Coordination chemistry (Inorganic semester 2)

What is the Hard Soft Acid Base (HSAB) theory?

• When hard acids prefer to associate with hard bases

• Soft acids prefer to associate with soft bases

What are some properties of hard acids (metals) and provide examples

• Small, highly charged metal cations

• Low polarisability

• Good sigma-acids

• High oxidation states

• Examples = H+, Li+, Na+ ,CO3+, Cr3+, Sc3+

What are the properties of hard bases (ligands) and provide examples

• High electronegativity

• Low polarizability

• Poor pi acids (No vacant pi-acceptor orbitals) so often pi-bases

• Not easily oxidised

• Examples = Amines and ammonia, O- donors (H2O,OH-)

• F-

What are the properties of soft acids (metals) and provide examples

• Large, zero or low charge metal atoms or cations

• High polarizability

• Good sigma-bases

• Examples = Ru, Os, Rh, Pd, Hg

What are the properties of soft bases (ligands) and provide examples

• Low electronegativity

• High polarizability

• Good pi-acids of d-electrons

• Easily oxidised

• Examples = Phosphine (P), As, S, Se, Alkyls,alkenes, CO, and Se donors

How can hard-soft characters be thought of?

In terms of molecular or atomic polarisabilities

What is the equation for working out induced dipole moment (mu)?

• Mu = Induced dipole moment

• E = Electric field strength

• Alpha = Polarisability

What are the units for polarisability?

J^-1 C² m²

Do soft donors / acceptors have high polarizability (alpha) values?

Yes e.g = S, Pb^II

Do hard donor / acceptors have high polarizability (alpha) values?

No, have low values e.g = F^- and Co³⁺

How is sulfur have a high polarizability value?

How does fluorine have a low polarizability value?

What’s the difference between thermodynamics and kinetics?

• Kinetics focuses on rate of reaction and factors that influence it like temp, conc and catalysts

• Thermodynamics deals with energy changes that occur during a reaction and the equilibrium state it reaches (diagram below shows reaction profile of thermodynamics)

How is thermodynamics represented as a letter?

K (UPPER CASE)

How is kinetics represented as a letter?

k (lower case)

What are labile complexes?

Complexes that exchanges ligands rapidly

What are inert complexes?

Complexes that exchanges ligands slowly

Do labile complexes have high or low LFSE values?

Low LFSE values

Do inter complexes have high or low LFSE values?

High LFSE values

What is the Ballar twist mechanism?

Shows changes in configuration (e.g CO^III has been resolved into optical isomers)

What is the dissociative mechanism?

Bond breaks to change configuration

What’s the term when metal ions are solvated in solution meaning complex formation occurs?

Ligand substitution reactions

How do you find the final thermodynamics constant K_f of this reaction (use an equation)

What happens if K_f > 1?

Ligand is more strongly bound than H₂O

What happens if K_f < 1?

Ligand is more weakly bounded than H₂O

What’s the general formula to finding thermodynamics constant if more than 1 ligand is replaced?

What is the thermodynamics equation to finding K₁?

What is the thermodynamics equation to finding K₂?

What is the thermodynamics equation to finding K₃?

What are the stepwise formation constants?

K₁ , K₂ and K₃ etc…

What do stepwise formation constant range up to?

~10⁵⁷

What is the [H₂O] value for reactions in water? (reaction of concentration of water in water)?

[H₂O] remains constant ~55.5M assuming 1L of water and density of water being 1 (Use moles = mass/mr and density = mass/volume)

How do you work out overall formation constant? (use general formula)

How do you work out overall formation constant of K₁ and K₂?

What’s the largest to smallest formation constant assuming metal ligand bond energies don’t change very much along the series? (using K₁, K₂, K₃)?

K₁ > K₂ > K₃ etc…

How can positions of equilibria be shifted?

Using concentration effects such as Le Chatelier’s principle and solubility effects