Coordination Compounds

Dative Bond (Coordinate Bond)

One of the atoms supplies both the shared electrons to the covalent bond.

Ligands

A molecule that donates a lone pair to a metal

coordination compound

consists of a transition metal with attached ligands and counterions

Which are the counter ions? [Fe(CO)4Cl2]Br

The ions outside the square brackets

Br- in this example

How do you determine charge on the TM in a complex?

Charge on Ligand + Charge on Metal = Charge on complex

Charge on ligands (lewis structure or tables)

Charge on complex based on the counterions

Solve for Charge on metal

oxidation state

The charge of the TM ion (e.g., +1, -2, etc.)

electron configuration of TM ions

the 3d fills before 4s (or 4d before 5s)

d electrons on a metal in a complex

the total number of d electrons given the oxidation state of the metal

Total electrons on TM in a complex

d electrons + 2 electrons per ligand binding site

Denticity

The denticity of a ligand refers to the number of donor atoms it has, and therefore the number of bonds it can make to the transition metal.

denticity of ethylene diamine (en)

NH2CH2CH2NH2

bidentate

denticity of Ph3P

monodentate

denticity of acetoacetate (acac)

bidentate

hapticity

# of atoms of a ligand attached to a metal atom

hapticity of allyl ligand (CH2CHCH2)-

eta-3

hapticity of benzene

eta-6

Ligand names: NH3

ammine

Ligand names: water

aqua

Ligand names: Br-

bromo

Counterion names: Br-

bromide

Ligand names: CN-

cyano

Ligand names: CO

carbonyl

Ligand names: PPh3

triphenylphosphine