Coordination Compounds 2 Question 69
####71. Identify the complexes which are expected to be coloured. Explain
$(1994,2 M)$ (i) $\left[Ti\left(NO _3\right) _4\right]$ (ii) $\left[Cu\left(NCCH _3\right)\right]^{+} BF _4$ (iii) $\left[Cr\left(NH _3\right) _6\right] Cl _3$ (iv) $K _3\left[VF _6\right]$
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Solution:
- (i) $\left[Ti\left(NO _3\right) _4\right]: Ti^{4+}\left(3 d^{0}\right)$ No $d$-electron, no $d$ - $d$ transition possible, colourless.
(ii) $\left[Cu\left(NCCH _3\right)\right] BF _4: Cu^{+}\left(3 d^{10}\right)$ All $d$-orbitals are completely filled, no $d-d$ transition possible, colourless.
(iii) $\left[Cr\left(NH _3\right) _6\right] Cl _3: Cr^{3+}\left(3 d^{3}\right)$ Complex has allowed $d$ - $d$-transitions from $t _{2 g}$ to $e _g$ level, hence coloured.
(iv) $K _3\left[VF _6\right]: V^{3+}\left(3 d^{2}\right)$ Complex has allowed $d$ - $d$-transitions from $t _{2 g}$ to $e _g$ level, hence coloured.
