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GATE 2025 CY – Question 21

Inorganic Chemistry · Organometallics: 18-Electron rule; metal-alkyl, metal-carbonyl, metal-olefin and metal-carbene complexes and metallocenes. Fluxionality in organometallic complexes. Types of organometallic reactions. Homogeneous catalysis – Hydrogenation, hydroformylation, methanol to acetic acid process, olefin metathesis and Wacker oxidation. Heterogeneous catalysis – Fischer-Tropsch reaction, Ziegler-Natta polymerization. · 1 mark · Multiple select

The Vaska’s complex trans-IrCl(CO)(PPh3)2 shows a band at 1967 cm-1 for the νCO stretching vibration in its infrared spectrum. The complex(es) that will show an increase in the νCO stretching vibration from 1967 cm-1 is/are

Four substituted or oxidized analogues of Vaska’s complex.
  1. Option A in the figure
  2. Option B in the figure
  3. Option C in the figure
  4. Option D in the figure

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Show answer and explanation

Correct answer: (C) Option C in the figure; (D) Option D in the figure

Explanation

Oxidative addition of oxygen in C reduces metal-to-CO back donation, strengthening CO. The cationic acetonitrile complex D is also less electron rich than Vaska’s complex. The stronger donor ligands in A and B lower the CO frequency.