Hard soft acid base theory summarised Flashcards
What sort of bases do hard acids prefer binding with
Hard bases
What sort of bases do soft acids prefer binding with
Soft bases
What do transition metals act as and what do ligands act as
Transition metals act as Lewis acids and ligands act as Lewis bases
Describe the features of hard acids
Small ionic radius
High positive charge
Low electronegativity
High energy LUMO
Describe the features of a soft acid
Large ionic radius
Low positive charge
Intermediate electronegativity
Low energy LUMO
Describe the features of hard bases
Small radius
High electronegativity
Weak polarizability
High energy HOMO
Describe the features of soft bases
Large radius intermediate electronegativity
High polarizability
Low energy HOMO
Compare hard and soft acids
Large metal ions are soft acids, large electron clouds which experience induced dipoles, small metal ions are hard acids
Compare hard and soft bases
If a lone pair or negative charge is highly localised on a singular small atom it would be a hard base, if the charge is distributed around a larger molecular volume or atom with a larger radius it would be a soft base
What affects the hardness of metals
The greater the charge on the metal ion the harder it is, the smaller the radius the harder it is
What sort of bonds to hard acids and bases form
Ionic bonds
What sort of bonds do soft acids and bases form
Covalent bonds
Describe where the hard acids are on the periodic table and give examples
Early transition metals with valence electrons in the 3d sub shell are hard acids
Describe where the hard bases are on the periodic table and give examples
Hard bases are small anions/ neutral molecules with hone pairs. This of N,O,F
For example F-, O2-, OH-, RO-, NH3, NR3
Describe where the soft acids are on the periodic table
Late 4-5d transition metals tend to be soft especially those with only a 1-2+ charge
