Complex Ions, Coordination Compounds, & Isomers

Formation Constant

Kf

• Complex ions are very stable species

• It is nearly guaranteed that these formation reactions will run to completion

  • LR is completely consumed

• Complex ions have a very large Kf value

Dissociation Constant

Kd

• The inverse of Kf

• Kd = 1/Kf

Solubility and Complex Ions

Combine the dissolution and formation reactions to determine how much of the solid dissolves

• Keq = Kf x Ksp

Solubility and pH

Introducing acid to a precipitate

• Acid shifts the equilibrium of the dissolution to the right

• Solubility increases

Transition Elements

• d block elements with partially filled d orbitals

• Groups 3 -11 in the periodic table

• Group 12 are technically not transition elements even though they’re in the d block

Transitions Elements: Metals

• Lose electrons to form cations

• Variable degrees of oxidation

• Some ions are part of polyatomic anions

  • There are a lot of e- situation in the s and d orbitals (energy difference is variable)

Coordination Chemistry

Metal participate in formation of coordinative covalent bonds

• The central atom/ion is the Lewis acid

• Ligands bind via coordinative covalent bonds

• Counter ions

Coordination Number

Number of donor atoms (bonds) attached to the central atom/ion

• 2, 4, and 6 are most common

• 2: linear

• 4: square planar

• 4: tetrahedral

• 6: octahedral

Monodentate Ligand

Binds to the metal via a single coordinative covalent bond

• Only have one bond that they can contribute

Polydentate Ligand

A single ligand can bind to the metal via several covalent bonds

• Bidentate

• tridentate

• Tetradentate

• Pentadentate

• Hexadentate

Naming: Ionic and Complex Ions

• Start with the cation then the anion

• First name the ligand (alphabetical order) and then the metal

Naming: Negative Ligands

Add o to the name of the anion

• Example: F- = fluoro, Cl- = chloro, CN- = cyano

Naming: Neutral Ligands

Just the name of the molecule

• Exceptions:

  • Aqua (H2O)

  • Amine (NH3)

  • Carbonyl (CO)

  • Nitrosyl (NO)

Number of Ligands

Use Greek prefixes

• Di, tri, tetra, penta, hexa, etc.

• Bis, tris, and tetrakis are used for polydentate ligands

Naming Coordination Compounds: Example

• Na[Al(H₂O)₂(OH)₄]: sodiumdiaquatetrahydroxaluminate

  • Don’t need to specify charges b/c Al is not a transition metal

• [Cu(H₂NCH₂CH₂NH₂)₂(H₂O)₂](NO₃)₂: diaquabise(ethylendiamine)copper(II)nitrate

  • Polydentate ligand

Structural Isomers

Molecules that have the same number and type of atoms but are attached in a different oder

Stereoisomers

Molecules that have the same number, type, and order but differ in their 3D orientation

Stereoisomers: Geometric Isomer

Molecules that have the same number, type, and attachment order but the atoms or groups of atoms point in a different spatial direction

Stereoisomers: Optical Isomers (Enantiomers)

Molecules that are exact mirror images of each other but cannot be lined up so that all parts match (NOT superimposable)

• Superimposable: no matter how the molecule is rotated, the two will never match

• If plane of symmetry is present - enantiomer doesn’t exist

Linkage Isomers

Structural isomers that have ligands attached to the central cation through different ends of the ligand structure (different bonds)

• Physical properties are not the same

Cis Isomerism

Two ligands are adjacent to each other in the structure

Trans Isomerism

Two ligands are opposite of each other in the structure