It is observed that [ ( η n − C 3 H 5 ) Mn ( CO ) 4 ] follows the E.A.N. r | TestHub

Passage / Comprehension

If two, three, four, or more atoms of the ligand are within bonding distance of the same metal atom, this is indicated by prefixing the name of the ligand with dihapto-, trihapto-, etc. (from the Greek for "fasten") or the symbol $η^{2}$ -, $η^{3}$ -, $η^{4}$ -, etc. ( $h^{2}$ -, $h^{3}$ -, $h^{4}$ -, etc. are also used). Thus, the formula of dibenzene chromium is written $(η^{6} - C_{6} H_{6})_{2} C r$ .

Alkyl and aryl groups which form only $σ$ bonds to metal atoms are monohapto groups. It should be noted that there are some differences in meaning between hapto- and -dentate as applied to ligands; hapticity refers to the number of ligand atoms bonded to the same metal atom (irrespective of the number of electrons involved); denticity refers to the number of donor bonds formed by the ligand.

It is observed that $[(η^{n} - C_{3} H_{5}) Mn (CO)_{4}]$ follows the E.A.N. rule.

Write the hapticity of the C₃H₅⁻ ligand.

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Answer:

Solution:

To follow the EAN rule:

Complex: $[(η^{n} - C_{3} H_{5}) M n (CO)_{4}]$

Mn is group 7 → Mn contributes 7 e⁻ (oxidation state 0 assumed here since allyl is anionic).

CO is neutral, 4 CO = 8 e⁻.

So far: $7 + 8 = 15 e^{-}$

For the EAN rule (18 e⁻ total), the ligand must donate 3 e⁻.

Allyl C₃H₅⁻ gives:

* $η^{1} \to 1 e^{-}$

* $η^{2} \to 2 e^{-}$

* $η^{3} \to 3 e^{-}$ (best fit)

So hapticity = $η^{3}$

Final answer: C ( $η^{3}$ )

Chemistry - Coordination Chemistry Question with Solution | TestHub

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