`NiCl_(2) overset(KCN)to "complex"A`
`NiCl_(2) underset("excess") overset(KCl)to "complex"B`
A & B complexes have the co-ordination number 4.
The IUPAC name of complexes 'A' & 'B' are respectively :

Options

A. Potassium tetracyanonickelate(II) and Potassium tetrachloronickelate(II)
B. Potassium tetracyanonickel(II) and Potassium tetrachloronickel(II)
C. Potassium cyanonickelate(II) and Potassium chloronickelate(II)
D. Potassium cyanonickel(II) and Potassium chloronickel(II)

Answer

To find the IUPAC names of the complexes A and B formed from the reactions of NiCl₂ with KCN and KCl respectively, we can follow these steps:

### Step 1: Identify the Complexes Formed
1. **Complex A Formation**:
- Reaction: NiCl₂ + KCN → K₂[Ni(CN)₄] + 2 KCl
- Here, the complex formed is K₂[Ni(CN)₄], which indicates that nickel is coordinated with four cyanide ligands.

2. **Complex B Formation**:
- Reaction: NiCl₂ + KCl → K₂[NiCl₄]
- The complex formed here is K₂[NiCl₄], indicating that nickel is coordinated with four chloride ligands.

### Step 2: Determine the Coordination Number
Both complexes A and B have a coordination number of 4, as stated in the question.

### Step 3: Assign Ligands and Metal
1. **For Complex A**:
- Ligand: Cyanide (CN⁻), which is named as "cyano" in the IUPAC nomenclature.
- Metal: Nickel (Ni) with an oxidation state of +2.

2. **For Complex B**:
- Ligand: Chloride (Cl⁻), which is named as "chloro" in the IUPAC nomenclature.
- Metal: Nickel (Ni) with an oxidation state of +2.

### Step 4: Determine the Oxidation State of Nickel
1. **For Complex A**:
- Let the oxidation state of Ni be X.
- The overall charge of the complex is -2 (from K₂).
- Equation: X + 4(-1) = -2 → X - 4 = -2 → X = +2.

2. **For Complex B**:
- Let the oxidation state of Ni be Y.
- The overall charge of the complex is -2 (from K₂).
- Equation: Y + 4(-1) = -2 → Y - 4 = -2 → Y = +2.

### Step 5: Write the IUPAC Names
1. **Complex A**:
- Cation: Potassium (K⁺).
- Ligand: Tetra-cyano (since there are four cyanide ligands).
- Metal: Nickel with oxidation state +2 → Nickel(II).
- IUPAC Name: Potassium tetra-cyanonickelate(II).

2. **Complex B**:
- Cation: Potassium (K⁺).
- Ligand: Tetra-chloro (since there are four chloride ligands).
- Metal: Nickel with oxidation state +2 → Nickel(II).
- IUPAC Name: Potassium tetra-chloronickelate(II).

### Final Answer
The IUPAC names of complexes A and B are:
- Complex A: **Potassium tetra-cyanonickelate(II)**
- Complex B: **Potassium tetra-chloronickelate(II)**

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