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Naming Coordination Compounds: A Comprehensive Guide with Examples, Lecture notes of Chemistry

University of Isfahan (UI)Chemistry

it's about naming coordination compounds at inorganic chemistry

Typology: Lecture notes

2019/2020

Uploaded on 05/15/2020

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Naming Coordination Compounds
A complex is a substance in which a metal atom or ion is associated with a group of neutral
molecules or anions called ligands. Coordination compounds are neutral substances (i.e.
uncharged) in which at least one ion is present as a complex. You will learn more about
coordination compounds in the lab lectures of experiment 4 in this course.
The coordination compounds are named in the following way. (At the end of this tutorial we
have some examples to show you how coordination compounds are named.)
A. To name a coordination compound, no matter whether the complex ion is the cation or the
anion, always name the cation before the anion. (This is just like naming an ionic
compound.)
B. In naming the complex ion:
1. Name the ligands first, in alphabetical order, then the metal atom or
ion. Note: The metal atom or ion is written before the ligands in the
chemical formula.
2. The names of some common ligands are listed in Table 1.
�
For anionic ligands end in "-o"; for anions that end in "-ide"(e.g.
chloride), "-ate" (e.g. sulfate, nitrate), and "-ite" (e.g. nirite), change
the endings as follows: -ide -o; -ate -ato; -ite -ito
�
For neutral ligands, the common name of the molecule is used e.g.
H2NCH2CH2NH2 (ethylenediamine). Important exceptions: water is
called ‘aqua’, ammonia is called ‘ammine’, carbon monoxide is called
‘carbonyl’, and the N2 and O2 are called ‘dinitrogen’ and ‘dioxygen’.
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Naming Coordination Compounds

A complex is a substance in which a metal atom or ion is associated with a group of neutral molecules or anions called ligands. Coordination compounds are neutral substances (i.e. uncharged) in which at least one ion is present as a complex. You will learn more about coordination compounds in the lab lectures of experiment 4 in this course. The coordination compounds are named in the following way. (At the end of this tutorial we have some examples to show you how coordination compounds are named.) A. To name a coordination compound, no matter whether the complex ion is the cation or the anion, always name the cation before the anion. (This is just like naming an ionic compound.) B. In naming the complex ion:

  1. Name the ligands first, in alphabetical order, then the metal atom or ion. Note: The metal atom or ion is written before the ligands in the chemical formula.
  2. The names of some common ligands are listed in Table 1. �For anionic ligands end in "-o"; for anions that end in "-ide"(e.g. chloride), "-ate" (e.g. sulfate, nitrate), and "-ite" (e.g. nirite), change the endings as follows: -ide -o; -ate -ato; -ite -ito �For neutral ligands, the common name of the molecule is used e.g. H 2 NCH 2 CH 2 NH 2 (ethylenediamine). Important exceptions : water is called ‘aqua’, ammonia is called ‘ammine’, carbon monoxide is called ‘carbonyl’, and the N 2 and O 2 are called ‘dinitrogen’ and ‘dioxygen’.

Table 1. Names of Some Common Ligands Anionic Ligands Names Neutral Ligands Names Br-^ bromo NH 3 ammine F-^ fluoro H 2 O aqua O2-^ oxo NO Nitrosyl OH-^ Hydroxo CO Carbonyl CN-^ cyano O 2 dioxygen C 2 O 4 2-^ oxalato N 2 dinitrogen CO 3 2-^ carbonato C 5 H 5 N pyridine CH 3 COO-^ acetato H 2 NCH 2 CH 2 NH 2 ethylenediamine

3. Greek prefixes are used to designate the number of each type of ligand in the complex ion, e.g. di-, tri- and tetra-. If the ligand already contains a Greek prefix (e.g. ethylene di amine) or if it is polydentate ligands (ie. can attach at more than one binding site) the prefixes bis-, tris-, tetrakis-, pentakis-, are used instead. (See examples 3 and 4.) The numerical prefixes are listed in Table 2. Table 2. Numerical Prefixes Number Prefix Number Prefix Number Prefix

Silver Argenate Gold Aurate Tin Stannate

5. Following the name of the metal, the oxidation state of the metal in the complex is given as a Roman numeral in parentheses. C. To name a neutral complex molecule, follow the rules of naming a complex cation. Remember: Name the (possibly complex) cation BEFORE the (possibly complex) anion.See examples 7 and 8. For historic reasons, some coordination compounds are called by their common names. For example, Fe(CN) 63 ^ and Fe(CN) 64 ^ are named ferricyanide and ferrocyanide respectively, and Fe(CO) 5 is called iron carbonyl. Examples Give the systematic names for the following coordination compounds:

  1. [Cr(NH 3 ) 3 (H 2 O) 3 ]Cl 3 Answer: triamminetriaquachromium(III) chloride Solution: The complex ion is inside the parentheses, which is a cation. The ammine ligands are named before the aqua ligands according to alphabetical order. Since there are three chlorides binding with the complex ion, the charge on the complex ion must be +3 ( since the compound is electrically neutral). From the charge on the complex ion and the charge on the ligands, we can calculate the oxidation number of the metal. In this example, all the ligands are neutral molecules. Therefore, the oxidation number of chromium must be same as the charge of the complex ion, +3.
  2. [Pt(NH 3 ) 5 Cl]Br 3 Answer: pentaamminechloroplatinum(IV) bromide

Solution: The complex ion is a cation, the counter anion is the 3 bromides. The charge of the complex ion must be +3 since it bonds with 3 bromides. The NH 3 are neutral molecules while the chloride carries1 charge. Therefore, the oxidation number of platinum must be +4.

  1. [Pt(H 2 NCH 2 CH 2 NH 2 ) 2 Cl 2 ]Cl 2 Answer: dichlorobis(ethylenediamine)platinum(IV) chloride Solution: ethylenediamine is a bidentate ligand, the bis- prefix is used instead of di-
  2. [Co(H 2 NCH 2 CH 2 NH 2 ) 3 ] 2 (SO 4 ) 3 Answer: tris(ethylenediamine)cobalt(III) sulfate Solution: The sulfate is the counter anion in this molecule. Since it takes 3 sulfates to bond with two complex cations, the charge on each complex cation must be +3. Since ethylenediamine is a neutral molecule, the oxidation number of cobalt in the complex ion must be +3. Again, remember that you never have to indicate the number of cations and anions in the name of an ionic compound.
  3. K 4 [Fe(CN) 6 ] Answer: potassium hexacyanoferrate(II) Solution: potassium is the cation and the complex ion is the anion. Since there are 4 K+^ binding with a complex ion, the charge on the complex ion must be4. Since each ligand carries –1 charge, the oxidation number of Fe must be +2. The common name of this compound is potassium ferrocyanide.
  4. Na 2 [NiCl 4 ] Answer: sodium tetrachloronickelate(II) Solution: The complex ion is the anion so we have to add the suffix –ate in the name of the metal.
  5. Pt(NH 3 ) 2 Cl 4 Answer: diamminetetrachloroplatinum(IV)

**_2. (NH 4 ) 2 [CuCl 4 ]

  1. Na 3 [FeCl 1 (CN) 5 ]
  2. K 3 [CoF 6 ]
  3. pentaamminebromocobalt(III) sulfate
  4. hexaammineiron(III) hexacyanochromate (III)
  5. pentaamminesulfatocobalt(III) ion
  6. pentaaquahydroxoiron(III) ion_**