Question

For the following complexes, identify the one that has the largest LFSE (express in terms of e_g, t₂g or e, t₂ and pairing energy E) [Cu(H₂O)₆]²⁺ ; [Cu(pyridine)₆]²⁺ ; [Cu(oxalate)₃]²⁺

Answer 1

The spectrochemical series for ligand in increasing order of delta value is shown as follows:

The higher the delta value stronger is the ligand and stronger the ligand stronger is its ability to force metal electrons to pair up against the Hund's rule. The LFSE is calculated as follows:

It can be seen that the complex [Cu(oxalate)₃ ]²⁺ has the lowest LFSE and since, the pyridine ligand is strongest therefore, the complex [Cu(pyridine)₆ ]²⁺ will have the largest LFSE.