Transcript Metallurgy and the Chemistry of Metals

The Chemistry of
Coordination Compounds
Chapter 20
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What is a transition metal?
Transition metals have incompletely filled d subshells or
produce ions with incompletely filled d subshells.
This is responsible for many of the properties of
transition metals including color, catalytic activity,
formation of paramagnetic compounds, and the
tendency to form complex ions.
The Transition Metals
20.1
Is zinc a transition metal?
Explain your answer.
Write out the electronic
structure of Zn and of Zn2+
Electron Configurations and Other Properties of the First-Row Transition Metals
20.1
Physical Properties of Elements K to Zn
20.1
Oxidation States of the 1st Row Transition Metals
20.1
Ionization Energies for the 1st Row Transition Metals
20.1
General Properties of Transition Metals
Small atomic radii and close packing—strong
metallic bonds
Transition metals have…
• Higher ________________________
• Higher ________________________
• Higher ________________________
• Higher ________________________
• Higher ________________________
…than _________________________
p.650
Coordination Compounds
A ________________________ typically consists of a complex
ion and a counter ion.
A ________________________ contains a central metal cation
bonded to one or more molecules or ions.
The molecules or ions that surround the
metal in a complex ion are called _______.
H
H
H H H
••
Cl
••
-
C
••
O
••
••
••
N
••
A ligand has ______________ unshared
pair of valence electrons
O
pp.653ff
20.3
Coordination Compounds
The atom in a ligand that is bound directly to the metal atom is
the _________________________.
••
N
O
H
H
H H H
The number of donor atoms surrounding the central metal atom
in a complex ion is the _______________________.
Ligands with:
one donor atom
two donor atoms
_____________
H2O, NH3, Cl_____________ ethylenediamine
three or more donor atoms _____________
EDTA
20.3
Coordination Compounds
____________ ligand
••
H2N
CH2
CH2
••
NH2
____________ ligand
(EDTA)
Bidentate and polydentate ligands are called ______________
20.3
Some common ligands
20.3
What are the oxidation numbers of the metals in
K[Au(OH)4]
and of
[Cr(NH3)6](NO3)3 ?
OH- has charge of ___
NO3- has charge of __
K+ has charge of ___
NH3 has no charge
? Au + __ + (__x-__) = 0
Au = +___
? Cr + (__x__) + (__x-__) = 0
Cr = ___
Ex. 20.1, p.655
20.3
Naming Coordination Compounds
•
The cation is named before the anion.
•
Within a complex ion, the ligands are named first in
________________ order and the metal atom is named last.
•
The names of anionic ligands end with the letter o. Neutral
ligands are usually called by the name of the molecule. The
exceptions are H2O (aquo), CO (carbonyl), and NH3 (amine).
•
When several ligands of a particular kind are present, the
Greek prefixes di-, tri-, tetra-, penta-, and hexa- are used to
indicate the number. If the ligand contains a Greek prefix,
use the prefixes bis, tris, and tetras to indicate the number.
•
The oxidation number of the metal is written in Roman
numerals following the name of the metal.
•
If the complex is an ion, its name ends in –ate.
20.3
Names of Common Ligands in Coordination Compounds
20.3
Names of Anions
Containing Metal Atoms
What is the systematic name of
[Cr(H2O)4Cl2]Cl ?
________________________________
Write the formula of
tris(ethylenediamine)cobalt(II) sulfate
________________________________
20.3
Structure of Coordination Compounds
Coordination number
2
Structure
Linear
4
Tetrahedral or Square planar
6
Octahedral
20.4
Structure of Coordination Compounds
___________________ are compounds that are made up of
the same types and numbers of atoms bonded together in the
same sequence but with different spatial arrangements.
___________________ are stereoisomers that cannot be
interconverted without breaking a chemical bond.
cis-[Pt(NH3)2Cl2]
trans-[Pt(NH3)2Cl2]
20.4
Structure of Coordination Compounds
cis-[Co(NH3)4Cl2]
trans-[Co(NH3)4Cl2]
Are these
additional
geometric
isomers of
[Co(NH3)4Cl2]?
20.4
Structure of Coordination Compounds
_________________ are non-superimposable mirror images.
cis-[Co(en)2Cl2]
trans-[Co(en)2Cl2]
_________________
_________________
____________
____________
20.4
Structure of Coordination Compounds
_______________________
are optically active.
20.4
_________________________
– rotates plane polarized light to the right
_________________________
– rotates plane polarized light to the left
_________________________
rotate plane polarized light by the same
amount, but in opposite directions
_________________________
– an equimolar mixture of enantiomers
Coordination compounds are used in:
___________ – extracting gold and silver, purifying nickel
___________ – treating lead poisoning and cancer
___________ – identification of certain chemicals
___________ – largely banned from modern detergents
because the phosphates caused
eutrophication of lakes
_________ _________ _________ explains
the bonding of complex ions in terms of two
electrostatic forces
1. _________ between the positive metal ion
and the negatively charged ligand or the
negatively charged end of a polar ligand
2. _________ between the electron lone pairs
on the ligands and the d orbitals of the metals
pp.659ff
Bonding in Coordination Compounds
All equal in energy in the absence of _____________ !
20.5
Bonding in Coordination Compounds
Isolated
transition metal
atom
Bonded transition
metal atom
As a result of these two metal-ligand electrostatic interactions,
the 5 d orbitals in an octahedral complex are split between two
sets of energy levels: a higher level with two orbitals and a lower
level with three levels. Crystal field splitting (D) . p.659
20.5
Bonding in Coordination Compounds
Isolated
transition metal
atom
Bonded
transition metal
atom
____________ ____________ ____________ (D) is the
energy difference between two sets of d orbitals in a metal
atom when ligands are present. And…
20.5
Bonding in Coordination Compounds
D = hn
20.5
The absorption maximum for the complex ion [Co(NH3)6]3+
occurs at 470 nm. What is the color of the complex and
what is the crystal field splitting in kJ/mol?
Absorbs blue, will appear orange.
(6.63 x 10-34 J s) x (3 x 108 m s-1)
hc
D = hn =
=
= __________ J
l
-9
470 x 10 m
D (kJ/mol) = 4.23 x 10-19 J/atom x 6.022 x 1023 atoms/mol
= ___________ kJ/mol
20.5
Bonding in Coordination Compounds
Spectrochemical Series
I- < Br- < Cl- < OH- < F- < H2O < NH3 < en < CN- < CO
Weak field ligands
_____________ D
Strong field ligands
_____________ D
20.5
Bonding in Coordination Compounds
20.5
Reactions of coordination compounds
Coordination compounds typically
undergo ligand exchange
(a/k/a ligand substitution) in solution