Download Chapter 24: Transition Metals Coordination Compounds Part 1

Chapter 24: Transition Metals Coordination Compounds Part 1
Transition Metals
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The transition metals include the d-block, Groups 3-12.
The inner transition metals include the f-block elements.
Many transition metals form beautifully colored solids and solutions.
Electron Configuration Review
• Remember that the valence electrons are the electrons in the highest energy level?
• Although the d-electrons aren’t in the highest energy level, they are very close in energy to the s
electrons in the next higher energy level. Ex: 3d energy level is very close to the 4s energy level.
• What this means is that we can count the valence electrons as the (n-1)d + ns electrons.
• For example Ni has the e- configuration: [Ar]3d84s2 so it has 8+2=10 valence e• What is the e- configuration and # of valence e- for Cu?
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Also, remember that when a transition metal forms an ion, the s electrons are lost first!
So if we form the Ni2+ ion, then the e- configuration for this ion is [Ar]3d8
Furthermore, the Ni2+ ion now only has 8 valence e- (don’t count the lower s and p, just the d)
What is the e- configuration for Cu+ and Cu2+ and how many valence e- do these ions have?
Oxidation States and Coordination Numbers for Transition Metals
• Most transition metals may be found in more than 1 oxidation states, even Ag and Zn, which we
typically think of as having a fixed oxidation state when in ionic compounds.
• What are the oxidation states of the transition metals in the following complexes?
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The above compounds are called coordination compounds or complexes, and they may be neutral or
charged.
In all of them, a metal ion or atom is the central atom, and it is attached to 2 or more surrounding
molecules or ions by covalent bonds (not ionic).
Example: [Ag(NH3)2]+
The covalently attached ions or molecules are called ligands.
The ligand atom which is directly connected to the metal atom/ion is called the ligand donor atom
or just the donor atom.
So in the above, ammonia is the ligand.
If the complex is an ion, like the above, it is written in brackets as shown above.
Complex ions may also form an ionic salt by combining with an oppositely charged ion.
So you could easily form the salt [Ag(NH3)2]Cl. Note how the Cl- anion is outside the brackets.
The coordination number of a coordination compound is simply the number of ligand atoms which
are directly covalently attached to the transition metal atom or ion.
So the coordination number of [Ag(NH3)2]+ and [Ag(NH3)2]Cl are both 2 (note that the Cl-anion is
ignored as it is not covalently attached).
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Transition metals form a wide variety of coordination compounds with coordination numbers from
2-8, but they commonly have 2, 4, or 6 ligands attached.
What are the coordination numbers of the following complexes?
Common Ligands: Monodentate and Polydentate Ligands
• Here are some common ligands:
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Although most of these ligands are what we call monodentate, only attached 1 place to the metal
atom/ion, there are also many polydentate ligands.
Polydentate ligands, like the oxalate ion, C2O42-, attach to the metal atom/ion in 2 or more places, or
on 2 or more ligand donor atoms.
For example, [Zn(oxal)2]2- would look like this:
What about the structure of the more common coordination compounds?
The common geometric shapes and their valence bond theory hybridization for coordination
compounds is as follows:
Nomenclature
• The rules for naming coordination compounds are as follows:
1. If the complex is a salt, name the cation portion first, then the anion.
Ex:
2. When naming a complex ion or a neutral complex, name the ligands first using the appropriate
prefix (di, tri, tetra, etc.), then name the metal. If a ligand is an anion, it name ends in –o (like
chloro or cyano). Specify the metal oxidation # with a Roman numeral inside ( ). If there are
more than 1 different ligand, name them alphabetically, ignoring the prefixes.
3. If the ligand name itself contains a prefix, like ethylenediamine, then put the name inside ( ), and
use one of the following prefixes to specify the number of these ligands: 2 is bis, 3 is tris, 4 is
tetrakis.
Ex:
4. If the complex ion is an anion, give the metal an –ate ending.
Ex:
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Take-Home Problem: See handout.