15.6: Discussion Questions

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Discuss periodic trends in the Lewis acidity of metal ions.
Explain what we mean by hard and soft acids and bases, using specific examples.
Explain why hard and soft should not be equated with electrostatic and covalent.
According to HSAB theory Cu and Zn are classiﬁed as intermediate acids while Cd is classiﬁed as soft. The base (CH₂)₄O is considered hard while (CH₂)₄S is soft. Using E and C numbers for Cd[N(Si(CH₃)₃]₂ and ZnTPP calculate the enthalpies for these two acids interacting with (CH₂)₄O and (CH₂)₄S and show that the HSAB model correctly predicts which base interacts more strongly with which acid. Do the same comparison using Cu(HFacac)₂ as the acid and show that HSAB fails to predict which base interacts more strongly. How are these results related to the Cramer-Bopp plot that show one property or one parameter cannot be used to rank Lewis acid or base strength?