Coordination Compounds - Result Question 36
####38. Which of the following is the correct order of increasing field strength of ligands to form coordination compounds?
[2020]
(a) $SCN^{-}<F^{-}<CN^{-}<C_2 O_4^{2-}$
(b) $F^{-}<SCN^{-}<C_2 O_4^{2-}<CN^{-}$
(c) $CN^{-}<C_2 O_4^{2-}<SCN^{-}<F^{-}$
(d) $SCN^{-}<F^{-}<C_2 O_4^{2-}<CN^{-}$
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Solution:
- (d) According to spectrochemical series, the order of ligand field strength is $I^{-}<Br^{-}<SCN^{\ominus}<Cl^{-}<S^{2-}<F^{-}<OH<C_2 O_4^{2-}$
$<H_2 O<NCS^{\ominus}<$ EDTA $^{4-}<NH_3<$ en $<\stackrel{\ominus}{CN}<CO$
So, correct order is
$SCN^{-}<F^{-}<C_2 O_4^{2-}<CN^{-}$
Strong and weak field ligands affect the electronic configuration of elements of first transition series. Second and third transition series electrons pair up irrespective of nature of ligand provided pairing of electrons is allowed.
