The CORRECT order of pKa for the compounds I to IV in water at 298 K is IHCo(CO)₄ IIHCo(CO)₃(PPh₃)… · ABC26IN0769
Subject: Inorganic Chemistry · Chapter: Organometallic Compounds · Topic: Organometallics – General · Exam: JAM 2005-2022 · Marks: 2 · Difficulty: Hard
The CORRECT order of $\mathrm{pK}_{\mathrm{a}}$ for the compounds I to IV in water at 298 K is \[ \underset{\text{I}}{\mathrm{HCo(CO)_4}} \quad \underset{\text{II}}{\mathrm{HCo(CO)_3(PPh_3)}} \quad \underset{\text{III}}{\mathrm{HCo(CO)_3(P(OPh)_3)}} \quad \underset{\text{IV}}{\mathrm{HCo(CO)_2(PPh_3)_2}} \]
(a)I $>$ III $>$ II $>$ IV
(b)IV $>$ II $>$ III $>$ I
(c)IV $>$ III $>$ II $>$ I
(d)I $>$ II $>$ III $>$ IV
Answer
Answer: B ✓ checked by 4AB · confidence high
The source book printed D; on checking, B is correct — see the explanation.
Book printed (d).
Explanation
Better donor ligands make the hydride less acidic: pKa HCo(CO)₂(PPh₃)₂ (IV) > HCo(CO)₃PPh₃ (II) > HCo(CO)₃P(OPh)₃ (III) > HCo(CO)₄ (I) (b).
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