What is the IUPAC name of [Pt(NH3)2Cl(NO2)]?
Diamminechloridonitrito-N-platinum(II)
Determining the IUPAC Name of Coordination Complexes
The question asks for the IUPAC name of the coordination complex [Pt(NH3)2Cl(NO2)]. To name a coordination complex according to IUPAC guidelines, we follow a set of rules:
- Identify the ligands and the central metal atom.
- Determine the charge of the ligands and the coordination sphere.
- Calculate the oxidation state of the central metal atom.
- Name the ligands. Anionic ligands end in '-o' (e.g., chloride becomes chlorido). Neutral ligands are usually named as they are (e.g., NH3 is ammine), with a few exceptions. Ambidentate ligands are indicated by specifying the atom through which they are coordinated (e.g., nitrito-N for coordination via nitrogen, nitrito-O for coordination via oxygen).
- List the ligands in alphabetical order before the name of the central metal atom. Prefixes (di, tri, tetra, etc.) indicate the number of each simple ligand.
- Name the central metal atom. If the coordination sphere is neutral or cationic, the metal name is used directly. If the coordination sphere is anionic, the metal name ends in '-ate'.
- Write the oxidation state of the metal in Roman numerals in parentheses after the metal name.
Analyzing the Complex [Pt(NH3)2Cl(NO2)]
Let's apply these rules to the given complex:
- Central Metal: Platinum (Pt)
- Ligands:
- NH3: Ammine (neutral ligand, charge = 0). There are two of them.
- Cl: Chloride (anionic ligand, charge = -1). There is one of them. According to IUPAC rules, this is named 'chlorido'.
- NO2: Nitrito (anionic ligand, charge = -1). There is one of them. This is an ambidentate ligand. It can coordinate via nitrogen (nitrito-N) or oxygen (nitrito-O). Without further information, 'nitrito-N' is a common mode of coordination, and we will consider this based on the available options.
Calculating the Oxidation State of Platinum
The complex [Pt(NH3)2Cl(NO2)] is neutral, meaning the sum of the charges of the metal and all ligands is zero.
Let the oxidation state of Platinum be \(x\).
Charge of complex = (Charge of Pt) + (Number of NH3 × Charge of NH3) + (Number of Cl × Charge of Cl) + (Number of NO2 × Charge of NO2)
\(0 = x + (2 \times 0) + (1 \times -1) + (1 \times -1)\)
\(0 = x + 0 - 1 - 1\)
\(0 = x - 2\)
\(x = +2\)
The oxidation state of Platinum is +2, which will be denoted as (II) in the name.
Ordering the Ligands Alphabetically
The ligands are ammine (a), chlorido (c), and nitrito-N (n).
In alphabetical order, they are ammine, chlorido, nitrito-N.
- Ammine: There are two, so 'diammine'.
- Chlorido: There is one, so 'chlorido'.
- Nitrito-N: There is one, so 'nitrito-N'.
Assembling the IUPAC Name
Combine the ligand names in alphabetical order, followed by the metal name and its oxidation state.
Ligands: diammine, chlorido, nitrito-N
Metal: platinum
Oxidation state: (II)
Putting it together: diamminechloridonitrito-N-platinum(II)
Evaluating the Options
Let's compare our derived name with the given options:
- Option 1: Diamminechloridenitrito-N-platinum(II). Incorrect because 'chloride' should be 'chlorido' as an anionic ligand.
- Option 2: Diamminechloridonitrito-N-platinum(II). Matches our derived name.
- Option 3: Diamminechloridonitrito-O-platinum(II). This name implies coordination via oxygen (nitrito-O). While possible, 'nitrito-N' is also possible, and Option 2 matches our general assumption and appears as a choice.
- Option 4: Diammonia chloridonitrito-N-platinum(II). Incorrect because the neutral ligand NH3 is named 'ammine', not 'ammonia'.
Based on the systematic application of IUPAC rules and evaluation of options, the correct IUPAC name is Diamminechloridonitrito-N-platinum(II).
| Component | Name | Charge | Number |
|---|---|---|---|
| Pt | Platinum | +2 | 1 |
| NH3 | Ammine | 0 | 2 |
| Cl | Chlorido | -1 | 1 |
| NO2 | Nitrito-N | -1 | 1 |
Revision Table: Key IUPAC Naming Rules for Complexes
| Rule Aspect | Description | Example |
|---|---|---|
| Ligand Naming (Anionic) | End in '-o' | Cl<sup>-</sup> → chlorido, CN<sup>-</sup> → cyano |
| Ligand Naming (Neutral) | Usually unchanged (exceptions like aqua, ammine) | NH<sub>3</sub> → ammine, H<sub>2</sub>O → aqua |
| Ligand Naming (Ambidentate) | Specify coordinating atom | -NO<sub>2</sub> → nitrito-N (via N), nitrito-O (via O) |
| Ligand Order | Alphabetical order by ligand name | Ammine comes before chlorido |
| Prefixes | di-, tri-, tetra- for simple ligands; bis-, tris-, tetrakis- for complex ligands | (NH<sub>3</sub>)<sub>2</sub> → diammine |
| Metal Name (Neutral/Cationic Complex) | Direct metal name | Platinum |
| Metal Name (Anionic Complex) | Metal name ends in '-ate' | Platinum → platinate |
| Oxidation State | In Roman numerals in parentheses after metal name | Platinum(II) |
Additional Information on Coordination Compounds and IUPAC Naming
Coordination compounds, also known as coordination complexes, consist of a central metal atom or ion surrounded by a set of ligands. Ligands are molecules or ions that donate electrons to the central metal atom, forming coordinate covalent bonds.
The rules for naming coordination complexes are standardized by the International Union of Pure and Applied Chemistry (IUPAC) to ensure clarity and consistency in chemical nomenclature. These rules help distinguish between different isomers and compounds with varying compositions and structures.
Ambidentate ligands, like the nitrito group (NO2<sup>-</sup>), cyanide (CN<sup>-</sup>), and thiocyanate (SCN<sup>-</sup>), can coordinate through different donor atoms. The IUPAC name specifies the donor atom using suffixes or prefixes, such as -N or -O for nitrito, -C or -N for cyano, and -S or -N for thiocyanato (or isothiocyanato).
Understanding the charge of ligands and the overall complex is crucial for correctly determining the oxidation state of the central metal, which is an essential part of the IUPAC name.
Common neutral ligands with special names include:
- H2O: aqua
- NH3: ammine
- CO: carbonyl
- NO: nitrosyl
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