Ni(CO)₄ — Nickel Tetracarbonyl — is an important organometallic compound discussed in Class 12 Chemistry (Coordination Compounds and d-block elements).
Ni(CO)₄ is extremely toxic and was discovered by Ludwig Mond in 1890. The Mond process uses Ni(CO)₄ to purify nickel metal industrially.
Step 1: Ni in Ni(CO)₄ is in zero oxidation state (CO is a neutral ligand).
Step 2: Electronic configuration of Ni (Z=28): [Ar] 3d⁸ 4s²
Ni⁰: [Ar] 3d⁸ 4s²
Step 3: CO is a strong field ligand — it causes pairing of electrons. Under CO's influence: Ni⁰ rearranges to [Ar] 3d¹⁰ 4s⁰
Step 4: The 4s and three 4p orbitals hybridise → sp³ hybridisation
Result: 4 CO ligands occupy the 4 tetrahedral positions. All 3d electrons are now paired → diamagnetic
| Property | Ni(CO)₄ | [Ni(CN)₄]²⁻ |
|---|---|---|
| Oxidation state of Ni | 0 | +2 |
| Hybridisation | sp³ | dsp² |
| Geometry | Tetrahedral | Square planar |
| Magnetic nature | Diamagnetic | Diamagnetic |
Because Ni is in zero oxidation state with a full 3d¹⁰ configuration. The d orbitals are completely filled and unavailable for hybridisation. So only 4s and 4p orbitals hybridise to give sp³.
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