IUPAC Nomenclature — Revision Notes

⚡ 30-Second Revision

Cation first, then anion.
Ligands before metal — in coordination sphere.
Ligands alphabetical order — (ignore prefixes).
Anionic ligands: — end in '-o' (e.g., chloro, hydroxo).
Neutral ligands: — aqua ($\text{H}_2\text{O}$), ammine ($\text{NH}_3$), carbonyl ($\text{CO}$), nitrosyl ($\text{NO}$), others by common name.
Prefixes: — di-, tri-, tetra- for simple ligands; bis-, tris-, tetrakis- for complex ligands (in parentheses).
Metal name: — Unchanged for cationic/neutral complexes; '-ate' suffix for anionic complexes (e.g., ferrate, cuprate).
Oxidation state: — Roman numeral in parentheses after metal (e.g., (II), (III)).
Ambidentate: — Specify donor atom (e.g., nitro vs. nitrito-O).
Bridging: — '$\mu$-' prefix.

2-Minute Revision

IUPAC nomenclature for coordination compounds follows a strict set of rules to ensure unique naming. Always start by naming the cation, followed by the anion. Within the coordination sphere, ligands are named first, in alphabetical order, ignoring any numerical prefixes like 'di-' or 'tri-'.

Anionic ligands typically end in '-o' (e.g., chloro, cyano), while neutral ligands have specific names like 'aqua' for water and 'ammine' for ammonia. Use simple prefixes (di, tri) for simple ligands and complex prefixes (bis, tris) for ligands whose names already contain numbers or are complex organic molecules, enclosing the ligand name in parentheses.

The central metal's name remains unchanged if the complex is cationic or neutral, but an '-ate' suffix is added if the complex is anionic (e.g., ferrate, platinate). Finally, the oxidation state of the central metal is indicated by Roman numerals in parentheses immediately after the metal's name.

Remember to correctly calculate the oxidation state by considering all ligand charges and the overall complex charge. For ambidentate ligands, specify the bonding atom.

5-Minute Revision

A quick mastery of IUPAC nomenclature for coordination compounds is crucial for NEET. The process is systematic: First, identify the cation and anion of the entire compound and name the cation first. For example, in $\text{K}_4[\text{Fe}(\text{CN})_6]$, 'Potassium' is the cation.

Next, focus on the coordination sphere (the part in square brackets). Identify all ligands and the central metal. Ligands are named before the metal. If there are multiple different ligands, arrange them alphabetically, but remember to ignore numerical prefixes (like 'di-', 'tri-') when determining this order.

For instance, 'ammine' comes before 'chloro', even if it's 'diammine'.

Ligand naming depends on its charge: anionic ligands end in '-o' (e.g., $\text{Cl}^-$ is chloro, $\text{OH}^-$ is hydroxo). Neutral ligands have specific names (e.g., $\text{H}_2\text{O}$ is aqua, $\text{NH}_3$ is ammine, $\text{CO}$ is carbonyl).

For the number of ligands, use 'di-, tri-, tetra-' for simple ligands (e.g., dichloro), but 'bis-, tris-, tetrakis-' for complex ligands or those already containing numerical prefixes in their names (e.

g., bis(ethylenediamine)). Always enclose the complex ligand name in parentheses.

Now, for the central metal: If the coordination sphere is cationic or neutral, the metal's name is used as is (e.g., cobalt, platinum). If the coordination sphere is anionic, add the suffix '-ate' to the metal's name (e.

g., cobaltate, platinate). For some metals, use their Latin roots (e.g., iron $\rightarrow$ ferrate, copper $\rightarrow$ cuprate). Finally, calculate the oxidation state of the central metal. This is done by summing the known charges of all ligands and equating it to the overall charge of the coordination sphere.

Indicate this oxidation state with Roman numerals in parentheses immediately after the metal's name (e.g., (II), (III)).

Example: Name $[\text{Cr}(\text{NH}_3)_3\text{Cl}_3]$.

1
Neutral complex.
2
Ligands: Ammine ($\text{NH}_3$, neutral), Chloro ($\text{Cl}^-$, -1 charge). Three of each.
3
Alphabetical order: Ammine before Chloro. So, triammine, trichloro.
4
Metal: Chromium (Cr). Neutral complex, so no '-ate'.
5
Oxidation state: $x + 3(0) + 3(-1) = 0 \Rightarrow x - 3 = 0 \Rightarrow x = +3$. So, (III).
6
Name: Triamminetrichlorochromium(III).

Prelims Revision Notes

For NEET, IUPAC nomenclature of coordination compounds is a high-scoring topic. Focus on these factual recalls and rules:

1
Overall Compound Naming: — Cation is always named first, followed by the anion. If the complex is the cation, it's named first. If the complex is the anion, the counter cation is named first.
2
Ligand Naming:

* Anionic Ligands: End in '-o'. Examples: $\text{F}^-$ (fluoro), $\text{Cl}^-$ (chloro), $\text{Br}^-$ (bromo), $\text{I}^-$ (iodo), $\text{CN}^-$ (cyano), $\text{OH}^-$ (hydroxo), $\text{O}^{2-}$ (oxo), $\text{S}^{2-}$ (thio), $\text{CO}_3^{2-}$ (carbonato), $\text{C}_2\text{O}_4^{2-}$ (oxalato), $\text{SO}_4^{2-}$ (sulfato).

* Neutral Ligands: Specific names: $\text{H}_2\text{O}$ (aqua), $\text{NH}_3$ (ammine), $\text{CO}$ (carbonyl), $\text{NO}$ (nitrosyl). Others often retain common names (e.g., pyridine, phosphine).

* Cationic Ligands: Rare, end in '-ium' (e.g., hydrazinium).

1
Ligand Order: — Alphabetical order of ligand names. Ignore numerical prefixes (di, tri, bis, tris) when determining alphabetical order.
2
Numerical Prefixes for Ligands:

* Simple ligands: di-, tri-, tetra-, penta-, hexa- (for 2, 3, 4, 5, 6 ligands). * Complex ligands (or those with numerical prefixes in their names, e.g., ethylenediamine): bis-, tris-, tetrakis- (for 2, 3, 4 ligands). Ligand name is enclosed in parentheses.

1
Central Metal Naming:

* Cationic or Neutral Complex: Metal name as is (e.g., cobalt, nickel, platinum). * Anionic Complex: Metal name + '-ate' suffix. Latin roots for some: Fe (ferrate), Cu (cuprate), Ag (argentate), Au (aurate), Pb (plumbate), Sn (stannate).

1
Oxidation State: — Roman numeral in parentheses immediately after the metal's name. Calculated by: (Metal oxidation state) + (Sum of ligand charges) = (Overall complex charge).
2
Ambidentate Ligands: — Specify the donor atom. E.g., $\text{NO}_2^-$ can be nitro (N-bonded) or nitrito-O (O-bonded). $\text{SCN}^-$ can be thiocyanato (S-bonded) or isothiocyanato (N-bonded).
3
Bridging Ligands: — Indicated by '$\mu$-' prefix before the ligand name.

Vyyuha Quick Recall

Let's Always Put Metal's Oxidation State:

Ligands first (alphabetical, ignore prefixes)
Anionic ligands end in '-o'
Prefixes: di/tri for simple, bis/tris for complex (in parentheses)
Metal name: normal for cation/neutral, '-ate' for anion
Oxidation state (Roman numeral)
Stereochemistry (if applicable, less common for NEET basic nomenclature)