Classification of coordination compounds, Chemistry

Assignment Help:

Classification of Coordination Compounds

Since the number of known complexes is so large, we need to classify and categorise them  in order to study their chemistry systematically.

The first and the most obvious choice is to classify them on the basis of the central metal, ion. There are over eighty elements which can act as acceptor atoms in a complex. Most of: these elements like transition metals can exist in several different oxidation states. Each of these states behaves as a different kind of acceptor and forms complexes having different formulas and properties. Hence, such a classification cannot be very useful. 

A second way of classification is based on the coordination number of the metal ion. It is useful to the extent that the coordination number determines the geometry of the complex which can be correlated with properties like isomerism. However, majority of the complexes formed are either four coordinated or six-coordinated. Four-coordinated complexes commonly show square planner and less frequently tetrahedral geometry. On the other hand all six coordinated complexes invariable exist in octahedral geometry. Thus, a further sub-classification would become necessary.

 

There is yet another use fill way for the classification and that is on the basis of ligands. Ligands of one kind generally tend to give complexes with similar structure and properties. Most of the ligands are either simple anion like CI-. Br-,Nm etc. or are neutral molecules containing at least one donor atom. Let us look at the most commonly countered elements who 'se atoms, either in simple ionic form or as a part of a molecule, can act as a ligand.  These are:

                                           N                          O                                  F

                                          P                            S                                   Cl

                                          As                          Se                                 Br

                                                                                                               L

Halogens are always attached to the metal ion in a simple anionic form whereas all others commonly form a part of a molecule or ion. Examples are: NH3 H20, SCN, CH3COCH2COCH3 etc.

It is an observed fact that some metals form their most stable complexes with ligands having

N,0 and F as donor atoms. These have been grouped together and are called class 'a' elements or 'hard acids'. These include elements of Groups 1.2 and 13 or transition elements with one, two or three d-electrons. Some metals form their most stable complexes with ligands where the coordinating atom is any element (P, S, CI etc.) other than N, 0, F in the above group. These metals are referred to as class 'b' elements or 'soft acids'. These include a few transition elements such as Pt, Pd, Hg etc. A large number of elements, however, cannot be clearly classified under either of the above two categories. These include elements from Mn to Cu amongst the first transition series, and Mo, 0s. Cd etc.  These differences in behaviour of the metal ions arise due to many factors such as charg size, electronegativity, etc.


Related Discussions:- Classification of coordination compounds

Energy of an electron in the first bohr orbit of h atom, The energy of an e...

The energy of an electron in the first Bohr orbit of H atom is-13.6eV  . The possible energy value(s) of the excited state(s) for electrons in Bohr orbits to hydrogen is(are):

Explain combined gas law, Q. Explain Combined Gas Law? Ans. The  ...

Q. Explain Combined Gas Law? Ans. The  combined gas law  combines Boyle's law and Charles' law. The combined gas law describes situations where a gas undergoes simul

Define atomic mass units, Q. Define atomic mass units? Atomic mass Scie...

Q. Define atomic mass units? Atomic mass Scientists have set up a standard for the measurement of atomic mass by assigning the carbon-12 atom a mass of 12 atomic mass units (a

Stvx, Give the styx code of b4h10 and which type of bond present in it?

Give the styx code of b4h10 and which type of bond present in it?

Draw a typical triglyceride, Draw a  typical triglyceride and name its bui...

Draw a  typical triglyceride and name its building blocks. Mark centres of chirality.   The reaction cascade exact to fatty acid degradation is called "β-oxidation". It take

Prefixes, why we consider methyl using prefixes?

why we consider methyl using prefixes?

The following for which one mathematical expression, Among the following fo...

Among the following for which one mathematical expression γ= h/p  stands: (1) De Broglie equation (2) Einstein equation (3) Uncertainty equation (4) Bohr equation A

Lead acetate test, what is the confirmatory test for acid radical(so42-)

what is the confirmatory test for acid radical(so42-)

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd