1. Chapter 9 Lecture 1 Coordination Chemistry Structure
History of Coordination Chemistry
Definitions
Coordination Compound = new chemical compounds formed by the binding of simpler, yet distinct, molecules by non-covalent bonds
Simple Covalent Bond = bond formed by the sharing of one electron from each member. H3C• •H H3C—H
Coordinate Covalent Bond = bond formed by the donation of both electrons from one member. H3N: Ni Ni2+—NH3
Other non-covalent interactions
Hydrogen Bonding
p-p bonds

2. Early theory of coordination compound structure
Ligand = atom, ion, or molecule that can donate a pair of electrons to a metal ion (A Lewis Base) = H2O, NH3, Cl-
Werner Complexes
Alfred Werner ( ) was the father of modern coordination chemistry
Early theory of coordination compound structure
Blomstrand ( ) and Jorgenson ( )
The “valence” or charge of the metal ion determined how many bonds it could form: Co3+ could form 3 bonds
This idea stressed the similarity to organic chemistry (C could form 4 bonds)
NH3 could form chains, just like chains of CH2
Only Cl- attached to an NH3 could dissociate
Evidence:
-Amount of AgCl precip
-Conductance Value

3. Werner’s Theory
Metals interact with 6 ligands in octahedral geometry to form “complex ions”
Primary or Inner Coordination Sphere = ligands with bonds to Metal
Secondary or Outer Coordination Sphere = more loosely bound anions present only to balance charge
Explains multiple complexes of the same sets of ligands in diff. numbers
[Co(NH3)6]Cl3 [Co(NH3)5Cl]Cl2 [Co(NH3)4Cl2]Cl [Co(NH3)3Cl3]
Different numbers of ions are produced due to outer sphere dissociation
Explains multiple complexes with exact same formula = isomers
Finally convinced Jorgenson by synthesizing both
Optical Activity
only possible for
octahedral structure

5. Further ideas of Werner proved correct as well
His use of “inert” or slow-reacting metal ions (Co3+, Cr3+, Pt2+) let him successfully isolate all of the isomers
Coordination Number = the number of ligands a given metal ion prefers to have bound. Most first row transition elements prefer 6. Pt2+ prefers 4 = square planar geometry.
CoA4B2 only has two isomers. Trigonal Prismatic and Trigonal Antiprimatic should give 3 isomers. Octahedral only has two possible isomers. Thus the structure must be Oh.
PtA2B2 only has two isomers. It must be square planar rather than tetrahedral, which would only have 1 isomer.
Water completes the Inner Sphere coordination in aqueous solutions: NiCl H2O [Ni(H2O)6]Cl2
For his work on Coordination Chemistry, Werner was awarded the Nobel Prize in 1913

7. Nomenclature of Coordination Complexes
Problem with Werner’s Theory: disobeys octet rule. Solution: use d-orbitals so it becomes an 18-electron rule. [Co(NH3)6]3+ has 6 d e e- from NH3
1s + 3p + 5d orbitals x 2 e- each = 18 total electrons possible
Nomenclature of Coordination Complexes
Ligands
Ligands are often organic molecules with IUPAC names
Common names are most often used for the ligands in coordination compounds
Chelate = Greek for Claw = a ligand that can bind a metal ion by more than one point of attachment.
Bidentate = “two teeth” = NH2CH2CH2NH2 = ethylenediamene = en
Tridentate = NH2CH2CH2NHCH2CH2NH2 = diethylenetriamine = trien
Tetradentate = cyclam
Table 9-2 lists common ligands, names, structures, and abbreviations

11. Naming and Writing Formulas of Coordination Compounds
The cation comes first, then the anion(s)
diamminesilver(I) chloride [Ag(NH3)2]Cl
potassium hexacyanoferrate(III) K3[Fe(CN)6]
Inner Sphere Complex Ion is enclosed in brackets
Ligands are named before the metal
Metal is written first in the formula
A space only between cation and anion
No capitalization is needed
tetraamminecopper(II) sulfate [Cu(NH3)4]SO4
hexaamminecobalt(III) chloride [Co(NH3)6]Cl3
Prefixes denote the number of each ligand type. Special prefixes and parentheses are used if the ligand already contains a prefix.
2 di bis hexa hexakis
tri tris 7 hepta heptakis
tetra tetrakis 8 octa octakis
penta pentakis 9 nona nonakis
10 deca decakis

12. dichlorobis(ethylenediamine)cobalt(III) fluoride [Co(en)2Cl2]F
tris(bipyridine)iron(II) chloride [Fe(bipy)3]Cl2
Ligands are named in alphabetical order not counting prefixes.
tetraamminedichlorocobalt(III) [Co(NH3)4Cl2]+
amminebromochloromethylamineplatinum(II) [Pt(NH3)BrCl(CH3NH2)]
Ligand name alterations:
Anionic ligands are given an -o suffix: chloro, fluoro, oxo, sulfato
Neutral ligands keep their name: methylamine, bipyridine
Water becomes aqua
NH3 becomes ammine to keep separate from alkylamines
Two systems for showing charge or oxidation state of metal ion
Stock system: oxidation state in Roman Numerals in parenthesis after the metal ion name. This is the most common method.
Ewing-Basset system: charge of the total complex ion is placed in parenthesis after the name of the metal ion.

13. Both systems add –ate to the metal name if the complex ion has an overall (-) charge
[Pt(NH3)4]2+ = tetraamineplatinum(II) or (2+)
[PtCl4]2- = tetrachloroplatinate(II) or (2-)
[PtCl6]2- = hexachloroplatinate(IV) or (2-)
Isomer designations come before the rest of the name and in italics
cis-diamminedichloroplatinum(II)
trans-diamminedichloroplatinum(II)
8) Bridging ligands have the prefix m
[(NH3)4Co(OH)(NH2)Co(NH3)4]4+ =
m-amido-m-hydroxobis(tetraaminecobalt(III))
Negatively charged complexes of metals originally having Latin names:
Fe = ferrate Ag = argenate Sb = stibate Au = aurate
Pb = plumbate Sn = stannate Au = aurate
Exception: Hg still called mercurate (Latin name: hydrargyrum)