Download Chapter 25 Transition Metals and Coordination Compounds Part 1

Chapter 25 Transition Metals and Coordination Compounds Part 1
Introduction
The transition elements are defined as: those metallic elements that have a
partially but incompletely filled d subshell or easily give rise to common
ions that have incompletely filled d subshells.
Even though Cd, Zn, & Hg are in the d-block, they are not transition elements
in the strict sense. Their chemistry will not be represented by our discussions.
The f-block elements are sometimes referred to as the
We will only be studying the ___________ elements
Electron Configuration Review
s subshell fills first (lower energy); d subshell filled according to Hund's rule.
1. Add one electron to each of the five d orbitals before adding a 2nd electron.
Sc
Ti
V
Cr
Mn
[Ar]4s23d1
[Ar]4s23d2
[Ar]4s23d3
[Ar]4s23d4
[Ar]4s23d5
Fe
[Ar]4s23d6
Co
Ni
Cu
[Ar]4s23d7 [Ar]4s23d8
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[Ar]4s23d9
Zn
[Ar]4s23d10
Electron configurations depend on both ___________
and ______________________________________________.
1. If two valence subshells have similar energies, can't always predict the
configurations.
2. Exceptions from the expected orbital filling pattern result in either halffilled or completely filled subshells.
3. Five of the 19 exceptions:
a. Group 6: Cr: [Ar] 4s13d5
b. Group 11: Cu: [Ar] 4s13d10
Transition-metal cations.
1. Valence electrons typically occupy the d orbitals.
(s shell is emptied before d.)
Example: Fe = [Ar]4s23d6
Fe2+ =
Fe3+ =
Oxidation States
Determine the oxidation number for the transition metal in each of the following:
All charge add to 0 for neutral compounds or to the ion charge for an ion.
a)
CoSO4 =
c) K3[Cr(CN)6] =
b) [PtCl4]2- =
d) [Fe(H2O)5(OH)]2+ =
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Oxidation States of Transition
Elements
Large variety of oxidation states.
First series (Period 4) form __
oxidation state (except Sc).
Due to loss of the two ___
electrons.
First series - can also lose ___ electrons.
3d and 4s energies are similar
Highest oxidation state for the group 3B-7B metals is the ______________ .
Common oxidation states are in bold face.
1. Corresponds to loss of all the valence s and d electrons.
2. Later transition metals - loss of all valence electrons is prohibited by the
increasing value of ______.
Coordination Compounds
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___________ - the molecule or ions that surround the central metal ion
in a complex: the ___________!
(In Latin, ligare means to bind.)
___________ - the atoms attached directly to the metal ion.
___________________ - the number of ligand donor
atoms that surround a central metal ion in a complex.
- Most common coordination numbers: ____ and ____.
__________ of metal complex is determined by the metal ion's
coordination number. (i.e. tetrahedral, octahedral, etc.)
_________________ – the central metal cation plus
the ligands covalently bonded to it.
- It is the part inside the [ ] of the formula
- Not the part outside the [ ] that is ionically bonded!
Covalent bonding –
monodentate – donates
bidentate – donates
pair of e-
pairs of e-
tetradentate – donates
pairs of e-
hexadentate – donates
pairs of e-
polydentate – donates more than 2 pairs of e25-4
Geometries and hybridizations (using VSEPR theory) for common coordination
number are:
Coordination #
Hybridization
Geometry
Example
2
sp
linear
[Ag(NH3)2]+
4
sp3
tetrahedral
[Zn(CN)4]2-
4
dsp2 of sp2d
square planar
[Ni(CN)4]2-
5
dsp3
trigonal bipyrimidal
[CuCl5]3-
5
d2sp2
square pyramidal
[Ni(CN)5]3-
6
d2sp3 or sp3d2
octahedral
[Fe(CN)6]4-
skip naming coordination compounds section
Some Important Ammine Complexes
 Complex ions are made by NH3 molecules bonded to metal ions.
 With a little NH3(aq) (aka NH4OH) is added, the hydroxide ppt will form.
 If more NH3(aq) is added, a complex ion will form with the metal ion.
For example, Cu and Fe both react with aqueous NH3 to form hydroxides:
Cu2+(aq) + 2 NH3(aq) + 2 H2O(l) 
Fe3+(aq) + 3 NH3(aq) + 3 H2O(l) 
Copper will form a complex ion while iron will not.
Cu(OH)2(s) + 4 NH3(aq) 
Fe(OH)3(s) + NH3(aq) 
Some metal ions that form soluble ammine complexes in an excess of NH3 are:
Cu+, Ag+ (with 2 NH3 molecules)
Cu2+, Zn2+, Cd2+, Hg2+ (with 4 NH3 molecules)
Co2+, Co3+, Ni2+, (with 6 NH3 molecules)
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Structure and Isomerization
Isomers –
Structural Isomers – atoms are connected to one another in different ways
(a.k.a. constitutional isomers)
1. _________________________ - arise when a ligand can bond to a metal through
either of two different donor atoms.
[Co(NH3)5(ONO)]2+
(NO2- ligand bonds through the ___________ atom)
[Co(NH3)5(NO2)] 2+
(NO2- ligand bonds through the ___________ atom)
2. ______________________ - isomers that differ in the anion that is bonded to
the metal ion. Mistakenly called coordination isomers in TRO!!!
[Pt(NH3)4Cl2]Br2
__________ as counter ion
[Pt(NH3)4Br2]Cl2
__________ as counter ion
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Also can have one of each
inside the coordination sphere
3. ______________________ – special case of ionization isomers where water
molecules are switch between inside and outside the coordination sphere.
[Cr(H2O)6]Cl3
6 waters bonded to metal ion
[Cr(H2O)5Cl]Cl2·H2O
5 waters bonded to metal ion
[Cr(H2O)4Cl2]Cl·2H2O
5 waters bonded to metal ion
4. ______________________ – denote an exchange of ligands between the
coordination sphere of the cation and the anion
[Pt(NH3)4][PtCl6]
[Pt(NH3)4Cl2][PtCl4]
2 chlorides moved from the anion to the cation
vs
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Stereoisomers – atoms have the same connectivities but different spatial
arrangement
Note: Complexes with only simple ligands can occur as stereoisomes only if they have
coordination number > __.
1. __________________________ (a.k.a Diastereoisomers)
relative orientations of their metal-ligand bonds.
- have different
a) ____________________
Descriptions
cis isomer - identical ligands occupy adjacent corners of the square in a square
planar complex
trans isomer - identical ligands are across from one another in a square planar
complex
They are different compounds with different properties.
Note: no cis-trans isomers exist for four coordinate tetrahedral complexes
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Octahedral cis-trans isomers of the type MA2B4. Two “A” ligands can be
either on adjacent or on opposite corners of the octahedron.
b) Octahedral Fac-mer isomers These occur in octahedral complexes with the
general formula MA3B3.
____ isomer – The three identical ligands all are on the same _______.
____ isomer – The three identical ligands all lie in a single line around the
_______________.
Two such ions are shown for the ion [Pt(NH3)3Cl3]+
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2. Optical Isomers (or enantiomers)
 Non-superimposable mirror images
 The molecule is said to be ________
 Chiral compounds interact with polarized light.
The dextrorotatory isomer rotates plane-polarized light to the _______.
(i.e. the right-handed isomer)
The levorotatory isomer rotates plane-polarized light to the _______.
(i.e. the left-handed isomer.
Optically active compounds do NOT have a
____________________.
The molecule to the left (where all 3 pairs are cis) can create a
pair of optical isomers.
For a tetrahedral molecule to show optical isomerism, it must
have a central atom with __ different atoms attached to it.
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