2.5 Transition Metals

A metal that can form one or more stable ions with an incomplete d sub-shell

• Complex formation • Formation of coloured compounds • Act as catalysts • Variable oxidation states

A central metal ion surrounded by ligands

A molecule or ion that forms a coordinate bond with a transition metal by donating a pair of electrons

Molecules or ions that donate one electron pair to the central metal ion to form one coordinate bond

Molecules or ions that have two atoms which each donate an electron pair to the central metal ion to form two coordinate bonds

Molecules or ions that have more than two atoms that each donate an electron pair to the central metal ion to form more than two coordinate bonds

The number of coordinate bonds to the central metal atom / ion

Square planar

Oxygen and water. Controlled by equilibrium

• Water ligands on haemoglobin are substituted for CO ligands • Co to Fe bond is very strong • Prevents oxygen from bonding to haemoglobin

• Increase in entropy when a monodentate ligand is replaced by a bidentate / multidentate ligand • Reaction in always feasible and new complex is more stable

Interaction between ligands and electrons causes some orbitals to have more energy than others

• Ions absorb certain frequencies of visible light • Causes d-electrons to be excited • Remaining colours of visible light are transmitted

E = hf f = c / λ E = hc / λ

• Coordination number • Ligand • Oxidation state

Amount of light absorbed by the solution (used to find concentration)

• Plot calibration curve of conc. against abs. for know concentrations • Record abs. for unknown solution and read off conc.

Selects the complementary colour (this is the colour that is absorbed)

Non-destructive technique

Two of the same group next to each other

Tow of the same group opposite each other

+3 Sc³⁺

+2 Ti²⁺ +3 Ti³⁺ +4 TiO₂