Transition Metals

Ionic Bonding

transfer of electrons, stable configuration

Covalent Bonding

sharing valence electrons rather than transfer

Coordinate Bond

one of the atoms supplies both electrons

Transition Metals

act as Lewis acids

• form complexes/ complex ions

Complex

contains a central metal ion bonded to one or more molecules or anions

Coordination Number

number of donor atoms bonded to the central metal atom or ion in the complex

• most common = 4, 6

• determined by ligands

  • larger ligands favour lower coordination numbers

Coordination Compound

compound that contains 1 or more complexes

• ions or molecules might be directly bonded to the metal, or serve as a counter ion for an ionic salt

Complex Charge

sum of charges on the metal and the ligands

Ligand

an ion or molecule that donates a pair of electrons to a metal atom or ion in forming a coordination complex

Monodentate Ligand

ligands with one donor atom have just one point of attachment to the central atom or ion

Polydentate Ligand

has more than one point of attachment to the central species

Chelate

complex formed when a 5 or 6 membered ring is produced by the attachment of a polydentate ligand

• generally much more stable

• chelation therapy using EDTA is sometimes used to treat heavy metal poisoning

Anion

if the complex ion is this, metal ending is -ate

Cation

named before the anion when naming an ionic compound

Valence Bond Theory

bonds are formed by overlap of individual atomic orbitals permitting sharing of electrons

• orbitals on individual atomic orbitals can be mixed to from hybrid orbitals accounting for geometries

Crystal Field Theory

• focus: energies of the d orbitals

• assumes:

  • ligands - negative point charges

  • metal-ligand bonding is entirely ionic

• strong field : large splitting of d orbitals

• weak field : small splitting of d orbitals

Isomerism Types

1. ionisation isomerism

2. coordination isomerism

3. linkage isomerism

Cisplatin

very effective but highly toxic antitumour drug

• particularly used in ovarian, testicular and small cell lung cancers

• square planar complex

• analogues have been prepared due to its toxicity

Cisplatin Analogues

common requirements:

• electroneutrality to facilitate transport through cell membranes

• presence of at least 2 leaving groups

• presence of inert carrier ligands, usually non tertiary amine groups which increase adduct stabilisation through hydrogen bonding with nearby bases