Achieve HW Week 9: problem 3

[Minh Nguyen 3H]

For number 3, the molecular shapes that are common for complexes with a coordination number of 4 is apparently tetrahedral and square planar. I'm confused as to why the seesaw shape is not also common. It includes four atoms that are bound to a central atom, which matches the coordination number of 4. Could someone explain why exactly a seesaw structure isn't common?

[indigoaustin 3H]

This is not common because the see-saw shape includes a lone pair, which will not occur with coordination compounds. This is because they involve coordinate covalent bonds, which imply ligands donating lone pairs. Therefore, the central metal atom in coordinate complexes will not have lone pairs, which is why this shape (and others with lone pairs) is not common.

[Rhea Jain 2I]

I was wondering the same thing too. It's because see-saw has a lone pair on its structure, and coordination compounds don't have lone pairs on ligands.