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Three structures are shown. In a, a central A g atom has N atoms bonded to the left and right as indicated by line segments. Three H atoms are similarly bonded to each N atom extending out and up, out to the side, and out and below each N atom. The structure is enclosed in brackets with a superscript plus sign to the right of the brackets. In b, a C u atom is at the center of the structure. Line segments indicate bonds to two C l atoms, one above and the other below and to the left of the central atom. To the right, a dashed wedge, narrow toward the C u atom and widening toward a C l atom, is shown at the right side of the central C u atom. A solid wedge is similarly directed toward a C l atom below and slightly right of the central C u atom. This structure is enclosed in brackets with a superscript 2 negative sign present to the right of the brackets. In c, a structure is shown with a central C o atom. From the C o atom, line segments indicate bonds to H subscript 2 O molecules above and below the structure. Above and to both the right and left, dashed wedges indicate bonds to two H subscript 2 O molecules. Similarly, solid wedges below to both the right and left indicate bonds to two more H subscript 2 O molecules. Each bond in this structure is directed toward the O atom in each H subscript 2 O structure. This structure is enclosed in brackets. Outside the brackets to the right is a superscript 2 plus sign.
The complexes (a) [Ag(NH 3 ) 2 ] + , (b) [Cu(Cl) 4 ] 2− , and (c) [Co(H 2 O) 6 ] 2+ have coordination numbers of two, four, and six, respectively. The geometries of these complexes are the same as we have seen with VSEPR theory for main group elements: linear, tetrahedral, and octahedral.

Many other ligands coordinate to the metal in more complex fashions. Bidentate ligands are those in which two atoms coordinate to the metal center. For example, ethylenediamine (en, H 2 NCH 2 CH 2 NH 2 ) contains two nitrogen atoms, each of which has a lone pair and can serve as a Lewis base ( [link] ). Both of the atoms can coordinate to a single metal center. In the complex [Co(en) 3 ] 3+ , there are three bidentate en ligands, and the coordination number of the cobalt(III) ion is six. The most common coordination numbers are two, four, and six, but examples of all coordination numbers from 1 to 15 are known.

Two structures are shown. In a, H subscript 2 N appears at the left end of the structure. A short line segment extends up and to the right from the N atom to a C atom in a C H subscript 2 group. A short line segment extends down and to the right to another C atom in a C H subscript 2 group. A final short line segment extends from this C H subscript 2 group up and to the right to the N atom of an N H subscript 2 group. Each N atom in the structure has a pair of electron dots at its top. In b, a central C o atom has six N H subscript 2 groups attached with single bonds. These bonds are indicated with line segments extending above and below, dashed wedges extending up and to the left and right, and solid wedges extending below and to the left and right. The bonds to these groups are all directed toward the N atoms. The N H subscript 2 groups are each connected to C atoms of C H subscript 2 groups extending outward from the central C o atom. These C H subscript 2 groups are connected in pairs with bonds indicated by short line segments, forming 3 rings in the structure. This entire structure is enclosed in brackets. Outside the brackets to the right is a superscript 3 plus sign.
(a) The ethylenediamine (en) ligand contains two atoms with lone pairs that can coordinate to the metal center. (b) The cobalt(III) complex [ Co ( en ) 3 ] 3+ contains three of these ligands, each forming two bonds to the cobalt ion.

Any ligand that bonds to a central metal ion by more than one donor atom is a polydentate ligand    (or “many teeth”) because it can bite into the metal center with more than one bond. The term chelate    (pronounced “KEY-late”) from the Greek for “claw” is also used to describe this type of interaction. Many polydentate ligands are chelating ligands , and a complex consisting of one or more of these ligands and a central metal is a chelate. A chelating ligand is also known as a chelating agent. A chelating ligand holds the metal ion rather like a crab’s claw would hold a marble. [link] showed one example of a chelate. The heme complex in hemoglobin is another important example ( [link] ). It contains a polydentate ligand with four donor atoms that coordinate to iron.

A structure is shown for the single ligand heme. At the center of this structure is an F e atom. From this atom, four single bonds extend up and to the right and left and below and to the right and left to four N atoms which are shown in red. Each N atom is a component of a 5 member ring with four C atoms. Each of these rings has a double bond between the C atoms that are not bonded to the N atom. The C atoms that are bonded to N atoms are connected to C atoms that serve as links between the 5-member rings. The bond to the C atom clockwise from the 5-member ring in each case is a double bond. The bond to the C atom counterclockwise from the 5-member ring in each case is a single bond. To the left of the structure, two of the C atoms in the 5-member rings that are not bonded to N are bonded to C H subscript 3 groups. The other carbons in these rings that are not bonded to N atoms are bonded to groups above and below. Above is a C H group double bonded to a C H subscript 2 group. Below is a C H subscript 2 group bonded to another C H subscript 2 group, which is bonded to a C O subscript 2 H group. At the right side of the structure, the C atoms in the 5-member rings that are not bonded to N atoms are bonded to additional structures. The C atom at to the right in the 5-member ring at the upper right is bonded to a C H group which is in turn double bonded to a C H subscript 2 group. Similarly, the right most C atom from the 5-member ring in the lower right is bonded to a C H subscript 3 group. The C atom from the 5-member ring not bonded to an N atom in the upper right region of the structure is bonded to a C H subscript 3 group above. Similarly, the C atom on the 5-member ring not bonded to an N atom in the lower right region of the structure is bonded to a C H subscript 2 group that is bonded to another C H subscript 2 group, which is bonded to a C O subscript 2 H group below.
The single ligand heme contains four nitrogen atoms that coordinate to iron in hemoglobin to form a chelate.

Polydentate ligands are sometimes identified with prefixes that indicate the number of donor atoms in the ligand. As we have seen, ligands with one donor atom, such as NH 3 , Cl , and H 2 O, are monodentate ligands. Ligands with two donor groups are bidentate ligands. Ethylenediamine, H 2 NCH 2 CH 2 NH 2 , and the anion of the acid glycine, NH 2 CH 2 CO 2 ( [link] ) are examples of bidentate ligands. Tridentate ligands, tetradentate ligands, pentadentate ligands, and hexadentate ligands contain three, four, five, and six donor atoms, respectively. The ligand in heme ( [link] ) is a tetradentate ligand.

A structure is shown. At the center of this structure is an P t atom. From this atom, two single bonds extend up and to the right and below and to the left to two O atoms which are shown in red. Similarly, two bonds extend up and to the left and down and to the right to N atoms in N H subscript 2 groups. The N atoms in these groups are in red. The N atoms are bonded to C H subscript 2 groups, which in turn are bonded to C atoms. These C atoms have doubly bonded O atoms bonded and oriented toward the outside of the structure. They are also singly bonded to the O atoms in the structure forming two rings connected by the central P t atom.
Each of the anionic ligands shown attaches in a bidentate fashion to platinum(II), with both a nitrogen and oxygen atom coordinating to the metal.

The naming of complexes

The nomenclature of the complexes is patterned after a system suggested by Alfred Werner, a Swiss chemist and Nobel laureate, whose outstanding work more than 100 years ago laid the foundation for a clearer understanding of these compounds. The following five rules are used for naming complexes:

Questions & Answers

what does the term carbon-12 scale mean
Amanda Reply
how can I encounter plasma
Blessing
what are the six types of elements
Rebecca Reply
carbon,hydrogen,nitrogen,oxygen,phosphorus and sulphur....#the CHNOPS element
Amanda
👍
clement
those are the six types of elements I know
Amanda
Yea
clement
thats all
Davy
which table is flammable
Blessing Reply
I haven't gotten to tables o 😥
Rebecca
pls how can I give an IUPAC nomenclature in organic chemistry
Moshood Reply
The Akanes, Akenes, Akynes, Alkanols, Alkanals and so on. you can further bring out the structural and empirical formula which also is a good example to represent it's numenclature.
Andrew
Paul's exclusion principle
Anuforo Reply
what do you mean by d block ,give more details element
Agburum Reply
d block elements are also called transition metals. It includes elements from group 3-12 and d block elements hold up to 10 electrons in their shell
Amanda
all?
Davy
they are called transition elements
Andrew
Define chemical formula
Kevin Reply
they are the mathematical representation of chemicals I guess
Uche
Bohr model of hydrogen atom
Muhammad Reply
what is important of this model
nagesh
this question is not correct, it is Boyles law.
Andrew
what is the main reaction between sodium and chlorine
Akeem Reply
when a sodium atom is transferred an electron to a chloride atom forming a sodium cation and a chlorde anoin both ions are compltely valence shells and a energetically more stable this reaction is extremely more exothermic producing a bright yellow light abd a great deal of heat energy
sani
well what kind of sodium
coland
sodium chloride
coland
Tyropanoic acid and its salt sodium tyropanoate are radiocontrast agents used in cholecystography (X-ray diagnosis of gallstones). Trade names include Bilopaque, Lumopaque, Tyropaque, and Bilopac. The molecule contains three heavy iodine atoms which obstruct X-rays in the same way as the calcium in
coland
Sodium tetradecyl sulfate (STS) is a commonly used synonym for 7-ethyl-2-methyl-4-undecanyl sulfate sodium salt which is anionic surfactant that is the active component of the sclerosant drug Sotradecol. It is commonly used in the treatment of varicose and spider veins of the leg, during the procedu
coland
Sodium stibogluconate, sold under the brand name Pentostam among others, is a medication used to treat leishmaniasis. This includes leishmaniasis of the cutaneous, visceral, and mucosal types. Some combination of miltefosine, paramycin and liposomal amphotericin B; however, may be recommended due to
coland
Sodium picosulfate (INN, also known as sodium picosulphate) is a Contact stimulant laxative used as a treatment for constipation or to prepare the large bowel before colonoscopy or surgery. It is sold under the trade names Sodipic Picofast, Laxoberal, Laxoberon, Purg-Odan, Picolax, Guttalax, Namilax
coland
Ipodate sodium (sodium iopodate) is an iodine-containing radiopaque contrast media used for X-rays. The drug is given orally and the resulting contrast allows for easy resolution of the bile duct and gall bladder. Other uses Although not FDA approved, ipodate sodium has been used to treat Graves'
coland
Sodium ferric gluconate complex (brand name ferrlecit by Sanofi), is an intravenously administered iron product indicated in the treatment of iron deficiency anemia. It is frequently used in patients undergoing hemodialysis, those undergoing erythropoietin therapy, and/or patients who have chronic k
coland
Dehydrocholic acid is a synthetic bile acid, manufactured by the oxidation of cholic acid. It acts as a hydrocholeretic, increasing bile output to clear increased bile acid load.
coland
Ethylenediaminetetraacetic acid (EDTA), also known by several other names, is an aminopolycarboxylic acid and a colourless, water-soluble solid. Its conjugate base is ethylenediaminetetraacetate. It is widely used to dissolve limescale. Its usefulness arises because of its role as a hexadentate ("s
coland
Sodium aurothiomalate (INN, known in the United States as gold sodium thiomalate) is a gold compound that is used for its immunosuppressive anti-rheumatic effects. Along with an orally-administered gold salt, auranofin, it is one of only two gold compounds currently employed in modern medicine. Med
coland
Sodium ascorbate is one of a number of mineral salts of ascorbic acid (vitamin C). The molecular formula of this chemical compound is C6H7NaO6. As the sodium salt of ascorbic acid, it is known as a mineral ascorbate. It has not been demonstrated to be more bioavailable than any other form of vitamin
coland
Diatrizoic acid (or its anionic form, diatrizoate), also known as amidotrizoic acid, or 3,5-diacetamido-2,4,6-triiodobenzoic acid, is a radiocontrast agent containing iodine. Trade names include Hypaque, Gastrografin, Iothalmate and Urografin, the latter being a combination of the sodium and meglum
coland
Sodium acetrizoate (rINN, trade names Urokon, Triurol and Salpix), the sodium salt of acetrizoic acid, is a high-osmolality, water-soluble, iodine-based radiographic contrast medium no longer in clinical use. Acetrizoate was developed by V.H. Wallingford of Mallinckrodt, and introduced in 1950; it
coland
i think some was missed
coland
what chlorine L-Alpha glycerylphosphorylcholine (alpha-GPC, choline alfoscerate) is a natural choline compound found in the brain. It is also a parasympathomimetic acetylcholine precursor which may have potential for the treatment of Alzheimer's disease and other dementias. Alpha-GPC rapidly delive
coland
Choline Theophyllinate , also known as oxtriphylline, is a cough medicine derived from xanthine that acts as a bronchodilator to open up airways in the lung. Chemically, it is a salt of choline and Theophylline. It classifies as an expectorant. The drug is available under the brand names Choledyl an
coland
Choline (/ˈkoʊlin/) is a water-soluble vitamin. It is usually grouped within the B-complex vitamins. The term cholines refers to the class of quaternary ammonium salts containing the N,N,N-trimethylethanolammonium cation (X− on the right denotes an undefined counteranion). The cation appears in the
coland
thanks
sani
please what is redox reaction
BABARINDE
the oxidation increases
Andrew
hydrogen reacting with water
Iyenge Reply
yes
Moha
what are you trying to prove
Uche
yes
Professor
what is matter
Godgift Reply
matter is anything that has Mass and can occupy space
Moshood
apart from those device there is there any device
Eke Reply
how many elements do we have
ARUOTURE Reply
Modern Electronic Theory
Levi Reply
a new way or an improvement in modern electrical products.
Andrew
find the volume of oxygen produced from the electrolysis of acidified water of a current of a 2A was passed through the electrolysis of acidified water for 2 hours
Ngwu Reply
14400J
Ese
wrong question, go through it. oxygen cannot be produced.
Andrew

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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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