Red_Book_2005

IR-2.2
(a) To enclose formulae for groups of atoms (the groups may be ions, substituent groups,
ligands or molecules), to avoid ambiguity or when the group is being multiplied. In the
latter case, amultiplicative subscript numeral follows the closing parenthesis. In the case of
common ions such as nitrate and sulfate, parentheses are recommended but not mandatory.
Examples:
1. Ca3 (PO4 ) 2
2. [Te(N3 ) 6 ]
3. (NO3 ) or NO3
4. [FeH(H 2 )(Ph 2 PCH 2 CH 2 PPh 2 ) 2 ] þ
5. PH(O)(OH) 2
6. [Co(NH3 ) 5 (ONO)][PF6 ] 2
(b) To enclose the abbreviation of a ligand name in formulae. (Recommended ligand
abbreviations are given inTables VII and VIII. See also Sections IR-4.4.4 and IR-9.2.3.4.)
Example:
3 þ
7. [Co(en)3 ]
(c) To enclose the superscripted radical dot and its multiplier for polyradicals, in order to
avoid ambiguity in relation to multiplying the charge symbol.
Example:
(2* )
8. NO
(d) In solid-state chemistry, to enclose symbols of atoms occupying the same type of site in
arandom fashion. The symbols themselves are separated by acomma, with no space.
Example:
9. K(Br,Cl)
(e) In solid-state chemistry, to indicate an atom or agroup of atoms in atetrahedral site.
Example:
10. (Mg)[Cr2 ]O4
(f) To indicate the composition of anon-stoichiometric compound.
Examples:
11. Fe3 x Li4-x Ti2(1-x ) O 6 ( x ¼ 0.35)
12. LaNi5 H x (05 x 5 66.7)
GRAMMAR
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