The correct match of spin-only magnetic moment for the complexes cis-$\left[\mathrm{Fe}(\mathrm{phen})_{2}(\mathrm{NCS}\text{-}\mathrm{N})_{2}\right]$ (A) and $\left[\mathrm{Fe}(\mathrm{phen})_{3}\right]\mathrm{Cl}_{2}$ (B) at 300 K is (phen $=1,10$-phenantholine)
(a)4.89 BM for both A and B
(b)0 BM for both A and B
(c)4.89 BM for A and 0 BM for B
(d)0 BM for A and 4:59 BM for B
Answer
Answer: C ✓ checked by 4AB · confidence high
Explanation
cis-[Fe(phen)₂(NCS)₂] is a spin-crossover complex that is high spin at 300 K: 4 unpaired electrons, 4.89 BM. [Fe(phen)₃]²⁺ is low-spin d⁶ with 0 BM (c).