Chapter 26: Transition Metals and Coordination Compounds

Determine the oxidation state and coordination number of the metal ion in [Cu(CN)4]^2−

+2, 4

Determine the oxidation state and coordination number of the metal ion in [Co(NH3)3Cl3]^−1

+2, 6

Determine the oxidation state and coordination number of the metal ion in [Cr(H2O)6]^3+

+3, 6

How many unpaired electrons are there in the complex ion [Co(CN)6]^4- ?

1

Estimate the crystal field splitting energy (in kJ/mol) for a complex ion that is red in solution.

228 kJ/mol

How many unpaired electrons are there in the complex ion [CoF6]^3- ?

4

How many unpaired electrons are there in the complex ion [FeCl6]^3- ?

5

Typical strong field ligands

CN^-1 > NO2^-1 > en > NH3

polydentate

Describes ligands that donate more than one electron pair to the central metal. (Ex: EDTA, donates 6 electron pairs.)

monodentate

Describes ligands that donate only one electron pair to the central metal.

bidentate

Describes ligands that donate two electron pairs to the central metal. (ethylenediamine, oxalate)

Which metal has the highest first ionization energy? a. Ti b. Mn c. Ru d. Au

Gold

Typical Weak-Field Ligands

H20 > OH^-1 > F^-1 > Cl^-1 > Br^-1 > I^-1

stereoisomers

Molecules in which the atoms are bonded in the same order but have a different spatial arrangement.

structural isomers

Molecules with the same molecular formula but different structures.

Write the formula for the following: ammonium diaquatetrabromovanadate(III)

NH4[V(H2O)2Br4]

coordinate covalent bond

The bond formed when a ligand donates electrons to an empty orbital of a metal in a complex ion.

chelating agent

The coordinating ligand of a chelate.

coordination number

The number of molecules or ions directly bound to the metal atom in a complex ion.

secondary valence

The number of molecules or ions directly bound to the metal atom in a complex ion; also called the coordination number.

primary valence

The oxidation state on the central metal atom in a complex ion.

lanthanide contraction

The trend toward leveling off in size of the atoms in the third and fourth transition rows due to the ineffective shielding of the f sublevel electrons.

optical isomers (enantiomers)

Two molecules that are nonsuperimposable mirror images of one another.

chiral

a molecule that is not superimposable on its mirror image

Diamagnetic

all electrons are paired

Strong Field Ligand or Weak Field Ligand: CN ^-1

Strong Field

Strong Field Ligand or Weak Field Ligand: NH3

Strong Field

Strong Field Ligand or Weak Field Ligand: NO2 ^-1

Strong Field

Strong Field Ligand or Weak Field Ligand: en

Strong Field

Name the following: [Co(H2O)4(NH3)(OH)]Cl2

aminetetraaquahydroxycobalt(III) chloride

heme

an iron ion coordinated to a porphyrin

Which complex(es) ion is(are) diamagnetic? a. [Cr(H2O)4Cl2]^+ b. [Fe(H2O)6]^2+ c. [Co(NH3)6]^3+ d. [CoCl6]^3−

c. [Co(NH3)6]^3+

Paramagnetic

has unpaired electrons

Octahedral Splitting

three orbitals on the bottom, two on the top

crystal field theory

A bonding model for coordination compounds that focuses on the interactions between ligands and the central metal ion.

strong-field complexes

A complex ion in which the crystal field splitting is large.

weak-field complexes

A complex ion in which the crystal field splitting is small.

chelate

A complex ion that contains either a bi- or polydentate ligand.

low-spin complex

A complex ion with strong field ligands that have fewer unpaired electrons than the free metal ion.

high-spin complex

A complex ion with weak field ligands that have the same number of unpaired electrons as the free metal ion.

coordination compound

A neutral compound made when a complex ion combines with one or more counterions.

ligand

A neutral molecule or an ion that acts as a Lewis base with the central metal ion in a complex ion.

complex ion

An ion that contains a central metal ion that is bound to one or more ligands.

Write the formula for the following: tetraaquaplatinum(II) hexachloroplatinate(IV)

[Pt(H2O)4][PtCl6]

What is a common use of coordination complexes?

Coloring agents - inks, paints, cosmetics

crystal field theory

Crystal field theory (CFT) is a bonding model for transition metal complexes that helps us to understand their colors and magnetic properties.

geometric isomers

For complex ions, isomers that result when the ligands bonded to the metal have a different spatial arrangement.

coordination isomers

Isomers of complex ions that occur when a coordinated ligand exchanges places with the uncoordinated counter-ion.

linkage isomers

Isomers of complex ions that occur when some ligands coordinate to the metal in different ways.

porphyrin

a flat polydentate ligand with four nitrogen atoms that can coordinate to a central metal atom

Name the following: [K3[Fe(CN)6]

Potassium hexacyanoferrate(III)

Strong Field Ligand or Weak Field Ligand: Br ^-1

Weak Field Ligand

Strong Field Ligand or Weak Field Ligand: Cl ^-1

Weak Field Ligand

Strong Field Ligand or Weak Field Ligand: F ^-1

Weak Field Ligand

Strong Field Ligand or Weak Field Ligand: H20

Weak Field Ligand

Strong Field Ligand or Weak Field Ligand: I ^-1

Weak Field Ligand

Strong Field Ligand or Weak Field Ligand: OH ^-1

Weak Field Ligand

fac-mer isomerism

When three identical ligands occupy one face of an octahedron, the isomer is said to be facial, or fac. In a fac isomer, any two identical ligands are adjacent or cis to each other. If these three ligands and the metal ion are in one plane, the isomer is said to be meridional, or mer.

How many unpaired electrons are there in the complex ion [Co(NH3)5NO2]^2+ ?

Zero

What is the electron configuration of the Cu+ ion?

[Ar]4s0 3d10

Write the formula for the following: tris(ethylenediamine)cobalt(III) trioxalatoferrate(III)

[Co(en)3][Fe(ox)3]

Which complex ion can exhibit geometric isomerism? Assume that M is the metal ion, A and B are ligands, and the geometry is octahedral. a. [MA6]^2+ b. [MA5B]^2+ c. [MA4B2]^2+ d. [MA3B3]^2+

[MA4B2]^2+

Write the formula for the following: pentacarbonylchloromanganese(I)

[Mn(CO)5Cl]

What is the formula of hexaaquamanganese(II) sulfate?

[Mn(H2O)6]SO4

Name the following: [Fe(NH3)5Br]SO4

pentaamminebromoiron(III) sulfate

Name the following: [Mn(CO)(NH3)5]SO4

pentaamminecarbonylmanganese(II) sulfate

What is the name of the compound [CoCl(NH3)5]Cl2?

pentaamminechlorocobalt(III) chloride

Name the following: [Cr(H20)5Cl]Cl2

pentaaquachlorochromium(III) chloride

Name the following: Na[Cr(H2O)2(ox)2]

sodium diaquadioxalatochromate(III)

Na2[PtCl4]

sodium tetrachloroplatinate(II)

According to valence bond theory, what is the hybridization of the central metal ion in an octahedral complex ion?

sp3

Name the following: [Co(en)3][Fe(CN)6]

tris(ethylenediamine)cobalt(III) hexacyanoferrate(III)

Tetrahedral splitting

two on the bottom, three on the top

Use crystal field theory to determine the number of unpaired electrons in the complex ion [Fe(CN)6]^4−.

zero

crystal field splitting energy

Δ = hv Δ =hc/λ h = Planck's constant v = frequency λ = wavelength