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5
No numerical subscript should follow the square bracket used in this context. For example,
where the molecular formula is double the empirical formula, this should be indicated
inside the square bracket.
Example:
4.
Cl
H 2 C
H 2 C
Pt
IUPAC Provisional Recommendations
Cl
Cl
[{Pt(η 2 -C 2 H 4 )Cl(µ-Cl)} 2 ] is more informative than [Pt 2 (η 2 -C 2 H 4 ) 2 Cl 4 ]; the
representation [Pt(η 2 -C 2 H 4 )Cl 2 ] 2 is incorrect.
(b) To enclose the coordination entity of a charged (formal) coordination compound. In
this case, the superscript showing the charge appears outside the square bracket as do any
subscripts indicating the number of ions in the salt.
Examples:
5. [BH 4 ] _
6. [Al(OH)(OH 2 ) 5 ] 2+
7. [Pt(η 2 -C 2 H 4 )Cl 3 ] _
8. Ca[AgF 4 ] 2
9. [Co(NH 3 ) 5 (N 3 )]SO 4
10. [S 2 O 5 ] 2_
11. [PW 12 O 40 ] 3_
(c) In a salt comprising both cationic and anionic coordination entities, each ion is
separately enclosed in square brackets. (The cation is placed before the anion and no
individual charges are shown). Any subscripts indicating the number of complex ions in
the salt are shown outside the square brackets.
Examples:
12. [Co(NH 3 ) 6 ][Cr(CN) 6 ]
(comprising the ions [Co(NH 3 ) 6 ] 3+ and [Cr(CN) 6 ] 3_ )
13. [Co(NH 3 ) 6 ] 2 [Pt(CN) 4 ] 3
(comprising the ions [Co(NH 3 ) 6 ] 3+ and [Pt(CN) 4 ] 2_ )
Pt
CH 2
CH 2
Cl
Page 5 of 33 DRAFT 2 April 2004