Page 6 - Nomenclature of Inorganic Chemistry (IUPAC Recommendations 2005)

IR-9.3 C O O R D I N A T I O N C O M P O U N D S

2. 1
1 NO 2 2
O N NH 3
2
2 Co 1
H N NO 2
3
NH 3
2

mer-[Co(NH 3 ) 3 (NO 2 ) 3 ]
3
(OC-6-21)-triamminetrinitrito-k N-cobalt(III)

3. 1
2 NO 2 1
H N NO 2
3
2 Co 1
H N NO 2
3
NH 3
2
fac-[Co(NH 3 ) 3 (NO 2 ) 3 ]
3
(OC-6-22)-triamminetrinitrito-k N-cobalt(III)

4. 1 +
AsPh
2 3 4
ON CO
Cr
MeCN NCMe
3 C 3
O
4
(OC-6-43)-bis(acetonitrile)dicarbonylnitrosyl(triphenylarsane)chromium(1þ)

IR-9.3.3.5 Square pyramidal coordination systems (SPY-4, S PY-5)
The configuration index o f a n SPY-5 s ystem consists of two digits. The first digit is
the priority number of the ligating atom on the C 4 symmetry axis (the reference axis) of the
idealized p yramid. The second digit i s t he priority number of the ligating atom trans to the
ligating atom with the lowest priority number in the plane p erpendicular to the C 4 symmetry
axis. If there i s m ore than one such atom in the perpendicular p lane, then the second d igit is
chosen t o h ave the highest numerical value.
The configuration index of an SPY-4 s ystem is a s ingle digit that is chosen i n t he same
way as the second digit of SPY-5 s ystems. The configuration index o f a four-coordinate
square pyramidal system will therefore be the same a s t hat for the square p lanar structure
that would r esult from the ligands and the central atom being coplanar. T he difference
between t he structures is described by the polyhedral symbol rather than by the configuration
index.

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