IUPAC Nomenclature: Organic Chemistry Basics for IIT JEE, Online AIPMT, ...

Isomerism

Isomerism

Coordination compounds often exist as isomers—i.e., as compounds with the same chemical composition but different structural formulas. Many different kinds of isomerism occur among coordination compounds. The following are some of the more common types.

Cis-trans isomerism

Cis-trans (geometric) isomers of coordination compounds differ from one another only in the manner in which the ligands are distributed spatially; for example, in the isomeric pair of diamminedichloroplatinum compounds
the two ammonia molecules and the two chlorine atoms are situated next to one another in one isomer, called the cis (Latin for “on this side”) isomer, and across from one another in the other, the trans (Latin for “on the other side”) isomer. A similar relationship exists between the cis and trans forms of the tetraamminedichlorocobalt(1+) ion:
 

Enantiomers and diastereomers

So-called optical isomers (or enantiomers) have the ability to rotate plane-polarized light in opposite directions. Enantiomers exist when the molecules of the substances are mirror images but are not superimposable upon one another. In coordination compounds, enantiomers can arise either from the presence of an asymmetric ligand, such as one isomer of the amino acid, alanine (aminopropionic acid),
or from an asymmetric arrangement of the ligands. Familiar examples of the latter variety are octahedral comp

lexes carrying three didentate ligands, such as ethylenediamine, NH₂CH₂CH₂NH₂. The two enantiomers corresponding to such a complex are depicted by the structures below.

The ethylenediamine ligands above are indicated by a curved line between the symbols for the nitrogen atoms.
Diastereomers, on the other hand, are not superimposable and also are not mirror images. Using AB as an example of a chelating ligand, in which the symbol AB implies that the two ends of the chelate are different, there are six possible isomers of a complex cis-[M(AB)₂X₂]. For example, AB might correspond to alanine [CH₃CH(NH₂)C(O)O]⁻, where both N and O are attached to the metal. Alternatively, AB could represent a ligand such as propylenenediamine, [NH₂CH₂C(CH₃)HNH₂], where the two ends of the molecule are distinguished by the fact that one of the Hs on a C is substituted with a methyl (CH₃) group.

Ionization isomerism

Certain isomeric pairs occur that differ only in that two ionic groups exchange positions within (and without) the primary coordination sphere. These are called ionization isomers and are exemplified by the two compounds, pentaamminebromocobalt sulfate, [CoBr(NH₃)₅]SO₄, and pentaamminesulfatocobalt bromide, [Co(SO₄)(NH₃)₅]Br. In the former the bromide ion is coordinated to the cobalt(3+) ion, and the sulfate ion is outside the coordination sphere; in the latter the sulfate ion occurs within the coordination sphere, and the bromide ion is outside it.

Linkage isomerism

Isomerism also results when a given ligand is joined to the central atom through different atoms of the ligand. Such isomerism is called linkage isomerism. A pair of linkage isomers are the ions [Co(NO₂)(NH₃)₅]²⁺and [Co(ONO)(NH₃)₅]²⁺, in which the anionic ligand is joined to the cobalt atom through nitrogen or oxygen, as shown by designating it with the formulas NO₂⁻(nitro) and ONO⁻(nitrito), respectively. Another example of this variety of isomerism is given by the pair of ions [Co(CN)₅(NCS)]³⁻ and [Co(CN)₅(SCN)]³⁻, in which an isothiocyanate (NCS)⁻ and a thiocyanate group (SCN)⁻ are bonded to the cobalt(3+) ion through a nitrogen or sulfur atom, respectively.

Coordination isomerism

Ionic coordination compounds that contain complex cations and anions can exist as isomers if the ligands associated with the two metal atoms are exchanged, as in the pair of compounds, hexaamminecobalt(3+) hexacyanochromate(3–), [Co(NH₃)₆][Cr(CN)₆], and hexaamminechromium(3+) hexacyanocobaltate(3–), [Cr(NH₃)₆][Co(CN)₆]. Such compounds are called coordination isomers, as are the isomeric pairs obtained by redistributing the ligands between the two metal atoms, as in the doubly coordinated pair, tetraammineplatinum(2+) hexachloroplatinate(2–), [Pt(NH₃)₄][PtCl₆], and tetraamminedichloroplatinum(2+) tetrachloroplatinate(2–), [PtCl₂(NH₃)₄][PtCl₄].

Ligand isomerism

Isomeric coordination compounds are known in which the overall isomerism results from isomerism solely within the ligand groups. An example of such isomerism is shown by the ions, bis(1,3-diaminopropane)platinum(2+) and bis(1,2-diaminopropane)platinum(2+),

Coordination numbers and geometries

 hexacyanoferrate(III) ion, [Fe(CN)₆]³⁻




Coordination numbers and geometries of metal cyanide complexes

electron configuration*	metal ion	cyanide complex	geometry	total number of valence electrons
d2	Mo4+	[Mo(CN)8]4−	dodecahedral	18
d3	Cr3+	[Cr(CN)6]3−	octahedral	15
d4	Mn3+	[Mn(CN)6]3−	octahedral	16
d5	Fe3+	[Fe(CN)6]3−	octahedral	17
d6	Co3+	[Co(CN)6]3−	octahedral	18
d7	Co2+	[Co(CN)5]3−	square pyramidal	17
d8	Ni2+	[Ni(CN)4]2−	square planar	16
d8	Ni2+	[Ni(CN)5]3−	square pyramidal or trigonal bipyramidal	18
d10	Cd2+	[Cd(CN)4]2−	tetrahedral	18
d10	Ag+	[Ag(CN)2]−	linear	14

Coordination compounds in nature

Coordination compounds in nature
Naturally occurring coordination compounds are vital to living organisms. Metal complexes play a variety of important roles in biological systems. Many enzymes, the naturally occurring catalysts that regulate biological processes, are metal complexes (metalloenzymes); for example, carboxypeptidase, a hydrolytic enzyme important in digestion, contains a zinc ion coordinated to several amino acid residues of the protein. Another enzyme, catalase, which is an efficient catalyst for the decomposition of hydrogen peroxide, contains iron-porphyrin complexes. In both cases, the coordinated metal ions are probably the sites of catalytic activity. Hemoglobin also contains iron-porphyrin complexes, its role as an oxygen carrier being related to the ability of the iron atoms to coordinate oxygen molecules reversibly. Other biologically important coordination compounds include chlorophyll (a magnesium-porphyrin complex) and vitamin B₁₂, a complex of cobalt with a macrocyclic ligand known as corrin.

Naming Coordination Compounds and practice

Naming Coordination Compounds

A complex is a substance in which a metal atom or ion is associated with a group of neutral molecules or anions called ligands. Coordination compounds are neutral substances (i.e. uncharged) in which at least one ion is present as a complex. You will learn more about coordination compounds in the lab lectures of experiment 4 in this course.

The coordination compounds are named in the following way. (At the end of this tutorial we have some examples to show you how coordination compounds are named.)

A. To name a coordination compound, no matter whether the complex ion is the cation or the anion, always name the cation before the anion. (This is just like naming an ionic compound.)

B. In naming the complex ion:

1. Name the ligands first, in alphabetical order, then the metal atom or ion. Note: The metal atom or ion is written before the ligands in the chemical formula.
2. The names of some common ligands are listed in Table 1.
� For anionic ligands end in "-o"; for anions that end in "-ide"(e.g. chloride), "-ate" (e.g. sulfate, nitrate), and "-ite" (e.g. nirite), change the endings as follows: -ide -o; -ate -ato; -ite -ito
� For neutral ligands, the common name of the molecule is used e.g. H₂NCH₂CH₂NH₂ (ethylenediamine). Important exceptions: water is called ‘aqua’, ammonia is called ‘ammine’, carbon monoxide is called ‘carbonyl’, and the N₂ and O₂ are called ‘dinitrogen’ and ‘dioxygen’.

Table 1. Names of Some Common Ligands

Anionic Ligands	Names		Neutral Ligands	Names
Br-	bromo		NH3	ammine
F-	fluoro		H2O	aqua
O2-	oxo		NO	Nitrosyl
OH-	Hydroxo		CO	Carbonyl
CN-	cyano		O2	dioxygen
C2O42-	oxalato		N2	dinitrogen
CO32-	carbonato		C5H5N	pyridine
CH3COO-	acetato		H2NCH2CH2NH2	ethylenediamine

3. Greek prefixes are used to designate the number of each type of ligand in the complex ion, e.g. di-, tri- and tetra-. If the ligand already contains a Greek prefix (e.g. ethylenediamine) or if it is polydentate ligands (ie. can attach at more than one binding site) the prefixes bis-, tris-, tetrakis-, pentakis-, are used instead. (See examples 3 and 4.) The numerical prefixes are listed in Table 2.

Table 2. Numerical Prefixes

Number	Prefix	Number	Prefix	Number	Prefix
1	mono	5	penta (pentakis)	9	nona (ennea)
2	di (bis)	6	hexa (hexakis)	10	deca
3	tri (tris)	7	hepta	11	undeca
4	tetra (tetrakis)	8	octa	12	dodeca

4. After naming the ligands, name the central metal. If the complex ion is a cation, the metal is named same as the element. For example, Co in a complex cation is call cobalt and Pt is called platinum. (See examples 1-4). If the complex ion is an anion, the name of the metal ends with the suffix –ate. (See examples 5 and 6.). For example, Co in a complex anion is called cobaltate and Pt is called platinate. For some metals, the Latin names are used in the complex anions e.g. Fe is called ferrate (not ironate).

Table 3: Name of Metals in Anionic Complexes

Name of Metal	Name in an Anionic Complex
Iron	Ferrate
Copper	Cuprate
Lead	Plumbate
Silver	Argenate
Gold	Aurate
Tin	Stannate

5. Following the name of the metal, the oxidation state of the metal in the complex is given as a Roman numeral in parentheses.

C. To name a neutral complex molecule, follow the rules of naming a complex cation. Remember: Name the (possibly complex) cation BEFORE the (possibly complex) anion.See examples 7 and 8.
For historic reasons, some coordination compounds are called by their common names. For example, Fe(CN)₆^3- and Fe(CN)₆^4- are named ferricyanide and ferrocyanide respectively, and Fe(CO)₅ is called iron carbonyl.

Examples Give the systematic names for the following coordination compounds:

1. [Cr(NH₃)₃(H₂O)₃]Cl₃

Answer: triamminetriaquachromium(III) chloride
Solution: The complex ion is inside the parentheses, which is a cation.
The ammine ligands are named before the aqua ligands according to alphabetical order.
Since there are three chlorides binding with the complex ion, the charge on the complex ion must be +3 ( since the compound is electrically neutral).
From the charge on the complex ion and the charge on the ligands, we can calculate the oxidation number of the metal. In this example, all the ligands are neutral molecules. Therefore, the oxidation number of chromium must be same as the charge of the complex ion, +3.

2. [Pt(NH₃)₅Cl]Br₃

Answer: pentaamminechloroplatinum(IV) bromide
Solution: The complex ion is a cation, the counter anion is the 3 bromides.
The charge of the complex ion must be +3 since it bonds with 3 bromides.
The NH₃ are neutral molecules while the chloride carries - 1 charge. Therefore, the oxidation number of platinum must be +4.

3. [Pt(H₂NCH₂CH₂NH₂)₂Cl₂]Cl₂

Answer: dichlorobis(ethylenediamine)platinum(IV) chloride
Solution: ethylenediamine is a bidentate ligand, the bis- prefix is used instead of di-

4. [Co(H₂NCH₂CH₂NH₂)₃]₂(SO₄)₃

Answer: tris(ethylenediamine)cobalt(III) sulfate
Solution: The sulfate is the counter anion in this molecule. Since it takes 3 sulfates to bond with two complex cations, the charge on each complex cation must be +3.
Since ethylenediamine is a neutral molecule, the oxidation number of cobalt in the complex ion must be +3.
Again, remember that you never have to indicate the number of cations and anions in the name of an ionic compound.

5. K₄[Fe(CN)₆]

Answer: potassium hexacyanoferrate(II)
Solution: potassium is the cation and the complex ion is the anion.
Since there are 4 K⁺ binding with a complex ion, the charge on the complex ion must be - 4.
Since each ligand carries –1 charge, the oxidation number of Fe must be +2.
The common name of this compound is potassium ferrocyanide.

6. Na₂[NiCl₄]

Answer: sodium tetrachloronickelate(II)
Solution: The complex ion is the anion so we have to add the suffix –ate in the name of the metal.

7. Pt(NH₃)₂Cl₄

Answer: diamminetetrachloroplatinum(IV)
Solution: This is a neutral molecule because the charge on Pt⁺⁴ equals the negative charges on the four chloro ligands.
If the compound is [Pt(NH₃)₂Cl₂]Cl₂, eventhough the number of ions and atoms in the molecule are identical to the example, it should be named: diamminedichloroplatinum(II) chloride, a big difference.

8. Fe(CO)₅

Answer: pentacarbonyliron(0)
Solution: Since it is a neutral complex, it is named in the same way as a complex cation. The common name of this compound, iron carbonyl, is used more often.

9. (NH₄)₂[Ni(C₂O₄)₂(H₂O)₂]

Answer: ammonium diaquabis(oxalato)nickelate(II)
Solution: The oxalate ion is a bidentate ligand.

10. [Ag(NH₃)₂][Ag(CN)₂]

Answer: diamminesilver(I) dicyanoargentate(I)
You can have a compound where both the cation and the anion are complex ions. Notice how the name of the metal differs even though they are the same metal ions.

Can you give the molecular formulas of the following coordination compounds?

1. hexaammineiron(III) nitrate
2. ammonium tetrachlorocuprate(II)
3. sodium monochloropentacyanoferrate(III)
4. potassium hexafluorocobaltate(III)

Can you give the name of the following coordination compounds?

5. [CoBr(NH₃)₅]SO₄
6. [Fe(NH₃)₆][Cr(CN)₆]
7. [Co(SO₄)(NH₃)₅]⁺
8. [Fe(OH)(H₂O)₅]²⁺

Answers:

1. [Fe(NH₃)₆](NO₃)₃
2. (NH₄)₂[CuCl₄]
3. Na₃[FeCl₁(CN)₅]
4. K₃[CoF₆]
5. pentaamminebromocobalt(III) sulfate
6. hexaammineiron(III) hexacyanochromate (III)
7. pentaamminesulfatocobalt(III) ion
8. pentaaquahydroxoiron(III) ion

Blood Chemistry

Prof.piyush

Basic Blood Chemistry Tests Doctors order basic blood chemistry tests to assess a wide range of conditions and the function of organs. Often, blood tests check electrolytes, the minerals that help keep the body's fluid levels in balance, and are necessary to help the muscles, heart, and other organs work properly. To assess kidney function and blood sugar, blood tests measure other substances. Tests for Electrolytes Typically, tests for electrolytes measure levels of sodium, potassium, chloride, and bicarbonate in the body. Sodium plays a major role in regulating the amount of water in the body. Also, the passage of sodium in and out of cells is necessary for many body functions, like transmitting electrical signals in the brain and in the muscles. The sodium levels are measured to detect whether there's the right balance of sodium and liquid in the blood to carry out those functions. If a child becomes dehydrated because of vomiting, diarrhea, or inadequate fluid intake, the sodium levels can be abnormally high or low, which can cause a child to feel confused, weak, and lethargic, and even to have seizures. Potassium is essential to regulate how the heart beats. Potassium levels that are too high or too low can increase the risk of an abnormal heartbeat (also called arrhythmias). Low potassium levels are also associated with muscle weakness and cramps. Chloride, like sodium, helps maintain a balance of fluids in the body. If there's a large loss of chloride, the blood may become more acidic and prevent certain chemical reactions from occurring in the body that are necessary it to keep working properly. Bicarbonate prevents the body's tissues from getting too much or too little acid. The kidney and lungs balance the levels of bicarbonate in the body. So if bicarbonate levels are too high or low, it might indicate a problem with those organs. Other Substances Measured Other blood substances measured in the basic blood chemistry test include blood urea nitrogen and creatinine, which tell how well the kidneys are functioning, and glucose, which indicates whether there is a normal amount of sugar in the blood. Blood urea nitrogen (BUN) is a measure of how well the kidneys are working. Urea is a nitrogen-containing waste product that's created when the body breaks down protein. If the kidneys are not working properly, the levels of BUN will build up in the blood. Dehydration, excessive bleeding, and severe infection leading to shock can also elevate the BUN levels in the blood. Creatinine levels in the blood that are too high can indicate that the kidneys aren't working properly. The kidneys filter and excrete creatinine; if they're not functioning properly, creatinine can build up in the bloodstream. Both dehydration and muscle damage also can raise creatinine levels. Glucose is the main type of sugar in the blood. It comes from the foods we eat and is the major source of energy needed to fuel the body's functions. Glucose levels that are too high or too low can cause problems. The most common cause of high blood glucose levels is diabetes. Other medical conditions and some medications can also cause high blood glucose.

coordination compounds

How are coordination compounds named?

Structures of coordination compounds can be very complicated, and their names long because the ligands may already have long names. Knowing the rules of nomenclature not only enable you to understand what the complex is, but also let you give appropriate names to them. Often, several groups of the ligand are involved in a complex. The number of ligand molecules per complex is indicated by a Greek prefix: mono-, di- (or bis), tri-, tetra-, penta-, hexa, hepta-, octa-, nona-, (ennea-), deca- etc for 1, 2, 3, ... 10 etc. If the names of ligands already have one of these prefixes, the names are placed in parentheses. The prefices for the number of ligands become bis-, tris-, tetrakis, pentakis- etc.
For neutral ligands, their names are not changed, except the following few:
H₂O, aqua
NH₃, ammine (not two m's, amine is for organic compounds)
CO, carbonyl
NO, nitrosyl
Normal names that will not change
C₅H₅N, pyradine
NH₂CH₂CH₂NH₂, ethylenediamine
C₅H₄N-C₅H₄N, dipyridyl
P(C₆H₅)₃, triphenylphosphine
NH₂CH₂CH₂NHCH₂CH₂NH₂, diethylenetriamine
The last "e" in names of negative ions are changed to "o" in names of complexes. Sometimes "ide" is changed to "o". Note the following: Cl^-, chloride -> chloro
OH^-, hydroxide -> hydroxo
O^2-, oxide -> oxo
O₂^- peroxide, -> peroxo
CN^-, cyanide -> cyano

N₃^-, azide -> axido
N^3-, nitride -> nitrido
NH₂^-, amide -> amido
CO₃^2-, carbonate -> carbonato
-ONO₂^-, nitrate -> nitrato (when bonded through O)
-NO₃^-, nitrate -> nitro

coordination compound

Coordination compounds are a special class of compounds in which the central metal atom is surrounded by ions or molecules beyond their valency.

There are also referred to as coordination complexes or complexes.

Haemoglobin, Chlrophyll, and vitamin B-12 are coordinatio compounds of iron, magnesium and cobalt respectively.

The interesting thing of coordination compound is that these are formed from apparently saturated molecules capable of independent existence.