|Class 12 Chemistry Coordination Compounds||Denticity|
it determines the total number of donor atoms in a molecule.
On the basis of the property denticity ligands are :
Examples : CN-, OH-,Cl-,Br-,NH3:,H2O,CO etc
(ethylene diamine )
Hexadentate: ethylene diamine tetra acetic acid (EDTA)
chelate: when the ligand has two or more donor atoms and they are arranged in such a way that they give rise to a ring like structure than the effect is called chelating and the ring formed is chelate .
uses of chelates:
Ambidentate ligand: that have two donor atoms but doesn’t show chelation. This group bond at a time by one atom.
For example: CN-,NO2 etc
Symmetrical and unsymmetrical ligands :
Symmetrical ligands: if ligands attached to central atom are of same type
Example: ethylenediamine etc.
Unsymmetrical ligands: if ligands attached are of different type.
Example: glycinate ion etc.
Coordination number: it is the number of ligands bonded with the central metal atom for example: IN [Ag (CN)2]-“the no. Of ligands attached are 2 therefore coordination no. is 2 “.
Oxidation number: it is the residual chargeleft on the atom when all other atoms are removed from it .it is calculated by assigning appropriate charges to ligands and then equating the sum of the charges on the central atom and the ligands equal to the charge on the coordination sphere.
For example: [Co (NH3)6] Cl3 in this oxidation state of NH3 is 0 and for Cl is -1, and ooxidation state of Co is taken as x then
(x-3) x 1=0 or x=+3
another example: [Cu (CN)4]3- in this oxidation state of Cu is taken as x, CN as -1 so,
x + (-1 X 4) = -3 or x=+1
Homo-leptic and hetero-leptic compounds
Homoleptic: are those which have same kind of ligands attached to central metal atom
Example:in [Co (NH3)6] Cl3 is homoleptic as ligands are same
terolyptic: when ligands attached are of different type
Example: in [CoCl3(NH3)3]3+ is heterolytic because ligands attached are of different types.