-like non-closed polyhedral structure; n vertices of
the parent (nþ3)-atom closo polyhedron occupied.
klado nþ5 B n H nþ10 Open branch-like polyhedral structure; n vertices of the
parent (nþ4)-atom closo polyhedron occupied.
a 3
The structural relationships are often represented by a R udolph diagram.

Examples:

1.

1

5 2

4 3

nido-pentaborane(9), B 5 H 9

90