Question

On the basis of VB theory explain the nature of bonding in \[\ce{[Co(C2O4)3]^3-}\].

Answer 1

In the complex entity \[\ce{[Co(C2O4)3]^3-}\] the Co is in +3 oxidation state. The outer electronic configuration of Co³⁺ is 3d⁶. The oxalato ligand is fairly strong field ligand. So it faces the 3d electrons in Co³⁺ to pair up and make two of the 3d orbitals available for bonding. As a result, Co³⁺ shows d²sp² hybridisation. Electronic configuration of Co atom Electronic configuration of Co³⁺ ion Hybridisation and formation of \[\ce{[Co(C2O4)3]^3-}\]

1. There is no unpaired electron in \[\ce{[Co(C2O4)3]^3-}\] Thus \[\ce{[Co(C2O4)3]^3-}\]

2. During the formtion of \[\ce{[Co(C2O4)3]^3-}\], two of the 3d-orbitals are used in bonding. Therefore it is an inner orbital (low spin) complex.

3. The \[\ce{[Co(C2O4)3]^3-}\] has the octahedral geometry.