The correct order of vco for the compounds [Mo(CO)₃ (NMe₃)₃], [Mo(CO)₃ (P(OPh)₃)₃], [Mo(CO)₃(PMe)₃], [Mo(CO)₃… · ABC26IN0505

Subject: Inorganic Chemistry · Chapter: Organometallic Compounds · Topic: Cluster Compounds Wade Rules · Exam: GATE 2005-2021 · Marks: 2 · Difficulty: Hard

The correct order of $\mathrm{v}_{\mathrm{co}}$ for the compounds $\left[\mathrm{Mo}(\mathrm{CO})_{3}\left(\mathrm{NMe}_{3}\right)_{3}\right],\left[\mathrm{Mo}(\mathrm{CO})_{3}\left(\mathrm{P}(\mathrm{OPh})_{3}\right)_{3}\right]$, $\left[\mathrm{Mo}(\mathrm{CO})_{3}(\mathrm{PMe})_{3}\right],\left[\mathrm{Mo}(\mathrm{CO})_{3}\left(\mathrm{PCl}_{3}\right)_{3}\right]$ in the IR spectrum is:
(a)$\left[\mathrm{Mo}(\mathrm{CO})_{3}\left(\mathrm{NMe}_{3}\right)_{3}\right]>\left[\mathrm{Mo}(\mathrm{CO})_{3}\left(\mathrm{P}(\mathrm{OPh})_{3}\right)_{3}\right]>\left[\mathrm{Mo}(\mathrm{CO})_{3}\left(\mathrm{PMe}_{3}\right)_{3}\right]>\left[\mathrm{Mo}(\mathrm{CO})_{3}\left(\mathrm{PCl}_{3}\right)_{3}\right]$
(b)$\left[\mathrm{Mo}(\mathrm{CO})_{3}\left(\mathrm{PCl}_{3}\right)_{3}\right]>\left[\mathrm{Mo}(\mathrm{CO})_{3}\left(\mathrm{NMe}_{3}\right)_{3}\right]>\left[\mathrm{Mo}(\mathrm{CO})_{3}\left(\mathrm{P}(\mathrm{OPh})_{3}\right)_{3}\right]>\left[\mathrm{Mo}(\mathrm{CO})_{3}\left(\mathrm{PMe}_{3}\right)_{3}\right]$
(c)$\left[\mathrm{Mo}(\mathrm{CO})_{3}\left(\mathrm{PCl}_{3}\right)_{3}\right]>\left[\mathrm{Mo}(\mathrm{CO})_{3}\left(\mathrm{P}(\mathrm{OPh})_{3}\right)_{3}\right]>\left[\mathrm{Mo}(\mathrm{CO})_{3}\left(\mathrm{PMe}_{3}\right)_{3}\right]>\left[\mathrm{Mo}(\mathrm{CO})_{3}\left(\mathrm{NMe}_{3}\right)_{3}\right]$
(d)$\left[\mathrm{Mo}(\mathrm{CO})_{3}\left(\mathrm{PMe}_{3}\right)_{3}\right]>\left[\mathrm{Mo}(\mathrm{CO})_{3}\left(\mathrm{NMe}_{3}\right)_{3}\right]>\left[\mathrm{Mo}(\mathrm{CO})_{3}\left(\mathrm{PCl}_{3}\right)_{3}\right]>\left[\mathrm{Mo}(\mathrm{CO})_{3}\left(\mathrm{P}(\mathrm{OPh})_{3}\right)_{3}\right]$
Answer
Answer: C ✓ checked by 4AB · confidence high
Explanation
A better π-acceptor co-ligand leaves less electron density for back-donation to CO, raising ν_CO. Acceptor strength PCl₃ > P(OPh)₃ > PMe₃ > NMe₃, so ν_CO follows the same order.

Study loop for Organometallic Compounds

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