Complex compounds are molecular compounds which retain their identities even when dissolved in water. They do not give all the simple ions in solution but instead furnish complex ions. The complex compounds are often called coordination compounds because certain groups called ligands are attached to the central metal ion by coordinate or dative bonds. coordination compounds exhibit isomerism, both structural and stereoisomerism. the structure, magnetic property, colour and electrical properties of complexes are explained by various theories:
Q. In which of the following pairs, both the complexes have the same geometry?

Options

A. `[NiCl_(4)]^(2-),[Ni(CN)_(4)]^(2-)`
B. `[CoF_(6)]^(3-),[Co(NH_(3))_(6)]^(3+)`
C. `[Ni(CO)_(4)],{Ni(CN)_(4)]^(2-)`
D. `[Cu(NH_(3))_(4)]^(+),[Ni(NH_(3))_(4)]^(2+)`

Answer

To solve the question about which pairs of complexes have the same geometry, we need to analyze the coordination compounds mentioned in the question.

### Step-by-Step Solution:

1. **Identify the Coordination Compounds**:
We need to analyze the geometry of the following pairs of complexes:
- NiCl4 and Ni(CN)4^2-
- CoF6^3- and Co(NH3)6^3+
- Ni(CO)4 and Ni(CN)4^2-
- Cu(NH3)4^+ and Ni(NH3)4^2+

2. **Determine the Oxidation States**:
- For NiCl4: Nickel is in +2 oxidation state (since Cl is -1, total -4 from 4 Cl).
- For Ni(CN)4^2-: Nickel is in +2 oxidation state (since CN is -1, total -4 from 4 CN).
- For CoF6^3-: Cobalt is in +3 oxidation state (since F is -1, total -6 from 6 F).
- For Co(NH3)6^3+: Cobalt is in +3 oxidation state (NH3 is neutral).
- For Ni(CO)4: Nickel is in 0 oxidation state (CO is neutral).
- For Ni(CN)4^2-: Nickel is in +2 oxidation state.
- For Cu(NH3)4^+: Copper is in +1 oxidation state (NH3 is neutral).
- For Ni(NH3)4^2+: Nickel is in +2 oxidation state.

3. **Analyze the Ligands**:
- Cl^- is a weak field ligand.
- CN^- and CO are strong field ligands.
- NH3 is a neutral ligand and can act as a weak or strong field ligand depending on the oxidation state of the metal.

4. **Determine the Hybridization**:
- For NiCl4: sp3 hybridization (tetrahedral geometry).
- For Ni(CN)4^2-: dsp2 hybridization (square planar geometry).
- For CoF6^3-: sp3d2 hybridization (octahedral geometry).
- For Co(NH3)6^3+: sp3d2 hybridization (octahedral geometry).
- For Ni(CO)4: sp3 hybridization (tetrahedral geometry).
- For Ni(CN)4^2-: dsp2 hybridization (square planar geometry).
- For Cu(NH3)4^+: sp3 hybridization (tetrahedral geometry).
- For Ni(NH3)4^2+: sp3 hybridization (tetrahedral geometry).

5. **Compare the Geometries**:
- NiCl4 (tetrahedral) vs. Ni(CN)4^2- (square planar) → Different geometries.
- CoF6^3- (octahedral) vs. Co(NH3)6^3+ (octahedral) → Same geometry.
- Ni(CO)4 (tetrahedral) vs. Ni(CN)4^2- (square planar) → Different geometries.
- Cu(NH3)4^+ (tetrahedral) vs. Ni(NH3)4^2+ (tetrahedral) → Same geometry.

6. **Conclusion**:
The pairs that have the same geometry are:
- CoF6^3- and Co(NH3)6^3+ (both octahedral).
- Cu(NH3)4^+ and Ni(NH3)4^2+ (both tetrahedral).

### Final Answer:
The pairs that have the same geometry are **CoF6^3- and Co(NH3)6^3+** and **Cu(NH3)4^+ and Ni(NH3)4^2+**.