Download Chem 106 Thurs 4-21-2011 Ch. 22: Transition Metals 1. Review

Chem 106
Thurs 4-21-2011
Ch. 22: Transition Metals
1. Review periodic table
2. Sources of the elements
3. Coordination compounds
Definitions and examples
Ni2+ complexes: H2O, NH3, ethylenediamine
Bi-dentate ligands
Naming coordination compounds
Complex geometry: linear, square planar, tetrahedral, octahedral
Geometric isomers (cis/trans)
Chiral complexes: mirror image isomers
Transition Metal Chemistry
Transition Metal Chemistry
Gems & Minerals
Citrine and amethyst are quartz (SiO2) with a trace of
cationic iron that gives rise to the color.
Rhodochrosite, MnCO3 (Mn2+ and CO32-)
(manganese (II) carbonate)
Reactions: Transition Metals
Fe + Cl2
Fe + O2
Fe + HCl
Periodic Trends: Atom Radius
Periodic Trends: Oxidation Numbers
Most common
Zn
2B
Electron Configurations and the Periodic Table
Metallurgy: Element Sources
This is explained by the “Hard-Soft- Acid-Base” (HSAB) Theory.
Smaller cations with higher positive charge tend form more stable compounds
with small anions having a high negative charge density. These compounds are
based more on ionic attractive forces.
Larger cations with smaller positive charge tend to form more stable
compounds with large anions with valence electrons in larger, more diffuse
orbitals. These compounds are based more on covalent bonding interactions.
Why the big block
of O2- ores among
the early transition
metals, and the S2ores in the late
transition metals??
Transition metals: Coordination chemistry
• Coordination compound:
– combination of two or
more atoms, ions, or
molecules where a bond
is formed by sharing a
pair of electrons
originally associated with
only one of the
compounds.
CH2
Pt
CH2
-
Cl
Cl
Cl
More examples
Pt(NH3)2Cl2
“Cisplatin” - a cancer
chemotherapy agent
Co(H2O)62+
Cu(NH3)42+
More examples: natural coordination compounds
Two different kinds of
bonding by N atoms.
Heme = iron (Fe2+) and a porphyrin ring
Hemoglobin and many redox enzymes contain iron-porphyrin complexes
(web; HC examples folder)
Coordination Compounds of Ni2+
[Ni(H2O)6]2+
[Ni(NH3)6]2+
[Ni(H2NCH2CH2NH2)3]2+
Ni(NH3)6]2+
A Ni2+ ion surrounded by six
neutral NH3 ligands
Gives coordination complex ion
with 2+ charge.
Coordination number of Ni = 6.
NH3 , H2O , AND carbon
monoxide (C≡
≡O) are
MONODENTATE LIGANDS.
These are referred to as
“ammine”
“aqua”
“carbonyl”
Bidentate Ligands
Bipyridine (bipy)
Acetylacetone (acac) (1-)
Ethylenediamine (en)
Oxalate (ox) (2-)
Nomenclature
1. Positive ions named 1st , negative ion 2nd
2. Ligand names arranged alphabetically
3. Prefixes -- di, tri, tetra for monodentate ligands
bis, tris, tetrakis for bi- and multi- ligands
4. If M is in cation, name of metal is used
5. If M is in anion, then use suffix -ate
[CuCl4]2- = tetrachlorocuprate
6. Oxidation no. of metal ion indicated as (II) etc
Cis-dichlorobis(ethylenediamine)cobalt(III) chloride
(board)
[Co(H2O)6]2+
Hexaaquacobalt(II)
H2O as a ligand is aqua
[Cu(NH3)4]2+
Tetraamminecopper(II)
Pt(NH3)2Cl2
diamminedichloroplatinum(II)
NH3 as a ligand is ammine
Tris(ethylenediamine)nickel(II)
Pt(
[Ni(NH2C2H4NH2)3]2+
IrCl(CO)(PPh3)2
Carbonylchlorodi(triphenylphosphine)iridium(I)
Structures of Coordination Compounds
Isomers
• Constitutional Isomers
– Same empirical
formula but different
atom-to-atom
connections
• Stereoisomers
– Same atom-to-atom
connections but
different arrangement
in space.
OH2
H 2O
Cl
Cl
Cr
H 2O
Cl
OH2
green
OH2
H 2O
OH2 Cl3
Cr
H 2O
OH2
OH2
violet
Geometric Isomerism
Cis and trans-dichlorobis(ethylenediamine)cobalt(II) chloride
Stereoisomerism
• Chiral (ky’ rul) objects (like certain molecules):
mirror images are not superimposable.
•
example: L, R hands
• Enantiomers: the two non-superimposable mirror
image molecules.
• example: D and L amino acid.
Certain metal coordination complexes.
These are non-superimposable mirror images
[Co(en)(NH3)2(H2O)Cl]2+
See .hin file
The end