NEET Chemistry Notes Coordination Compounds – Complex or Coordination Compounds
Complex or Coordination Compounds
Complex or Coordination Compounds
Complex or coordination compounds are those molecular compounds which retain their identity in solid as well as in aqueous solution. In these compounds metal atoms are bound to a number of anions or neutral molecules by coordinate bonds. A part of these compounds is not dissociated in solution and its behaviour is different than its constituents.
The following are same terms related to coordination compounds given as: Definitions of some important terms pertaining to coordination compounds
Complex Ion
It is an electrically charged species in which central metal atom or ion is surrounded by number of ions or molecules.
Homoleptic and Heteroleptic Complexes
Complexes in which a metal is bound to only one kind of donor groups, e.g.. [Co(NH3)6]3+ are known as homoleptic. Complexes in which a metal is bound to more than one kind of donor groups, e.g.. [Co(NH3 ) 4Cl2 ]+, are known as heteroleptic.
Ligands
The ions or molecules bound to the central atom/ion in the coordination entity are called ligands.
Types of Ligands
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- Unidentate Ligand It is bound to a metal ion through a single donor atom.
- Unidentate Ligand It is bound to a metal ion through a single donor atom.
- Didentate of Bidentate Ligand It is bound to a metal ion through two donor atoms.
- Polydentate It is bound to a metal ion through several donor atoms, e.g. ethylene diamine tetraacetate ion [EDTA]4-.
- Ambidentate Ligands It can ligate through two different atoms,e.g. —N02,—ONO, —SCN,—NCS
- Chelate Ligands may be di or polydentate ligands which form closed ring with central metal ion. Closed ring is known as chelate ring and this process is called chelation.
More the number of chelate rings in a complex, complex will be more stable. The number of such ligating groups is called the denticity.
Coordination Number
The number of chemical bonds formed by the ligands with central metal atom or ion is called the coordination number of that complex.
Coordination Sphere
The central ion and the ligands attached to it are enclosed in square bracket which is known as coordination sphere. The ionisable group written outside the bracket is known as counter ions.
Coordination Polyhedron
The spatial arrangement of the ligands which are directly attached to the central atom or ion, is called coordination polyhedron around the central atom or ion. e.g. [Co (NH3)6]3+ is octahedral [Ni (CO)4] is tetrahedral
Oxidation Number of Central Atom
The charge of the complex if all the ligands are removed along with the electron pairs that are shared with the central atom, is called oxidation number of central atom.
e.g. onidation number of copper in [Cu(Cv)4]3- is + 1 and it is writen as Cu(I).
Magnetic Properties
The given complex compound is paramagnetic if one or more unpaired electrons are present in the d-subshell. If the complex does not contain any unpaired electron, is diamagnetic.
Magnetic moment,
Shapes
Shapes of coordination compounds depend upon hybridisation present in them