Topic 15: Transition Metals

D-block elements that form one or more stable ions with incompletely filled d-orbitals

• hard solids • high melting and boiling temperatures • can act as catalysts • form coloured ions and compounds • form ions with different oxidation numbers • form ions with incompletely filled d-orbitals

Attract electron-rich species more strongly including water molecules present in aq solutions

• bonds are shown with arrow heads indicating dative bonds • whole structure drawn inside square brackets and the original charge of the ion is shown outside the brackets

The total number of dative bonds around the metal ion

A species that uses a lone pair of electrons to form a dative bind with a metal ion

A species containing a metal ion joined to ligands

A complex with an overall positive or negative charge

In order: - number of ligands eg. hexa - name of ligand eg. aqua - name of metal ion eg. iron - oxidation number of the metal ion eg. (II)

Water ligand causes 3d orbital to split into 2 energy levels Electrons in the lower energy level absorb energy from the visible spectrum and are executed to a higher energy level (**) light is transmitted as its complementary colour is absorbed

xenon tetrafluoride XeF4 cis-platin

Cis = identical ligands are next to eachother, Trans = opposite Cis-platin consists of a platinum (II) ion, two ammonia ligands and two chloride ion ligands

• all cells including cancer cells contain DNA • during cell division the 2 strands of DNA must separate from eachother to form more DNA • the structure of cis-platin enables it to form a bond between the 2 strands of DNA, preventing them from separating & so prevents the cancer cells from dividing

Monodentate ligands are ones that form one dative bond with a metal ion Bidentate ligands form 2 dative binds with a metal ion Multidentate ligands form several dative bonds with a metal ion

NH2CH2CH2NH2 (1,2 diaminoethane) sometimes abbreviated to en

EDTA (6 dative bonds)

If the total number of species (ligands) increases, the system becomes more disordered As a result there is an increase in △S(system) Formation of products is favoured due to their increased stability compared to reactants

When haemoglobin collects oxygen, oxygen uses one of its lone pairs of electrons to form a dative bond with one of the Fe2+ ions

• Carbon monoxide has a lone pair of electrons on its carbon atom that enables it to act as a ligand • The strength of the dative bond between oxygen and haemoglobin < strength of dative bond between carbon monoxide and haemoglobin • Therefore any carbon monoxide breathed in is likely to replace the oxygen in a ligand substitution reaction • The oxygen carrying capacity of the blood is reduced as the dative bond is so strong that it does not break easily

• redox : change in oxidation number of metal cation • acid-base reaction : one or more of the ligands loses/gains hydrogen • ligand exchange : substitution of one or more of the ligands around the transition metal ion • coordination number change : number of ligands changes

[Cu(H2O)6]2+. +. 4Cl- ——> [Cu(Cl)4]2- +. 6H2O Acid is added slowly and continuously - colour gradually changes from blue to green to yellow

With OH- : [Cr(H2O)6]3+. +. 3OH- ——>. [Cr(H2O)3(OH)3]. +. 3H2O violet solution - green ppt With excess OH- : [Cr(H2O)3(OH)3]. + OH- ——>. [Cr(H2O)2(OH)4]- +. H2O green ppt - green solution

With OH- : [Fe(H2O)6]2+. +. 2OH- ——> [Fe(H2O)4(OH)2] +. 2H2O pale green solution - green ppt With excess OH- : no further change

With OH- : [Fe(H2O)6]3+. +. 3OH- ——> [Fe(H2O)3(OH)3] +. 3H2O yellow-brown solution - brown ppt With excess OH- : no further change