18.1 _ Lewis Acids and Bases

Which of the following could not act as a ligand in a complex ion with a transition metal? a) Cl- b) NCl3 c) PCl3 d) CH4

d) CH4 because it does not possess a lone pair

electrophile

an electron-deficient species that accepts a lone pair from another reactant to form a new covalent bond

Lewis acid-base reactions result in

the formation of a covalent bond, which will always be a coordinate bond because both the electrons come from the base

Lewis acid and lewis base define

Acid: lone pair acceptor Base: lone pair donor

How can all Bronsted-Lowry acid-base reactions be classified under Lewis, but Lewis cannot be classified under Bronsted Lowry?

All Bronsted-Lowry involves a transfer of lone pairs of electrons. However, reactions according to Lewis where no transfer of H+ occurs does not fall under Bronsted-Lowry

For each of the following, identify the lewis acid and the Lewis base: a) 4NH3 + Zn2+ --> [Zn[NH3)4]2+ b) 2Cl- + BeCl2 --> [BeCl4]2- c) Mg2+ + 6H2O --> [Mg(H2O)6]2+

a) acid = Zn2+ base = NH3 b) acid = BeCl2 base = Cl- c) acid = Mg2+ base = H2O

Ligands and Lewis acid-base theory

Ligands donate a lone pair of electrons in a coordinate bond, and therefore act as Lewis bases

Lewis acid-base theory and transition metals

Transition metals form ions with vacant d-orbitals. They are able to act as Lewis acids by accepting lone pairs of electrons when they bond to ligands to form complex ions Ligands therefore act as Lewis bases

nucleophile

an electron rich species that donates a lone pair to form a new covalent bond in a reaction

Which of the following reactions represents and acid-base reaction according to Lewis theory but not according to Bronsted-Lowry theory? a) NH3 + HCl --> NH4Cl b) 2H2O <--> H3O+ + OH- c) Cu2+ + 4NH3 <--> [Cu(NH3)4]2+ d) BaO + H2O <--> Ba2+ + 2OH-

c) Cu2+ + 4NH3 <--> [Cu(NH3)4]2+ as there is no exchange of H+