In the brown ring complex [Fe(H2O)5NO]^2+, formulated as iron bound to NO+, the nitrogen of nitrate changes from +5 to +3 in NO+. Treating the weak-field aqua complex as high spin, the spin-only magnetic moment of the complex is closest to

JEE Advanced levelSingle correct optionDifficulty 3 of 3qa214

In the brown ring complex $[Fe (H X_{2} O) X_{5} NO] X^{2 +}$ , formulated as iron bound to $NO X^{+}$ , the nitrogen of nitrate changes from $+ 5$ to $+ 3$ in $NO X^{+}$ . Treating the weak-field aqua complex as high spin, the spin-only magnetic moment of the complex is closest to

With

NO X^{+}

, iron is

+ 1

(

x + 1 = + 2

), so it is

d^{7}

with configuration

t_{2 g}^{5} e_{g}^{2}

in the high-spin state. That has 3 unpaired electrons.

μ = n (n + 2) = 15 = 3.87

BM.