Page 180 - Nomenclature of Inorganic Chemistry (IUPAC Recommendations 2005)

IR-9.2 C O O R D I N A T I O N C O M P O U N D S

In the first name, the first place where the rhodium atoms can be identified as being
inequivalent is at the kappa term associated with the m-chlorido ligand. Thus, the chloride-
bridged rhodium atoms must b e a ssigned the central atom locants 1 a nd 2 ( although which is
which is not known a t t his stage), and the other rhodium atom must be assigned the locant 3.
The next difference in the name t hat relates to central atom 1 o r 2 is the diphenylphosphanyl
k term. Those portions of the ligand are bound to the end rhodium a toms and not to the
middle r hodium atom. Since one of the end rhodium atoms is already given the locant 3,
from the earlier difference, t he other r hodium atom must be assigned locant 1, and the
middle a tom is left w ith locant 2.
For the second n ame, the locant 3 i s a ssigned in the same way, but the middle R h a tom
should be assigned locant 1 as it now appears earlier in the ligand name ( in the k term for
phosphanediyl).

Example:

9. 1 −
Al
2 3
Al C Al

Si
4
m 4 -carbido-quadro-
3
3
2
1
2
1
(trialuminiumsilicon)ate(Al —Al )(Al —Al )(Al —Si)(Al —Si)(1 )
In this example the central atom locants are assigned as follows. Rule (a), above, results in
the silicon atom being assigned locant 4. The coordination numbers and ligand distribution
are the same for the three aluminium a toms, which only differ in which other c entral
atoms they are bonded to. The numbering of the aluminium atoms follows from rule (d)
above.
The prefix ‘cyclo’, italicized a nd cited before all ligands, m ay be used for monocyclic
compounds.

Example:
10. 3+
H N NH Me
3
2
Pd
3
HO OH
H N NH 3
3
Pt 1 2 Pt
O
H N H NH 3
3
2
2
cyclo-pentaammine-1k N,2k N,3kN-tri-m-hydroxido-
2
2
2
1:2k O;1:3k O;2:3k O-(methanamine-3kN)diplatinumpalladium(3þ)

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