Which forms the stronger bond with a metal, #"Cl"^(-)# or #"NH"_3#?

1 Answer
Truong-Son N.
Nov 2, 2017

The stronger bond is formed by the better #sigma# donor, the #"NH"_3# ligand. Neither is a #pi# acceptor, which would have also strengthened the bond.

#"CO"# is a #pi# acceptor and a #sigma# donor at the same time. Is a #"M"-"CO"# bond stronger or weaker than an #"M"-"NH"_3# bond?

Between #"Cl"^(-)# and #"NH"_3#, the former is a good #pi# donor and a poor #sigma# donor, but the latter is a good #sigma# donor. Since #sigma# bonds are more direct, they contribute better to a strong bond due to more effective sharing of electron density.

In fact, a #sigma# bond is in general stronger than a comparable #pi# bond.

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