I have been reading about introductory Molecular Orbital Theory lately. Till now, I have used Valence Bond Theory to evaluate bonding. I have a few questions about it:-
In VBT, we used the idea that bonds form when orbitals overlap. In Oxygen molecule, two bonds forms in VBT as the other orbitals were far enough to not overlap . But in MOT we say that all the orbitals overlap to form new MOs. Aren't the two statements contradictory?
In Coordination Compounds, when we study about non-classical $\pi$-acceptor ligands,we say that Bond Order of the ligand decreases when it receives electron pair from transition metal in its Anti-Bonding orbital. However, if I try to use VBT for the same, I feel that Bond Order should increase or at least remain the same as any kind of overlapping leads to stability in VBT. Where am I wrong?
Please try to explain the matter without using complex mathematics.