Question

Match each Lewis base with the metal ions with which it is most likely to form a stable complex:

Lewis bases: NH3, F−, RS−, OH−, and Cl−
Metals: Sc3+, Cu+, W6+, Mg2+, V3+, Fe3+, Zr4+, Co2+, Ti4+, Au+, Al3+, and Mn7+

Please explain why for each case.

Answer 1

The metal ions act as lewis acid and ligands act as lewis base. The rule is hard acid reacts with hard base and soft acid with soft base.

List of hard acids : Sc3+, W6+, V3+, Mg2+, Zr4+, Fe3+, Ti4+, Al3+, and Mn7+

Soft acid : Cu+, Au+

Borderline : Co2+

Soft base : RS-

Hard base : OH-, F-, Cl-, NH3

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Sc3+   -----> OH-, F-, Cl-, NH3

W6+   -------------> OH-, F-, Cl-, NH3

V3+ ----------------->OH-, F-, Cl-, NH3

Mg2+ -----------> OH-, F-, Cl-, NH3

Zr4+   ---------------> OH-, F-, Cl-, NH3

Fe3+ -----------> OH-, F-, Cl-, NH3

Ti4+ -------------> OH-, F-, Cl-, NH3

Al3+ ----------> OH-, F-, Cl-, NH3

Mn7+ -----------> OH-, F-, Cl- (very high charge on metal hence anions are preferred)

Cu+ -----------> RS-

Au + ------------> RS-

Co2+ --------> OH-, F-, Cl-, RS-