Importance of Core Revision Points: Core Revision Points are important because if you remember them strongly, many more points related to them will come out of your memory and help you to answer question and problems. Read them many times and make sure you remember them very strongly.
See for a set of questions on this topic the post
http://iit-jee-chemistry-ps.blogspot.com/2007/10/iit-jee-chemistry-questions.html
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JEE Syllabus
Nomenclature of mononuclear coordination compounds, XII 10.1,2,3
Cis-trans and ionisation isomerisms, 10.4
Hybridization and geometries of mononuclear coordination compounds (linear, tetrahedral, square planar and octahedral).10.7
The topics are covered in detail Jauhar's XII book. The section numbers are given beside the topic.
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Core Revision Points in Sections in the chapter Jauhar Book
10.1 Coordination compounds
Coordination compounds are a special class of compounds in which the centgral 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.
for example, when acqueous ammonia is addedt o green solution of nickel chloride, NiCl2, the colour changes to purple. The ni^2+ ions almost diappear from the solution. The solution on evaporation yields purple crystals corresponding to the formula [Ni(NH-3)-6]Cl-2. such a compound is called coordinatin compound. When this compound is now dissolved in water, there is hardly any evidence of Ni^2+ ions or NH-3 molecules. It ionizes to give a new species [Ni(NH-3)-6]^2+. the species in the square brackets does not ionise further. It remains as a single entity as an ion.
This is the unique feature of coordination compounds.
10.2 Important terms in Coordination compounds
A coordination entity is composed of a central atom or atoms to which are attached
other atoms or groups of atoms, which are termed ligands. A central atom occupies a
central position within the coordination entity. The ligands attached to a central
atom define a coordination polyhedron. Each ligand is assumed to be at the vertex of
an appropriate polyhedron.
The usual polyhedra are shown in Table 3.3 and they are also listed in Table 4.4. Note that these are adequate to describe most simple coordination compounds, but that real molecules do not always fall into these simple categories. In the presentation of a coordination polyhedron graphically, the lines
defining the polyhedron edges are not indicative of bonds.
However, many ligands do not behave as donors of a single electron pair. Some
ligands donate two or more electron pairs to the same central atom from different
donor atoms. Such ligands are said to be chelating ligands, and they form chelate
rings, closed by the central atom. The phenomenon is termed chelation.
The number of electron pairs donated by a single ligand to a specific central atom
is termed the denticity. Ligands that donate one pair are monodentate, those that
donate two are didentate, those that donate three are tridentate, and so on.
Sometimes ligands with two or more potential donor sites bond to two (or more)
different central atoms rather than to one, forming a bridge between central atoms. It
may not be necessary for the ligand in such a system to be like ethane-l ,2-diamine,
with two distinct potential donor atoms. A donor atom with two or more pairs of
non-bonding electrons in its valence shell can also donate them to different centralatoms. Such ligands, of whatever type, are called bridging ligands. They bond to two
or more central atoms simultaneously. The number of central atoms in a single
coordination entity is denoted by the nuclearity: mononuclear, dinuclear, trinuclear,
etc. Atoms that can bridge include 5, 0 and Cl.
The original concepts of metal—ligand bonding were essentially related to the
dative covalent bond; the development of organometallic chemistry has revealed a
further way in which ligands can supply more than one electron pair to a central
atom. This is exemplified by the classical cases of bis(benzene)chromium and
bis(cyclopentadienyl)iron, trivial name ferrocene. These molecules are characterised
by the bonding of a formally unsaturated system (in the organic chemistry sense, but
expanded to include aromatic systems) to a central atom, usually a metal atom.
10.3 IUPAC formulation and nomenclature of Coordination compounds
10.4 Isomerism in Coordination compounds
Ionisation isomers:
Molecular structural formula is same. But different isomers give different ions in solution.
one isomer [PtBr(NH3)3]NO2 -> gives NO2- anions in solution
another isomer [Pt(NH3)3(NO2)]Br -> gives Br- anions in solution
Notice that both anions are necessary to balance the charge of the complex, and that they differ in that one ion is directly attached to the central metal but the other is not.
Geometric Isomers or Cis-Trans isomers
Geometric isomers are two or more coordination compounds which contain the same number and types of atoms, and bonds (i.e., the connectivity between atoms is the same), but which have different spatial arrangements of the atoms.
Not all coordination compounds have geometric isomers.
For example, in the square planar molecule, Pt(NH3)2Cl2, the two ammonia ligands (or the two chloride ligands) can be adjacent to one another or opposite one another.
Note that these two structures contain the same number and kinds of atoms and bonds but are non-superimposable. The isomer in which like ligands are adjacent to one another is called the cis isomer. The isomer in which like ligands are opposite one another is called the trans isomer.
For the common structures which contain two or more different ligands, geometric isomers are possible only with square planar and octahedral structures (i.e., geometric isomers cannot exist for linear and tetrahedral structures).
cis-[Co(NH3)4Cl2]+
Note that the two chloride ligands are adjacent to one another in this octahedral complex ion. In aqueous solution, this complex ion has a violet color.
trans-[Co(NH3)4Cl2]+
Note that the two chloride ligands are opposite one another in this complex ion. In aqueous solution, this complex ion has a green color.
------------------
Material about all isomers - In syllabus only ionic and cis-trans are specially mentioned
http://www.chem.purdue.edu/gchelp/cchem/whatis2.html
Coordination Isomers
Coordination isomers are two or more coordination compounds in which the composition within the coordination sphere (i.e., the metal atom plus the ligands that are bonded to it) is different (i.e., the connectivity between atoms is different).
Not all coordination compounds have coordination isomers.
Coordination isomers have different physical and chemical properties.
Example
[Cr(NH3)5(OSO3)]Br
Note that the sulfate group is bonded to the Cr atom (via an O atom) and is within the coordination sphere. Note also the octahedral structure. The bromide counterion is needed to maintain charge neutrality with the complex ion (i.e., [Cr(NH3)5(OSO3)]+) and is not shown in the structure.
[Cr(NH3)5Br]SO4
Note that the bromine atom is bonded to the Cr atom and is within the coordination sphere. Note also the octahedral structure. The sulfate counterion is not shown in the structure.
Linkage Isomers
Linkage isomers are two or more coordination compounds in which the donor atom of at least one of the ligands is different (i.e., the connectivity between atoms is different).
This type of isomerism can only exist when the compound contains a ligand that can bond to the metal atom in two (or more) different ways. Some ligands that can form linkage isomers are shown below.
Not all coordination compounds have linkage isomers.
Linkage isomers have different physical and chemical properties.
[Co(NH3)4(NO2)Cl]+
Note that the N atom of the nitrite group is bonded to the Co atom. The nitrite group is written as "NO2" in the molecular formula (rather than "ONO") with the N atom nearest to the Co symbol to indicate that the N atom (rather than an O atom) is the donor atom. Note also the octahedral structure.
[Co(NH3)4(ONO)Cl]+
Note that one of the O atoms of the nitrite group is bonded to the Co atom. The nitrite group is written as "ONO" in the molecular formula (rather than "NO2") with the O atom nearest to the Co symbol to indicate that the O atom is the donor atom. Note also the octahedral structure.
Geometric Isomers
Geometric isomers are two or more coordination compounds which contain the same number and types of atoms, and bonds (i.e., the connectivity between atoms is the same), but which have different spatial arrangements of the atoms.
Not all coordination compounds have geometric isomers.
For example, in the square planar molecule, Pt(NH3)2Cl2, the two ammonia ligands (or the two chloride ligands) can be adjacent to one another or opposite one another.
Note that these two structures contain the same number and kinds of atoms and bonds but are non-superimposable. The isomer in which like ligands are adjacent to one another is called the cis isomer. The isomer in which like ligands are opposite one another is called the trans isomer.
For the common structures which contain two or more different ligands, geometric isomers are possible only with square planar and octahedral structures (i.e., geometric isomers cannot exist for linear and tetrahedral structures).
cis-[Co(NH3)4Cl2]+
Note that the two chloride ligands are adjacent to one another in this octahedral complex ion. In aqueous solution, this complex ion has a violet color.
trans-[Co(NH3)4Cl2]+
Note that the two chloride ligands are opposite one another in this complex ion. In aqueous solution, this complex ion has a green color.
Optical Isomers
Optical isomers are two compounds which contain the same number and kinds of atoms, and bonds (i.e., the connectivity between atoms is the same), and different spatial arrangements of the atoms, but which have non-superimposable mirror images. Each non-superimposable mirror image structure is called an enantiomer. Molecules or ions that exist as optical isomers are called chiral.
Not all coordination compounds have optical isomers.
The Two Enantiomers of CHBrClF
Note that the molecule on the right is the reflection of the molecule on the left (through the mirror plane indicated by the black vertical line). These two structures are non-superimposable and are, therefore, different compounds.
Pure samples of enantiomers have identical physical properties (e.g., boiling point, density, freezing point). Chiral molecules and ions have different chemical properties only when they are in chiral environments.
Optical isomers get their name because the plane of plane-polarized light that is passed through a sample of a pure enantiomer is rotated. The plane is rotated in the opposite direction but with the same magnitude when plane-polarized light is passed through a pure sample containing the other enantiomer of a pair.
10.5 Bonding in Coordination compounds
10.6 Werner’s coordination theory
Werner theory explained the bonding in coordination complexes by postulating primary valency (oxidation state) and secondary valency (coordination number).
The number of ligands attached to the central metal atom or ion is called coordination number.
10.7 Valency bond theory for bonding in Coordination compounds
10.8 Crystal theory
10.9 Stability of Coordination compounds in solution
10.10 General methods of preparation of Coordination compounds
10.11 Applications of Coordination compounds
1. Estimation of hardness of water
2. In qualitative analysis
3. In electroplating
4. In water treatment
5. In dyeing
6. Biological importance
7. In metallurgical processes
8. In medicines
9. In catalysis
10.12 Organometallic compounds
10.13 Bonding in organometallic compounds
10.14 Synthesis of organometallic compounds
Sections in the chapter Jauhar Book
10.1 Coordination compounds
10.2 Important terms in Coordination compounds
Practice Problems: 10.1 to 10.5
10.3 IUPAC formulation and nomenclature of Coordination compounds
P.P. 10.6
10.4 Isomerism in Coordination compounds
P.P. 107 to 10.10
10.5 Bonding in Coordination compounds
10.6 Werner’s coordination theory
10.7 Valency bond theory for bonding in Coordination compounds
10.8 Crystal theory
10.9 Stability of Coordination compounds in solution
10.10 General methods of preparation of Coordination compounds
10.11 Applications of Coordination compounds
10.12 Organometallic compounds
10.13 Bonding in organometallic compounds
10.14 Synthesis of organometallic compounds
__________________
__________________
See for a set of questions on this topic the post
http://iit-jee-chemistry-ps.blogspot.com/2007/10/iit-jee-chemistry-questions.html
----------------------
JEE Syllabus
Nomenclature of mononuclear coordination compounds, XII 10.1,2,3
Cis-trans and ionisation isomerisms, 10.4
Hybridization and geometries of mononuclear coordination compounds (linear, tetrahedral, square planar and octahedral).10.7
The topics are covered in detail Jauhar's XII book. The section numbers are given beside the topic.
-----------------------
Core Revision Points in Sections in the chapter Jauhar Book
10.1 Coordination compounds
Coordination compounds are a special class of compounds in which the centgral 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.
for example, when acqueous ammonia is addedt o green solution of nickel chloride, NiCl2, the colour changes to purple. The ni^2+ ions almost diappear from the solution. The solution on evaporation yields purple crystals corresponding to the formula [Ni(NH-3)-6]Cl-2. such a compound is called coordinatin compound. When this compound is now dissolved in water, there is hardly any evidence of Ni^2+ ions or NH-3 molecules. It ionizes to give a new species [Ni(NH-3)-6]^2+. the species in the square brackets does not ionise further. It remains as a single entity as an ion.
This is the unique feature of coordination compounds.
10.2 Important terms in Coordination compounds
A coordination entity is composed of a central atom or atoms to which are attached
other atoms or groups of atoms, which are termed ligands. A central atom occupies a
central position within the coordination entity. The ligands attached to a central
atom define a coordination polyhedron. Each ligand is assumed to be at the vertex of
an appropriate polyhedron.
The usual polyhedra are shown in Table 3.3 and they are also listed in Table 4.4. Note that these are adequate to describe most simple coordination compounds, but that real molecules do not always fall into these simple categories. In the presentation of a coordination polyhedron graphically, the lines
defining the polyhedron edges are not indicative of bonds.
However, many ligands do not behave as donors of a single electron pair. Some
ligands donate two or more electron pairs to the same central atom from different
donor atoms. Such ligands are said to be chelating ligands, and they form chelate
rings, closed by the central atom. The phenomenon is termed chelation.
The number of electron pairs donated by a single ligand to a specific central atom
is termed the denticity. Ligands that donate one pair are monodentate, those that
donate two are didentate, those that donate three are tridentate, and so on.
Sometimes ligands with two or more potential donor sites bond to two (or more)
different central atoms rather than to one, forming a bridge between central atoms. It
may not be necessary for the ligand in such a system to be like ethane-l ,2-diamine,
with two distinct potential donor atoms. A donor atom with two or more pairs of
non-bonding electrons in its valence shell can also donate them to different centralatoms. Such ligands, of whatever type, are called bridging ligands. They bond to two
or more central atoms simultaneously. The number of central atoms in a single
coordination entity is denoted by the nuclearity: mononuclear, dinuclear, trinuclear,
etc. Atoms that can bridge include 5, 0 and Cl.
The original concepts of metal—ligand bonding were essentially related to the
dative covalent bond; the development of organometallic chemistry has revealed a
further way in which ligands can supply more than one electron pair to a central
atom. This is exemplified by the classical cases of bis(benzene)chromium and
bis(cyclopentadienyl)iron, trivial name ferrocene. These molecules are characterised
by the bonding of a formally unsaturated system (in the organic chemistry sense, but
expanded to include aromatic systems) to a central atom, usually a metal atom.
10.3 IUPAC formulation and nomenclature of Coordination compounds
10.4 Isomerism in Coordination compounds
Ionisation isomers:
Molecular structural formula is same. But different isomers give different ions in solution.
one isomer [PtBr(NH3)3]NO2 -> gives NO2- anions in solution
another isomer [Pt(NH3)3(NO2)]Br -> gives Br- anions in solution
Notice that both anions are necessary to balance the charge of the complex, and that they differ in that one ion is directly attached to the central metal but the other is not.
Geometric Isomers or Cis-Trans isomers
Geometric isomers are two or more coordination compounds which contain the same number and types of atoms, and bonds (i.e., the connectivity between atoms is the same), but which have different spatial arrangements of the atoms.
Not all coordination compounds have geometric isomers.
For example, in the square planar molecule, Pt(NH3)2Cl2, the two ammonia ligands (or the two chloride ligands) can be adjacent to one another or opposite one another.
Note that these two structures contain the same number and kinds of atoms and bonds but are non-superimposable. The isomer in which like ligands are adjacent to one another is called the cis isomer. The isomer in which like ligands are opposite one another is called the trans isomer.
For the common structures which contain two or more different ligands, geometric isomers are possible only with square planar and octahedral structures (i.e., geometric isomers cannot exist for linear and tetrahedral structures).
cis-[Co(NH3)4Cl2]+
Note that the two chloride ligands are adjacent to one another in this octahedral complex ion. In aqueous solution, this complex ion has a violet color.
trans-[Co(NH3)4Cl2]+
Note that the two chloride ligands are opposite one another in this complex ion. In aqueous solution, this complex ion has a green color.
------------------
Material about all isomers - In syllabus only ionic and cis-trans are specially mentioned
http://www.chem.purdue.edu/gchelp/cchem/whatis2.html
Coordination Isomers
Coordination isomers are two or more coordination compounds in which the composition within the coordination sphere (i.e., the metal atom plus the ligands that are bonded to it) is different (i.e., the connectivity between atoms is different).
Not all coordination compounds have coordination isomers.
Coordination isomers have different physical and chemical properties.
Example
[Cr(NH3)5(OSO3)]Br
Note that the sulfate group is bonded to the Cr atom (via an O atom) and is within the coordination sphere. Note also the octahedral structure. The bromide counterion is needed to maintain charge neutrality with the complex ion (i.e., [Cr(NH3)5(OSO3)]+) and is not shown in the structure.
[Cr(NH3)5Br]SO4
Note that the bromine atom is bonded to the Cr atom and is within the coordination sphere. Note also the octahedral structure. The sulfate counterion is not shown in the structure.
Linkage Isomers
Linkage isomers are two or more coordination compounds in which the donor atom of at least one of the ligands is different (i.e., the connectivity between atoms is different).
This type of isomerism can only exist when the compound contains a ligand that can bond to the metal atom in two (or more) different ways. Some ligands that can form linkage isomers are shown below.
Not all coordination compounds have linkage isomers.
Linkage isomers have different physical and chemical properties.
[Co(NH3)4(NO2)Cl]+
Note that the N atom of the nitrite group is bonded to the Co atom. The nitrite group is written as "NO2" in the molecular formula (rather than "ONO") with the N atom nearest to the Co symbol to indicate that the N atom (rather than an O atom) is the donor atom. Note also the octahedral structure.
[Co(NH3)4(ONO)Cl]+
Note that one of the O atoms of the nitrite group is bonded to the Co atom. The nitrite group is written as "ONO" in the molecular formula (rather than "NO2") with the O atom nearest to the Co symbol to indicate that the O atom is the donor atom. Note also the octahedral structure.
Geometric Isomers
Geometric isomers are two or more coordination compounds which contain the same number and types of atoms, and bonds (i.e., the connectivity between atoms is the same), but which have different spatial arrangements of the atoms.
Not all coordination compounds have geometric isomers.
For example, in the square planar molecule, Pt(NH3)2Cl2, the two ammonia ligands (or the two chloride ligands) can be adjacent to one another or opposite one another.
Note that these two structures contain the same number and kinds of atoms and bonds but are non-superimposable. The isomer in which like ligands are adjacent to one another is called the cis isomer. The isomer in which like ligands are opposite one another is called the trans isomer.
For the common structures which contain two or more different ligands, geometric isomers are possible only with square planar and octahedral structures (i.e., geometric isomers cannot exist for linear and tetrahedral structures).
cis-[Co(NH3)4Cl2]+
Note that the two chloride ligands are adjacent to one another in this octahedral complex ion. In aqueous solution, this complex ion has a violet color.
trans-[Co(NH3)4Cl2]+
Note that the two chloride ligands are opposite one another in this complex ion. In aqueous solution, this complex ion has a green color.
Optical Isomers
Optical isomers are two compounds which contain the same number and kinds of atoms, and bonds (i.e., the connectivity between atoms is the same), and different spatial arrangements of the atoms, but which have non-superimposable mirror images. Each non-superimposable mirror image structure is called an enantiomer. Molecules or ions that exist as optical isomers are called chiral.
Not all coordination compounds have optical isomers.
The Two Enantiomers of CHBrClF
Note that the molecule on the right is the reflection of the molecule on the left (through the mirror plane indicated by the black vertical line). These two structures are non-superimposable and are, therefore, different compounds.
Pure samples of enantiomers have identical physical properties (e.g., boiling point, density, freezing point). Chiral molecules and ions have different chemical properties only when they are in chiral environments.
Optical isomers get their name because the plane of plane-polarized light that is passed through a sample of a pure enantiomer is rotated. The plane is rotated in the opposite direction but with the same magnitude when plane-polarized light is passed through a pure sample containing the other enantiomer of a pair.
10.5 Bonding in Coordination compounds
10.6 Werner’s coordination theory
Werner theory explained the bonding in coordination complexes by postulating primary valency (oxidation state) and secondary valency (coordination number).
The number of ligands attached to the central metal atom or ion is called coordination number.
10.7 Valency bond theory for bonding in Coordination compounds
10.8 Crystal theory
10.9 Stability of Coordination compounds in solution
10.10 General methods of preparation of Coordination compounds
10.11 Applications of Coordination compounds
1. Estimation of hardness of water
2. In qualitative analysis
3. In electroplating
4. In water treatment
5. In dyeing
6. Biological importance
7. In metallurgical processes
8. In medicines
9. In catalysis
10.12 Organometallic compounds
10.13 Bonding in organometallic compounds
10.14 Synthesis of organometallic compounds
Sections in the chapter Jauhar Book
10.1 Coordination compounds
10.2 Important terms in Coordination compounds
Practice Problems: 10.1 to 10.5
10.3 IUPAC formulation and nomenclature of Coordination compounds
P.P. 10.6
10.4 Isomerism in Coordination compounds
P.P. 107 to 10.10
10.5 Bonding in Coordination compounds
10.6 Werner’s coordination theory
10.7 Valency bond theory for bonding in Coordination compounds
10.8 Crystal theory
10.9 Stability of Coordination compounds in solution
10.10 General methods of preparation of Coordination compounds
10.11 Applications of Coordination compounds
10.12 Organometallic compounds
10.13 Bonding in organometallic compounds
10.14 Synthesis of organometallic compounds
__________________
__________________
Rao IIT Academy
01/22 M Learning
__________________
__________________
mlearning India
Updated 6 January 2020, 31 Jan 2016, 23 May 2015
01/22 M Learning
__________________
__________________
mlearning India
Updated 6 January 2020, 31 Jan 2016, 23 May 2015
