Transcript Transition Metals and Coordination Chemistry
C h a p t e r
20 Transition Elements and Coordination Chemistry
Why Study Coordinated Complexes of Transition metals?
These compounds are used as catalyst in oxidation of organic compounds and pharmaceutical applications. Chem 1A Review Chapter 20 Slide 2
Order of orbitals (filling) in multi-electron atom 1s < 2s < 2p < 3s < 3p < 4s < 3d < 4p < 5s < 4d < 5p < 6s < 4f< 5d< 6p< 7s< 5f< 6d< 7p Chapter 20 Slide 3
Chapter 20 Slide 4
Electron Configuration and the Periodic Table
4f 5f Chapter 20 Slide 5
Using periodic table write Noble gas notation for the following elements:
a)S [Ne]3s 2 3p 4 [Ar] 4s 2 3d 6 b)Fe c)Se [Ar] 4s 2 3d 10 4p 4 d)Gd [Xe]6s 2 4f 7 5d1
1s < 2s < 2p < 3s < 3p < 4s < 3d < 4p < 5s < 4d < 5p < 6s <
4f< 5d
< 6p< 7s< 5f< 6d< 7p Slide 6
Chapter 20 Slide 7
Electron Configurations Chapter 20 Slide 8
Why Study Coordinated Complexes of Transition metals?
Are used as catalyst in oxidation of organic compounds.
Medicinal applications.
“Cisplatin” - a cancer chemotherapy agent
Chapter 20 Slide 9
Coordination Compounds
Pt(NH 3 ) 2 Cl 2 Co(H 2 O) 6 2+ “Cisplatin” - a cancer chemotherapy agent
Chapter 20
Cu(NH 3 ) 4 2+
Slide 10
[Ni(NH 3 ) 6 ] +2 [Ni(NH 2 C 2 H 4 NH 2 ) 3 ] +2 Coordination Compounds of Ni 2+
Chapter 20 Slide 11
Electron Configurations
Sc
(
Z
= 21): [Ar] 3
d
1 4
s
2
Zn
(
Z
= 30): [Ar] 3
d
10 4
s
2 Chapter 20 Slide 12
Omit 20.2 - 20.4
Coordination Compounds Many
coordination compound
consists of a complex ion.
A
complex ion
contains a central metal cation or more molecules or ions.
bonded to one The molecules or ions that surround the metal in a complex ion are called
ligands
.
A ligand has
at least one
unshared pair of valence electrons H O H • • N H H H • • ••Cl C O Chapter 20 Slide 13
Coordination Compounds The atom in a ligand that is bound directly to the metal atom is the
donor atom
.
O • • N H H H H H Ligands with: one donor atom two donor atoms three or more donor atoms monodentate bidentate polydentate H 2 O, NH 3 , Cl ethylenediamine EDTA The number of donor atoms surrounding the central metal atom in a complex ion is the
coordination number
.
Chapter 20 Slide 14
Coordination Compounds
Coordination Number
: The number of ligand donor atoms that surround a central metal ion or atom.
Chapter 20 Slide 15
Ligands 02 Chapter 20 Slide 16
Ligands 03 Chapter 20 Slide 17
Poly DentateLigands •
EDTA 4 –
is often used to treat heavy metal poisoning such as Hg 2+ , Pb 2+ , and Cd 2+ .
•
EDTA 4 –
bonds to Pb 2+ , which is excreted by the kidneys as [Pb(EDTA)] 2 – .
Chapter 20 Slide 18
Coordination Compounds bidentate ligand • • H 2 N CH 2 CH 2 • • NH 2 polydentate ligand (EDTA) Bidentate and polydentate ligands are called
chelating agents
Chapter 20 Slide 19
Naming coordinated complex compounds What is the Oxidation Numbers of Cu?
+2
Knowing the charge on a complex ion and the charge on each ligand, one can determine the oxidation number for the metal.
Chapter 20 Slide 20
Oxidation Number Rules Rule 1 2 3 Applies to Elements Statement The oxidation number of an atom in an element is zero.
Monatomic ions Oxygen The oxidation number of an atom in a monatomic ion equals the charge of the ion.
The oxidation number of oxygen is –2 in most of its compounds. (An exception is O in H 2 O 2 and other peroxides, where the oxidation number is – 1.) Chapter 20 Slide 21
Oxidation Number Rules Rule 4 5 6 Applies to Hydrogen Statement +1, it will be -1 when hydrogen comes with metal. NaH Halogens Compounds and ions Fluorine is –1 in all its compounds. Each of the other halogens is –1 in binary compounds unless the other element is oxygen.
The sum of the oxidation numbers of the atoms in a compound is zero. The sum in a polyatomic ion equals the charge on the ion.
Chapter 20 Slide 22
What is the charge on the following Complex, If the Oxidation number of Cr is +3?
Or, knowing the oxidation number on the metal and the charges on the ligands, one can calculate the charge on the complex ion.
Chapter 20 Slide 23
What are the oxidation numbers of the metals in K[Au(OH) 4 ] and [Cr(NH 3 ) 6 ](NO 3 ) 3 ?
OH has charge of -1 K + has charge of +1 ? Au + 1 + 4x(-1) = 0 Au = +3 NO 3 has charge of -1 NH 3 has no charge ? Cr + 6x(0) + 3x(-1) = 0 Cr = +3 Chapter 20 Slide 24
Oxidation States of the 1 st Row Transition Metals ( most stable oxidation numbers are shown in red ) Chapter 20 Slide 25
Learning Check A complex ion contains a Cr molecules and two Cl – 3+ bound to four H 2 O ions. Write its formula.
+1 Chapter 20 Slide 26
Coordination Sphere
•
Coordinate bond:
H Ag + (aq) + 2 H H H H H Ag H H H + •
Coordination Sphere:
is the central metal and surrounding ligands. The square brackets separate the complex from counter ions such as SO 4 2 – .
[Ag(NH 3 ) 2 ] 2 SO 4 Chapter 20 Slide 27
Geometry of Coordination Compounds Coordination number 2 4 6 Structure Linear
Tetrahedral or Square planar (mostly d 8 )
Octahedral Chapter 20 Slide 28
Coordination Number of 7&8 • Geometry Pentagonal bipyramid Coordination Number of 7 Chapter 20 Hexagonal bipyramid Coordination Number of 8 Slide 29
Coordination Compounds •
Geometries:
Chapter 20 Slide 30
Nomenclature
Co(H 2 O) 6 2+ Hexaaquacobalt(II) H 2 O as a ligand is aqua Cu(NH 3 ) 4 2+ Tetraamminecopper(II) Pt(NH 3 ) 2 Cl 2 NH 3 diamminedichloroplatinum(II) as a ligand is ammine Systematic naming specifies the type and number of ligands, the metal, and its oxidation state.
Chapter 20 Slide 31
Ligand’s Names 01 Chapter 20 Slide 32
Chapter 20 Slide 33
Nomenclature Chapter 20 Slide 34
Nomenclature •
Systematic naming follows IUPAC rules:
• If compound is a salt, name cation first and then the anion , just as in naming simple salts.
• In naming a complex ion or neutral complex, name ligands first and then the metal .
• If the complex contains more than one ligand of a particular type, indicate the number with the appropriate Greek prefix:
di –, tri–, tetra–, penta–, hexa–
.
Chapter 20 Slide 35
Nomenclature • If the name of a ligand itself contains a Greek prefix, (ethylene di amine or
tri phenylphosphine
) put the ligand name in parentheses and use:
bis (2), tris (3), or tetrakis (4)
.
• Use a Roman numeral in parentheses, immediately following the name of the metal, to indicate the metal’s oxidation state .
• In naming the metal, use the ending
–ate
if metal is in an anionic complex.
Chapter 20 Slide 36
Name the following Complexes:
Pt(
Tris(ethylenediamine)nickel(II) [Ni(NH 2 C 2 H 4 NH 2 ) 3 ] 2+ IrCl(CO)(PPh 3 ) 2 Carbonylchlorobis(triphenylphosphine)iridium(I)
Chapter 20 Slide 37
What is the systematic name of [Cr(H 2 O) 4 Cl 2 ]Cl ?
tetraaquadichlorochromium(III) chloride Write the formula of tris(ethylenediamine)cobalt(II) sulfate [Co(en) 3 ]SO 4 Chapter 20 Slide 38
Constitutional Isomerism 1. Constitutional Isomers:
Have different bonds among their constituent atoms.
•
Ionization Isomers :
[Co(NH 3 ) 5 Br]SO 4 (violet compound with Co –Br bond), [Co(NH 3 ) 5 SO 4 ]Br (red compound with Co –SO 4 bond).
•
Linkage Isomers
form when a ligand can bond through two different donor atoms. Consider [Co(NH 3 ) 5 NO 2 ] 2+ which is yellow with the Co –NO 2 bond and red with the Co –ONO bond.
Chapter 20 Slide 39
Linkage Isomerism H H 3 3 N N NH 3 Co 2+ NO 2 NH 3 NH 3 sunlight H H 3 3 N N NH 3 Co NH 3 ONO NH 3 2+ Such a transformation could be used as an energy storage device.
Chapter 20 Slide 40
2 .Stereoisomers •
Geometric Isomers of Pt(NH 3 ) 2 Cl 2 :
In the
cis isomer,
atoms are on the
same
side. In the
trans isomer,
atoms are on
opposite
sides.
DNA-damaging antitumor agents Inactive Slide 41
2 .Stereoisomers
Geometric Isomers
have the same connections among atoms but different spatial orientations of the metal –ligand bonds.
a) cis isomers
have identical ligands in
adjacent corners
of a square.
b) trans isomers
have identical ligands
across the corners
from each other.
Chapter 20 Slide 42
Isomers •
Geometric Isomers of [Co(NH 3 ) 4 Cl 2 ]Cl:
Chapter 20 Slide 43
Enantiomers Chapter 20 Slide 44
Enantiomers •
Enantiomers are stereoisomers of molecules or ions that are
nonidentical mirror images
of each other.
•
Objects that have “handedness” are said to be
chiral
, and objects that lack “handedness” are said to be
achiral
.
• An object or compound is
achiral symmetry plane
if it has a cutting through the middle.
Chapter 20 Slide 45
Enantiomers Chapter 20 Slide 46
© 2003 John Wiley and Sons Publishers Unpolarized light.
Chapter 20 Slide 47
plane-polarized light
© 2003 John Wiley and Sons Publishers Plane-polarized light.
Chapter 20 Slide 48
© 2003 John Wiley and Sons Publishers Reflected glare is plane-polarized light.
Chapter 20 Slide 49
© 2003 John Wiley and Sons Publishers Polarizing sunglasses versus glare.
Chapter 20 Slide 50
© 2003 John Wiley and Sons Publishers The effect of polarizing lenses on unpolarized light.
Chapter 20 Courtesy Andy Washnik Slide 51
plane-polarized light
Chapter 20 Slide 52
Enantiomers and Molecular Handedness Chapter 20 Slide 53
Enantiomers
Enantiomers reaction with other chiral substances and their effect on have identical properties except for their
plane-polarized light
.
•
Enantiomers are often called
optical isomers
; their effect on plane-polarized light can be measured with a
polarimeter
.
Chapter 20 Slide 54
Enantiomers
•
Plane-polarized light
is obtained by passing ordinary light through a polarizing filter .
• In a polarimeter the plane-polarized light is passed through a chiral solution and the polarization plane measured with an analyzing filter .
• If the plane rotates to the right it is
dextrorotatory
.
• If the plane rotates to the left it is
levorotatory
.
• Equal amounts of each are
racemic
.
Chapter 20 Slide 55
Isomers 01 Chapter 20 Slide 56
[Co(NH 3 ) 5 Br]SO 4 (violet), [Co(NH 3 ) 5 SO 4 ]Br (red ).
H 3 N H 3 N NH 3 Co 2+ NO 2 NH 3 NH 3 sunlight H 3 N H 3 N NH 3 Co ONO NH 3 NH 3 2+
See next slide for Diastereoisomers Slide 57
Diasteromers Chapter 20 Slide 58
Bonding in Complexes •
Bonding Theories
attempt to account for the color and magnetic properties of transition metal complexes.
01 Co 2+ Ni 2+ Cu 2+ Zn 2+ Chapter 20 • Solutions of [Ni(H 2 O) 6 ] 2+ , [Ni(NH 3 ) 6 ] 2+ , & [Ni(en) 3 ] 2+ Slide 59
Color of Transition Metal Complexes D
E
=
E
2 -
E
1 =
h
n =
hc
l or l =
hc
D
E
Chapter 20 Slide 60
Color of Transition Metal Complexes Chapter 20 Slide 61
Color of Transition Metal Complexes Chapter 20 Slide 62
Bonding in Complexes: Valence Bond Theory Chapter 20 Slide 63
Bonding in Complexes: Which empty orbital is metal using for bonding S, p, d or f ?
Chapter 20 Slide 64
Hybridization and
sp
3 Hybrid Orbitals
How can the bonding in CH 4 be explained?
2
4 valence electrons unpaired electrons Chapter 20 Slide 65
Hybridization and
sp
3 Hybrid Orbitals
How can the bonding in CH 4 be explained?
4
4 valence electrons unpaired electrons Chapter 20 Slide 66
Hybridization and
sp
3 Hybrid Orbitals
How can the bonding in CH 4 be explained?
4
nonequivalent
orbitals Chapter 20 Slide 67
Hybridization and
sp
3 Hybrid Orbitals
How can the bonding in CH 4 be explained?
Chapter 20 4
equivalent
orbitals Slide 68
Hybridization and
sp
3 Hybrid Orbitals Chapter 20 Slide 69
Hybridization and
sp
3 Hybrid Orbitals Chapter 20 Slide 70
Other Kinds of Hybrid Orbitals Chapter 20 Slide 71
Hybrid Orbitals in Coordinated Complexes We should look at magnetic property of the complex to see if they are
high or low spin
. Then we could decide whether they are using d 2 sp 3 or sp 3 d 2 hybrid Slide 72
The octahedral d 2 sp 3 and sp 3 d 2 Chapter 20 Slide 73
Square Planar geometry of four dsp 2 Chapter 20 Slide 74
Bonding in Complexes: Valence Bond Theory Experimental results: High Spin Chapter 20 Slide 75
Bonding in Complexes: Valence Bond Theory Experimental results: Low Spin Chapter 20 Slide 76
High- and Low-Spin Complexes [Co(CN) 6 ] 3 High spin:
Maxium number of unpaired electron, Paramagnetic
Low spin :
Minimum number of unpaired electron
Chapter 20 Slide 77
Crystal Field Theory
Crystal Field Theory
: Effect of charges of ligand on transition metal d-electrons.
A model that views the bonding in complexes as arising from electrostatic interactions and considers the effect of the ligand charges on the energies of the metal ion
d
orbitals.
Chapter 20 Slide 78
Crystal Field Theory
Octahedral Complexes
Directed
between
ligands Directed
at
ligands Chapter 20 Slide 79
Crystal Field Theory
Octahedral Complexes
Chapter 20 Slide 80
Crystal Field Theory
Octahedral Complexes
[Ni(X) 6 ] 2+ X=H 2 O, NH 3 , and ethylenediamine (en) Chapter 20 (red-violet) Slide 81
[Ti(H 2 O) 6 ] 3+ Chapter 20 Slide 82
Crystal Field Theory
Octahedral Complexes
The crystal field splitting changes depending on nature of the legand.
[Ni(X) 6 ] 2+ X=H 2 O, NH 3 , and ethylenediamine (en) Chapter 20 Slide 83
The absorption maximum for the complex ion [Co(NH 3 ) 6 ] 3+ occurs at 470 nm. What is the color of the complex and what is the crystal field splitting in kJ/mol?
D E =
h
n =
hc
l DE (kJ/mol) ?
= 255 kJ/mol Chapter 20 = 4.23 x 10 -19 J Slide 84