question_answer

Which of the following complex compounds will exhibit highest paramagnetic behaviour? [AIPMT (M) 2011]

\[(At.\,no.:Ti=22,Cr=24,Co=27,Zn=30)\]

A) \[{{[Ti{{(N{{H}_{3}})}_{6}}]}^{3+}}\]

B) \[{{[Cr{{(N{{H}_{3}})}_{6}}]}^{3+}}\]

C) \[{{[Co{{(N{{H}_{3}})}_{6}}]}^{3+}}\]

D) \[{{[Zn{{(N{{H}_{3}})}_{6}}]}^{2+}}\]

Correct Answer: C

Solution :

[c] [a] Electronic configuration of \[\text{T}{{\text{i}}^{\text{3+}}}\] in

\[{{[Ti{{(N{{H}_{3}})}_{6}}]}^{3+}}\]

[b] Electronic configuration of \[\text{C}{{\text{r}}^{\text{3+}}}\]in\[{{\text{ }\!\![\!\!\text{ Cr(N}{{\text{H}}_{\text{3}}}{{\text{)}}_{\text{6}}}\text{ }\!\!]\!\!\text{ }}^{\text{3+}}}\]

[c] Electronic configuration of \[\text{C}{{\text{O}}^{\text{3+}}}\]in\[{{\text{ }\!\![\!\!\text{ Co(N}{{\text{H}}_{\text{3}}}{{\text{)}}_{\text{6}}}\text{ }\!\!]\!\!\text{ }}^{\text{3+}}}\text{:}\]

In the presence of strong field ligand \[N{{H}_{3}},\]pairing of electrons takes place and thus, octahedral    complex,\[{{\text{ }\!\![\!\!\text{ Co(N}{{\text{H}}_{\text{3}}}{{\text{)}}_{\text{6}}}\text{ }\!\!]\!\!\text{ }}^{\text{3+}}}\]   is diamagnetic. \[{{\text{ }\!\![\!\!\text{ Co(N}{{\text{H}}_{\text{3}}}{{\text{)}}_{\text{6}}}\text{ }\!\!]\!\!\text{ }}^{\text{3+}}}\]

\[\left[ \begin{align}   & \text{inner}\,\text{orbital}\,\text{or} \\  & \text{low}\,\text{spin}\,\text{complex} \\ \end{align} \right]\text{(6N}{{\text{H}}_{\text{3}}}\,\text{molecules)}\]

[d] Electronic configuration of\[Z{{n}^{2+}}\] in

\[{{[Zn{{(N{{H}_{3}})}_{6}}]}^{2+}}:\]

\[\therefore \]\[{{[Zn{{(N{{H}_{3}})}_{6}}]}^{2+}}\]is an outer orbital complex and is diamagnetic.