* FLEXIDENTATE CHARACTER OF POLYDENTATE LIGANDS ;
* Poly dentate ligands have flexi dentate character in the sense that all givers atoms may non organize co-ordinate bonds with the cardinal metal atom or ion. For illustration ; EDTA which is the hexa dentate ligand besides acts as tetra dentate or penta dentate in certain composites. Similarly sulphate ion. which is a bi dentate ligand. besides acts as a glandular fever dentate ligand in certain composites. e. g. in [ Co ( SO4 ) ( NH3 ) 5 ] Cl. * LABILE COMPLEXES ;
* A composite in which the ligands can be easy replaced by other ligands is called a labile composite. * GEOMETRY OF [ CuX4 ] 2- IONS ;
* The halide composite of Cu ( 2 ) shows two different stereo chemical sciences. In ( NH4 ) 2 [ CuCl4 ] . [ CuCl4 ] 2- ion is square planar. but Cs2 [ CuCl4 ] and Cs2 [ CuBr4 ] . the [ CuX4 ] 2- ions have a somewhat squashed tetrahedral form. Tetrahedral [ CuCl4 ] 2- ions are orangish whereas. square planar [ CuCl4 ] 2- ions are xanthous in coloring material. * GREATER STABILITY OF Co ( +3 ) COMPLEXES THAN Co ( +2 ) COMPLEXES ; * Co+2 ions are really stable & A ; are hard to oxidize. Co+3 ions are less stable and are readily reduced by H2O to Co2+ . In contrast Co ( +2 ) are less stable and are readily oxidised to Co ( +3 ) composite. i. e. Co ( 3 ) are really stable. This is because CFSE of Co ( +3 ) with d6 constellation is higher than Co ( +2 ) with d7 constellation. * SIDGWICK THEORY OR EFFECTIVE ATOMIC NUMBER ( EAN ) RULE ;
* Sidgwick put forward a regulation to explicate the stableness of composites on the footing of effectual atomic figure as follows: – EAN of metal in complex= atomic figure –oxidation state+2? co-ordination figure A stable composite is formed if the EAN is equal to the atomic figure of the following baronial gas.
Therefore. from the computation given in the tabular array below. [ Fe ( CN ) 6 ] 4- is more stable than [ Fe ( CN ) 6 ] 3- Though this regulation is found to be applicable in many instances. yet it fails in no. Of instances as illustrated by last two illustrations given in the tabular array below:
complex| Oxidation state| Atomic figure | Co-ordination number| EAN| [ Co ( NH3 ) 6 ] 3+| +3| 27| 6| 27-3+2?6=36. i. e. [ Kr ] |
[ Fe ( CN ) 6 ] 4-| +2| 26| 6| 26-2+2?6=36. i. e. [ Kr ] |
[ PtCl6 ] 2-| +4| 78| 6| 78-4+2?6=86. i. e. [ Rn ] |
[ Fe ( CN ) 6 ] 3-| +3| 26| 6| 26-3+2?6=35|
[ Ag ( NH3 ) 2 ] 1+| +1| 47| 2| 47-1+2?2=50|
