CBSE Class 12 · 2003 · Delhi · Coordination CompoundsShort Answer

Using the valence bond approach, deduce the shape and magnetic character of [Cr(CO)

_{6}

]. [Atomic number of Cr = 24]

Answer: Octahedral, d²sp³; diamagnetic (Cr(0) 3d⁶ fully paired by strong-field CO).

Solution

In Cr(CO)

_{6}

chromium is in the 0 oxidation state; under the very strong-field CO the configuration rearranges to 3d

^{6}

^{0}

and the six d electrons pair into three orbitals (t

_{2 g}^{6}

).
Two empty 3d + 4s + three 4p → d

^{2}

^{3}

.
Shape: octahedral.
Magnetic character: no unpaired electron → diamagnetic.

CBSE Class 12 Board · 2003 · Delhi · Subjective