Which one of the following Ni(II) complexes is diamagnetic and has tet

Which one of the following Ni(II) complexes is diamagnetic and has tetrahedral geometry ?

²⁻” option2=”[Ni(CO)₄]” option3=”[Ni(NH₃)₄]²⁺” option4=”[Ni(CN)₄]²⁻” correct=”option2″]

Among the given options, [Ni(CO)₄] is both diamagnetic and has tetrahedral geometry.

[Ni(CO)₄]: In this complex, Nickel is in the 0 oxidation state (Ni(0)). Its electron configuration is d¹⁰. All 10 d electrons are paired. The hybridization is sp³, resulting in a tetrahedral geometry. Since all electrons are paired, the complex is diamagnetic.
For Ni(II) complexes (d⁸):
– [NiCl₄]²⁻: Cl⁻ is a weak field ligand. Forms a tetrahedral complex (sp³ hybridization) which is paramagnetic (2 unpaired electrons).
– [Ni(NH₃)₄]²⁺: NH₃ is a moderate field ligand. Can form tetrahedral (sp³, paramagnetic) or square planar (dsp², diamagnetic) complexes depending on conditions, but the tetrahedral form is paramagnetic.
– [Ni(CN)₄]²⁻: CN⁻ is a strong field ligand. Forms a square planar complex (dsp² hybridization) which is diamagnetic (all electrons paired).

The question specifically asks for a Ni(II) complex that is diamagnetic and tetrahedral. Based on standard crystal field and valence bond theories, Ni(II) (d⁸) tetrahedral complexes are typically paramagnetic, while diamagnetic Ni(II) complexes are typically square planar. Therefore, none of the Ni(II) options (A, C, D) are both diamagnetic and tetrahedral. However, option B, [Ni(CO)₄], is tetrahedral and diamagnetic, fitting these two criteria perfectly, although it is a Ni(0) complex. This suggests a likely error in the question’s specification of “Ni(II) complexes”, and that option B was the intended answer despite this discrepancy. As per the provided options, B is the only complex listed that possesses both tetrahedral geometry and diamagnetic character.