What is spectrochemical series? Explain the difference between a weak field ligand and a strong field ligand.
The strong ligands have higher splitting power of d orbitals of the central metal ion, whereas weak ligand has relatively lower splitting power of d orbitals of the central metal ion. The energy difference between t2g and eg sets of d orbitals is CFSE. The strength of the ligands depend on the magnitude of Δ . Strong ligands have larger value of CFSE and in case of weak ligands the CFSE values are smaller. The common ligands can be arranged in a series in the order of their decreasing field strength, as follows.
I_<Br -< SCN-< Cl-< F-< OH-< C2O42-< H2O< NCS-< py< NH3< en< bipy< o-phen< NO2-< CN-< CO.
This series depends on the power of splitting the d orbitals and is called spectrochemical series, The order of field strength of the common ligands neither depends on the geometry of the complex the nature of central metal ion.
Using IUPAC norms write the formulas for the following:
(i) Tetrahydroxidozincate (II)
(ii) Potassium tetrachloridopalladate (II)
(iii) Diamminedichloridoplatinum (II)
(iv) Potassium tetracyanidonickelate (II)
(v) Pentaamminenitrito-O-cobalt (III)
(vi) Hexaamminecobalt (III) sulphate
(vii) Potassium tri (oxalato) chromate (III)
(viii) Hexaammineplatinum (IV)
(ix) Tetrabromidocuprate (II)
(x) Pentaamminenitrito-N-cobalt (III)
Write down the IUPAC name for each of the following complexes and indicate the oxidation state, electronic configuration and coordination number. Also give stereochemistry and magnetic moment of the complex:
(i) K[Cr(H2O)2(C2O4)2].3H2O (iii) [CrCl3(py)3] (v) K4[Mn(CN)6]
(ii) [Co(NH3)5Cl-]Cl2 (iv) Cs[FeCl4]