Page 4 - 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

Examples:
1. Priority sequence: a4b4c4d
Priority number sequence: 1525354
a b
M SP-4-4

c d

a c
M SP-4-2

d b

a b
M SP-4-3

d c

2. 1 2
Cl NCMe
3 Pt 1
N Cl

(SP-4-1)-(acetonitrile)dichlorido(pyridine)platinum(II)

If there are two p ossibilities, as in Example 3, the configuration index is the priority
number with the higher n umerical value. Both the priority 2 l igand (acetonitrile) and the
priority 3 l igand (pyridine) are trans to a p riority 1 l igand (chloride). T he higher numerical
value (3) is chosen f or the configuration index. This choice is sometimes referred to as
having been made according to the principle of trans maximum difference, i.e. that the
difference between the numerical values of the priority numbers of the ligands should b e a s
large as possible.

Example:

3. 1 2
Cl NCMe
Pt
1 3
Cl N

(SP-4-3)-(acetonitrile)dichlorido(pyridine)platinum(II)

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