The value of magnetic moment will be independent of temperature for(acac = acetylacetonato; OAc = acetate… · ABC26IN1142

Subject: Inorganic Chemistry · Chapter: Coordination Chemistry · Topic: Coordination Chemistry – General · Exam: CSIR NET JUNE 2019 · Marks: 2 · Difficulty: Medium

The value of magnetic moment will be independent of temperature for(acac = acetylacetonato; OAc = acetate; o-phen = o-phenathroline; Pz = pyrazolyl)
(a)$\left[\mathrm{Fe}(\mathrm{acac})_{3}\right]$
(b)$\left[\mathrm{Cu}(\mathrm{OAc})_{4}\left(\mathrm{H}_{2} \mathrm{O}\right)_{2}\right]$
(c)$\left[\mathrm{Fe}(\text { o-phen })_{2}(\mathrm{NCS})_{2}\right]$
(d)$\left[\mathrm{Fe}\left\{\mathrm{HC}(3,5\text{-}\mathrm{Me}_{2}\mathrm{Pz})_{3}\right\}_{2}\right]^{2+}$
Answer
Answer: A ✓ checked by 4AB · confidence high
Explanation
[Fe(acac)₃] is high-spin d⁵ (⁶A₁g): no orbital contribution and no spin crossover, so μ is temperature-independent. Cu(OAc)₂ dimer is antiferromagnetically coupled, Fe(phen)₂(NCS)₂ and the Fe(II) tris-pyrazolylmethane complex show spin crossover.

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