Justification Of Hsab Principle

A number of theories have been proposed to explain the tendency of hared acids to prefer hare dbases and soft acids to prefer soft bases.

1.    Electrostatic Interaction. An explanation of preferential combination of hard-acid hard base may be attributed purely to electrostatic or ionic interaction. For example hard acid such as H⁺, Li⁺, Na+ and hard bases such as OH^-, O^2-, F^- are known to form ionic compounds. Smaller the ions, lesser the intrinsic distance and greater will be the attraction and stability of the resulting complex formed by the hared acid and hared base.

2.    Polarizing power and polarzability. Electrostatic interactions cannot accent for the stability or large sized soft acid-soft base compounds. As the size of the soft ions is comparatively bigger there is a large degree of covalence in their interaction. For example of soft acids like Cu+, Ag⁺, Cd²⁺ form strong compounds with soft bases like CI^- , I^- which have considerable covalent character. Most of the soft acids are transition metals containing six or more d electrons. As these d electrons have great polarizing power, soft bases like I-, S^2-get easily polarized and therefore their interacting brings a lot covalent character in their interactions.

3.  π  bonding contribution . π bonding between soft acids of transition metals in low oxidation states and soft bases such as CO, phosphates (R₃ P) alkenes, alkynes etc. contributes considerably towards the stability of the soft acid-soft base compound formed. Sigma bond formation due to donation of electrons from the base to metal is reinforced by π – back donation form metal to the base.

For more help in Justification Of Hsab Principle click the button below to submit your homework assignment