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By the end of this section, you will be able to:
  • List the defining traits of coordination compounds
  • Describe the structures of complexes containing monodentate and polydentate ligands
  • Use standard nomenclature rules to name coordination compounds
  • Explain and provide examples of geometric and optical isomerism
  • Identify several natural and technological occurrences of coordination compounds

The hemoglobin in your blood, the chlorophyll in green plants, vitamin B-12, and the catalyst used in the manufacture of polyethylene all contain coordination compounds. Ions of the metals, especially the transition metals, are likely to form complexes. Many of these compounds are highly colored ( [link] ). In the remainder of this chapter, we will consider the structure and bonding of these remarkable compounds.

This figure shows six containers. Each is filled with a different color liquid. The first appears to be clear; the second appears to be purple; the third appears to be red; the fourth appears to be teal; the fifth appears to be blue; and the sixth also appears to be clear.
Metal ions that contain partially filled d subshell usually form colored complex ions; ions with empty d subshell ( d 0 ) or with filled d subshells ( d 10 ) usually form colorless complexes. This figure shows, from left to right, solutions containing [ M (H 2 O) 6 ] n+ ions with M = Sc 3+ ( d 0 ), Cr 3+ ( d 3 ), Co 2+ ( d 7 ), Ni 2+ ( d 8 ), Cu 2+ ( d 9 ), and Zn 2+ ( d 10 ). (credit: Sahar Atwa)

Remember that in most main group element compounds, the valence electrons of the isolated atoms combine to form chemical bonds that satisfy the octet rule. For instance, the four valence electrons of carbon overlap with electrons from four hydrogen atoms to form CH 4 . The one valence electron leaves sodium and adds to the seven valence electrons of chlorine to form the ionic formula unit NaCl ( [link] ). Transition metals do not normally bond in this fashion. They primarily form coordinate covalent bonds, a form of the Lewis acid-base interaction in which both of the electrons in the bond are contributed by a donor (Lewis base) to an electron acceptor (Lewis acid). The Lewis acid in coordination complexes, often called a central metal    ion (or atom), is often a transition metal or inner transition metal, although main group elements can also form coordination compounds . The Lewis base donors, called ligands , can be a wide variety of chemicals—atoms, molecules, or ions. The only requirement is that they have one or more electron pairs, which can be donated to the central metal. Most often, this involves a donor atom    with a lone pair of electrons that can form a coordinate bond to the metal.

Three electron dot models are shown. To the left, a central C atom is shown with H atoms bonded above, below, to the left, and to the right. Between the C atom and each H atom are two electron dots, one red, and one black, next to each other in pairs between the atoms. The second structure to the right shows N superscript plus sign followed by a C l atom in brackets. This C l atom has pairs of electron dots above, below, left, and right of the element symbol. A single electron dot on the left side of the symbol is shown in red. All others are black. Outside the brackets to the right, a negative sign appears as a superscript. The third structure on the far right has a central S c atom. This atom is surrounded by six pairs of evenly-spaced electron dots. These pairs of dots are positioned between the S c atom and each of the O atoms from six H subscript 2 O molecules. This entire structure is within brackets to the right of which is the superscript 3 plus.
(a) Covalent bonds involve the sharing of electrons, and ionic bonds involve the transferring of electrons associated with each bonding atom, as indicated by the colored electrons. (b) However, coordinate covalent bonds involve electrons from a Lewis base being donated to a metal center. The lone pairs from six water molecules form bonds to the scandium ion to form an octahedral complex. (Only the donated pairs are shown.)

The coordination sphere    consists of the central metal ion or atom plus its attached ligands. Brackets in a formula enclose the coordination sphere; species outside the brackets are not part of the coordination sphere. The coordination number    of the central metal ion or atom is the number of donor atoms bonded to it. The coordination number for the silver ion in [Ag(NH 3 ) 2 ] + is two ( [link] ). For the copper(II) ion in [CuCl 4 ] 2− , the coordination number is four, whereas for the cobalt(II) ion in [Co(H 2 O) 6 ] 2+ the coordination number is six. Each of these ligands is monodentate    , from the Greek for “one toothed,” meaning that they connect with the central metal through only one atom. In this case, the number of ligands and the coordination number are equal.

Questions & Answers

What are molecules
Ruth Reply
a group of atoms bonded together, representing the smallest fundamental unit of a chemical compound that can take part in a chemical reaction
were is ruth
what is partial pressure law
Mokutmfon Reply
what is the structural formular for 2,3-dimethylbutane?
Mercy Reply
name the following compound (COOH)2
CH3-CH(CH3)-CH(CH3)-CH3 this is 2,3-dimethylbutane
(COOH)2 is oxalic acid
what is chemistry
Boris Reply
chemistry is the study of chemical reactions
Chemistry is the study of matter, its properties, how and why substances combine or separate to form other substances, and how substances interact with energy.
chemistry is the study of matter, it's properties and composition
hello Lucy
hello boris nice to meet u all
lucy were you from and what grade are you doing
am from Abuja and am in ss1
ss1 some one translate that for me we use grades in my country
maybe grade 9
okay am a chemistry and biology teacher from Zambia
should be grade 10 I think
oh okay hello
thats good Mr mwanza
harriet you in grade what
GCE 12
from where
text me on whats up
we help each other
yes sir
me ss2
so are a final year student
wow I didn't know it chat group
What is the chemical formula for alcohol? is the chemical formula for alcohol?
Grant Reply
20 element are what element?
Eric Reply
What is Chemistry?
Esther Reply
studying about chemical reactions
You are right Vengada
studying about the rate of chemical is ?
Chemistry is the branch of sciences dealing with the composition of substances and their properties and reaction.
chemical reaction is the process in which one or more chemical substances react with other chemical substance and converted one or more different substances.
what is isotopy
Isotopy is one of two or more atoms having the same atomic numbers but different mass number.
Molar mass of Chlorine
Sakyi Reply
molar mass of chlorine 35.5
what is chemistry
Raphael Reply
Molar mass of Chlorine atom
chem is the study of structure, properties of matter and changes that matter undergo
m.m of Cl is 35.5
what is an acid
Harriet Reply
example, HCl, H2SO4, HNO3
an acid is a substance that dissolves in water to give hydrogen oins as the only negatively charged ions
Galina is correct those are some examples of acids , others are ethanedioic acid, ethanoic acid , methanoic acid ma ans above is tha definition of an acid
An acid is a substance with particular chemical properties including litmus red, neutralizing alkalis and dissolving some metals.
Shelia is also right 💯💯
what is hydrocarbon?
is a group of carbon atoms that is bonded with an alkyl group eg methyl butane
A hydrocarbon is a compound that contains only hydrogen and carbon atoms
it means only carbon and hydrogen atoms are bonded..
when ammonia and hydrogen ion bond together to form ammonium ion the bond formed is called
Gladys Reply
coordinate bond
its called Dative covalent bond\ coordinate bond..
what are the factors affecting chemical equilibrium
what IS the meaning of esterification
Nad Reply
it is converting a compound by replacing the hydrogen of an acid by an alkyl other organic group maybe caboxyl
It is the method in which esters are produced. When alcohols are treated with carboxylic acids in presence of an acid,sweet smelling esters are produced.
thermodynamic first law
Rathika Reply
The first law of thermodynamics, also known as Law of Conservation of Energy, states that energy can neither be created nor destroyed; energy can only be transferred or changed from one form to another
what is any isotope
Wesley Reply
An isotope is atoms of a single element(same atomic number) that differ in the number of neutrons in their nuclei (different masses)
what is the difference between covalent bonding and ionic bonding
A covalent bond is where sharing of electrons is between atoms or two non metals e.g chlorine and another chlorine atom whereas an ionic bond is formed between a metal and a non-metal such as magnesium metal and chlorine non-metal giving us MgCl2
am new here someone should help me with balance equation ,I don't know how to balance equation

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Source:  OpenStax, Chemistry. OpenStax CNX. May 20, 2015 Download for free at http://legacy.cnx.org/content/col11760/1.9
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