Notes On Metal Carbonyls And Stability Of Coordination Compounds - CBSE Class 12 Chemistry
Carbonyls are coordination compounds of transition metals with carbon monoxide. Depending on the number of metal atoms, carbonyls are divided into two types: mono-meric (or) mononuclear carbonyls and poly-nuclear carbonyls. Mononuclear carbonyls contain one metal atom per molecule. Ex: Ex: Ni(CO)4, Fe(CO)5, Cr(CO)6...etc Poly-nuclear carbonyls contain two (or) more than two metal atoms per molecule. Ex: Mn2(CO)10, Co2(CO)8 In carbonyls, the oxidation state of metal is zero. Carbonyls have simple and well-defined structures. Ex: Ni(CO)4 has tetrahedral geometry, Fe(CO)5 has trigonal bipyramidal, and Cr(CO)6 has octahedral geometry. The stability of a complex in a solution refers to the degree of association between the metal ion and the ligands involved in the state of equilibrium. Transition metal complex ions differ considerably in their stability. Their relative stability can be expressed in terms of an equilibrium constant, called the stability constant. The greater the value of stability constant, more stable is the complex. The reciprocal of the formation constant is known as the instability constant or the dissociation constant. The reaction between the metal ion and the ligand may be represented as, Metal ions are usually surrounded by solvent molecules that will compete with the ligand molecules and be successively replaced by them.

#### Summary

Carbonyls are coordination compounds of transition metals with carbon monoxide. Depending on the number of metal atoms, carbonyls are divided into two types: mono-meric (or) mononuclear carbonyls and poly-nuclear carbonyls. Mononuclear carbonyls contain one metal atom per molecule. Ex: Ex: Ni(CO)4, Fe(CO)5, Cr(CO)6...etc Poly-nuclear carbonyls contain two (or) more than two metal atoms per molecule. Ex: Mn2(CO)10, Co2(CO)8 In carbonyls, the oxidation state of metal is zero. Carbonyls have simple and well-defined structures. Ex: Ni(CO)4 has tetrahedral geometry, Fe(CO)5 has trigonal bipyramidal, and Cr(CO)6 has octahedral geometry. The stability of a complex in a solution refers to the degree of association between the metal ion and the ligands involved in the state of equilibrium. Transition metal complex ions differ considerably in their stability. Their relative stability can be expressed in terms of an equilibrium constant, called the stability constant. The greater the value of stability constant, more stable is the complex. The reciprocal of the formation constant is known as the instability constant or the dissociation constant. The reaction between the metal ion and the ligand may be represented as, Metal ions are usually surrounded by solvent molecules that will compete with the ligand molecules and be successively replaced by them.

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