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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

is methane a molecule
Okologwu Reply
yes
Miriam
no
rilwan
calculations for solubility
malachi Reply
Whats d IUPAC Numenclature of bromine
Emmanuel Reply
The common name is therefore propyl bromide . For the IUPAC name , the prefix for bromine (bromo) is combined with the name for a three-carbon chain (propane), preceded by a number identifying the carbon atom to which the Br atom is attached, so the IUPAC name is 1-bromopropane.
crystal
What is Quantum number
Derick Reply
what are the chemical properties of group IIA Element and their atomic structure?
NATHAN Reply
What is mixture
Azeez Reply
A mixture is a mix of substances that can be separated
Lillie
what is quantum number
Baba Reply
Hmm
kedis
I suck at chemistry I need a tutor
kedis
h20 hydrates, nitrogen/dry ice lowers pressure similar to space environment when heated at what location/temp.? +or-, expect location (xyz)
Brian
hey kedis,never say that u suck,u don't,all u need is to calm down,get the book and get the points,no need to read it word by word or a-z. ur good bro,u r veeeery intelligent
UDUJI
awwwww
Cereal
what's neuron?
Kelvin Reply
neuron or neutron?
John
cell of the nerve
Kamaluddeen
neuron
rilwan
prepare a solution of 1m iodine in 250mls of water
Dj Reply
Really
Wisdom
Hiiii am new here
Wisdom
Really
Wisdom
WHAT IS CHEMISTRY?
RJ
Chemistry is the study of matter
Wisdom
chemistry is the study of matter and changes it undergoes
Mercy
what is equilibrium
Fatai Reply
what is biology
Fatai
biology is said to be the science of studying life and living organism including theirs physical structure,chemical processes, molecular interaction development and evolution
David
atomic number of sodium
bose
that'll be 11
Kamaluddeen
ok
bose
anymore questions 😁
Franklin
re u writing jamb
bose
please, how man Bond are present when a methane under goes a complete combustion
moses Reply
Combustion of Methane The reactants are on the left side of the equation and the products are on the right. In the reaction, the bonds in the methane and oxygen come apart, the atoms rearrange and then re-bond to form water and carbon dioxide.
saidi
how is ethanol produced using ethene
Glory
Ethanol is manufactured by reacting ethene with steam. The reaction is reversible, and the formation of the ethanol is exothermic. Only 5% of the ethene is converted intoethanol at each pass through the reactor
saidi
Ethanol can be made by reacting ethene (from cracking crude oil fractions) with steam. A catalyst of phosphoric acid is used to ensure a fast reaction. Notice that ethanol is the only product. The process is continuous – as long as ethene and steam are fed into one end of the reaction vessel, ethano
saidi
the mole concerpt and its tricks
Mary Reply
what are atoms
ola Reply
the individual elements of matter.
Reginald
tiny particles that make up a all matter.
Reginald
smallest particles of an element
Osuji
What is the meaning of hybridization
JOSEPH Reply
Differentiate between latent heat and specific latent heat of fusion and vaporization
Amos Reply
Ans: The amount of heat energy released or absorbed when a solid changing to liquid at atmospheric pressure at its melting point is known as the latent heat of fusion. while Vaporization of an element or compound is a phase transition from the liquid phase to vapor.
Acquah

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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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