Q75 · CSIR-NET Chemistry, December 2014

Paper: CSIR-NET December 2014 · Subject: Inorganic Chemistry · Chapter: Organometallic Compounds · Topic: 18 Electron Rule · Marks: 2 · Difficulty: Medium

Complexes $\mathrm{HM}(\mathrm{CO})_{5}$ and $\left[\left(\eta^{5}\text{-}\mathrm{C}_{5} \mathrm{H}_{5}\right) \mathrm{M}^{\prime}(\mathrm{CO})_{3}\right]_{2}$ obey the 18-electron rule. Identify M and $\mathrm{M}^{\prime}$ and their ${}^{1}\mathrm{H}$ NMR chemical shifts relative to TMS.
(a)$\mathrm{M}=\mathrm{Mn},-7.5 ; \mathrm{M}^{\prime}=\mathrm{Cr}, 4.10$
(b)$\mathrm{M}=\mathrm{Cr},-4.10 ; \mathrm{M}^{\prime}=\mathrm{Mn},-7.5$
(c)$\mathrm{M}=\mathrm{V},-7.5 ; \mathrm{M}^{\prime}=\mathrm{Cr}, 4.10$
(d)$\mathrm{M}=\mathrm{Mn},-10.22 \mathrm{M}^{\prime}=\mathrm{Fe}, 2.80$
Answer
Answer: A ✓ checked by 4AB · confidence high
Explanation
HMn(CO)₅ (δ −7.5) and [CpCr(CO)₃]₂ (δ 4.1) (a).

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