Nomenclature

1
Nomenclature

• cation anion
• Where the complex ion is named accordingly
• ( prefix ligand )repeat metal (charge)
• Example
• Co(H2O)5ClCl
• pentaaquachlorocobalt(II) chloride

2
Bidentate Ligands

• Name as you would monodentate ligands
• Except, different prefixes
• (none)
• bis
• tris
• tetrakis
• Examples
• Co(en)(H2O)4Cl2
• Co(en)2(H2O)2Cl2

3
19.4 Isomerism
Isomers Same formula, different structures (and
properties)
Structural Isomers Same atoms, different bonds
Stereoisomers Same bonds, different arrangements
Coordination Isomers
Linkage Isomers
Geometric Isomers
Optical Isomers
4
Isomers
Structural Isomers Same atoms, different bonds
Coordination Isomers Swap ligand and counter ion
Linkage Isomers Same ligand, different bond to
metal
5
Coordination Isomers
Same atoms, but counter ion and ligand switched
6
Linkage Isomers
thiocyanato
isothiocyanato
Same atoms in ligand, but bound to metal through
a different atom. Often named differently.
7
Isomers
Stereoisomers Same bonds, different arrangements
Optical Isomers Different mirror
images (enantiomers)
Geometric Isomers Different positions around
metal (cis and trans)
8
Geometric Isomers

• cis (next to)
• Trans (across from)

Fig 19.11 pg 952
9
Geometric Isomers

• trans

cis
10
Optical Isomers

• These molecules also called chiral
• Chiral molecules have important properties
• Rotate plane polarized light
• Have a different 3-D shape
• Many biological process only work with one
  specific optical isomer
• Chiral Molecules have a non-superimposable mirror
  image

11
Optical Isomers

• Rotating plane polarized light fig 19.14 pg
  954

12
Determining Optical Isomers

• Nonsuperimposable mirror images
• Example Your L and R hands are optical isomers
• The mirror image of R hand can superimpose on L
  hand, but not on R hand

13
Determining Optical Isomers

• Reflect molecule

Not optical isomers!

• If the reflection can not be rotated to
  superimpose on original, these are optical
  isomers.

14
Determining Optical Isomers

• Example

Rotate this 90
Optical isomers!
15
Stereoisomers
16
Wordage

• One structure is chiral
• The cis vs. trans molecules are geometric isomers
  of each other
• Two different forms of the cis version are
  enantiomers of each other

17
Summary Question

• Which could display coordination, linkage,
  geometrical, and optical isomerism?
•     a)  Cr(en)(NH3)4Cl2    b) 
  Cr(en)2(H2O)2Cl2    c)  Cr(NH3)5(SCN)Cl   
  d)  Cr(NH3)4B2Cl2

Coordination They all could Linkage
c Geometrical b and d Optical the cis
isomer of b