Answer the question on basis of passage given below:

Transition metals form a large number of complexes or coordination compounds in which the metal atoms are bound to a number of anions or neutral molecules. The valence bond theory explain the formation, magnetic behaviour and geometrical shapes while the crystal field theory explains the effect of different crystal fields on the degeneracy of d-orbitals energies of the central metal atom/ion. This provides for the quantitative estimation of orbital separation energies, magnetic moments and spectral and stability parameters.

Which of the following complexes are not correctly matched with hybridization of their central metal ion?

\([MnCl_4]^{2-} : dsp^2\)

The correct answer is option 4. \([MnCl_4]^{2-} : dsp^2\).

The issue lies with the electron configuration and hybridization of the central metal ions.

1. Nickel (Ni) in \([Ni(H_2O)_6]^{2+}\): It has an electronic configuration of \([_{18}Ar] 3d^8\). Water is a weak field ligand, so minimal pairing of d-electrons occurs. To form six bonds with the water ligands, \(Ni\) undergoes \(sp^3d^2\) hybridization. So, the given hybridization is correct.
2. Cobalt (Co) in \([CoF_6]^{3-}\): Cobalt has the configuration \([_{18}Ar] 3d^7\). Fluoride \((F^-)\) is a weak field ligand, so minimal pairing happens. Here, \(sp^3d^2\) hybridization is likely for bonding with six fluorides. So, the given hybridization is correct.
3. Copper (Cu) in \([Cu(NH_3)_4]^{3+}\): Copper has the configuration \([_{18}Ar] 3d^9\). Ammonia \((NH_3)\) acts as a weak field ligand. To form four bonds, Cu undergoes \(dsp^2\) hybridization. So, the given hybridization is correct.
4. Manganese (Mn) in \([MnCl_4]^{2-}\): Manganese has the configuration \([_{18}Ar] 3d^5\). Chloride \((Cl^-)\) is a weak field ligand. However, \(Mn\) has five \(3d\) electrons, and for four bonds, only \(dsp^3\) hybridization is needed. Here, \(dsp^2\) hybridization wouldn't be ideal. So, the given hybridization is incorrect.

Therefore, the complex that is NOT correctly matched with its hybridization is (4) \([MnCl_4]^{2-} : dsp^2\). The correct hybridization for Mn in this complex is \(dsp^3\).