Paper: CSIR-NET June 2018 · Subject: Inorganic Chemistry · Chapter: Organometallic Compounds · Topic: Organometallic Compounds – General · Marks: 2 · Difficulty: Medium
The structures of $\left[\mathrm{Re}_{2} \mathrm{Cl}_{8}\right]^{2-}(\mathrm{A})$ and $\left[\mathrm{Os}_{2} \mathrm{Cl}_{8}\right]^{2-}(\mathrm{B})$ are made up of two $\mathrm{MCl}_{4}$ units. For these structure which statement is correct?
(a)(A) and (B) both have $\mathrm{MCl}_{4}$ units eclipsed.
(b)(A) and (B) both have $\mathrm{MCl}_{4}$ units staggered.
(c)(A) has both $\mathrm{MCl}_{4}$ units staggered and (B) has both $\mathrm{MCl}_{4}$ units eclipsed.
(d)(A) has both $\mathrm{MCl}_{4}$ units eclipsed and (B) has both $\mathrm{MCl}_{4}$ units staggered.
Answer
Answer: D ✓ checked by 4AB · confidence high
Explanation
[Re₂Cl₈]²⁻ (d⁴–d⁴, σ²π⁴δ²) needs the eclipsed geometry for its δ bond; [Os₂Cl₈]²⁻ (d⁵–d⁵, σ²π⁴δ²δ*²) has no net δ bond and relaxes to the staggered form.