Q.47 Using valence bond theory, explain the following in relation to the complexes given below

${\left[Mn\left(C{N}_{6}\right]}^{3-},{\left[Co{\left(N{H}_{3}\right)}_{6}\right]}^{3+},{\left[Cr{\left({H}_{2}0\right)}_{6}\right]}^{3+},{\left[FeC{l}_{6}\right]}^{4-}$

(a) Type of hybridisation

(b) lnner or outer robital comples

(c) Magnetic behaviour

(d) Spin only magnetic moment value.

${\left[Mn{\left(CN\right)}_{6}\right]}^{3-}$

(i) ${d}^{2}s{p}^{3}$ hybridisation

(ii) lnner orbital complex because (n-1)d-orbitals are used.

(iii) Paramagnetic, as two unpaired electons are present.

(iv) Spin only magnetic moment ($\mu$)=

(b) ${\left[Co{\left(N{H}_{3}\right)}_{6}\right]}^{3+}\phantom{\rule{0ex}{0ex}}C{o}^{3+}=3{d}^{6}4{s}^{0}$

(NH${}^{3}$ pair up the unpaired 3d electons)

(i) ${d}^{2}s{p}^{3}$ hybridisation

(ii) lnner orbital complex because of the invovement of *n-1) d-orbital in bonding.

(iii) Diamagnetic, as no unpaired electron is preset.

(iv)

(c) ${\left[Cr\left({H}_{2}{O}_{6}\right]}^{3+}\phantom{\rule{0ex}{0ex}}$

(i) ${d}^{2}s{p}^{3}$ hybridisation

(ii) lnner orbital complex (as(n-1) d-orbital take part)

(iii) Paramagnetic (as three unpaired electrons are present

(iv)

(d) ${\left[Fe{\left(Cl\right)}_{6}\right]}^{4-}\phantom{\rule{0ex}{0ex}}F{e}^{2+}=3{d}^{6}$

(i) $s{p}^{3}{d}^{2}$ hybridisation

(ii) Outer orbital complex because nd-orbitals are involved in hybridisation.

(iii) Paramagnetic (because of the presence of four unpaired electrons).

(iv) $\mu =\sqrt{n\left(\left(n+2\right)}=\sqrt{4\left(4+2\right)}=\sqrt{24}=4.9BM$