Q48 · CSIR-NET Chemistry, June 2012

Paper: CSIR-NET June 2012 · Subject: Inorganic Chemistry · Chapter: Organometallic Compounds · Topic: Organometallic Compounds – General · Marks: 2 · Difficulty: Medium

For the reaction, trans- $\left[\mathrm{IrCl}(\mathrm{CO})\left(\mathrm{PPh}_{3}\right)_{2}\right]+\mathrm{Cl}_{2} \rightarrow$ trans $-\left[\mathrm{IrCl}_{3}(\mathrm{CO})\left(\mathrm{PPh}_{3}\right)_{2}\right]$ the correct observation
(a)$\bar{\nu}_{\mathrm{CO}}\text{(product)} > \bar{\nu}_{\mathrm{CO}}\text{(reactant)}$
(b)$\bar{\nu}_{\mathrm{CO}}\text{(product)} < \bar{\nu}_{\mathrm{CO}}\text{(reactant)}$
(c)$\bar{\nu}_{\mathrm{CO}}\text{(product)} = \bar{\nu}_{\mathrm{CO}}\text{(reactant)}$
(d)$\bar{\nu}_{\mathrm{CO}}\text{(product)} = \bar{\nu}_{\mathrm{CO}}\text{(free CO)}$
Answer
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Explanation
Oxidative addition of Cl₂ converts Ir(I) to Ir(III), which back-donates less to CO, so ν(CO) rises (≈1965 → 2070 cm⁻¹).

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