Answer to Question #24229 in Physical Chemistry for naeim vhora

Question

what is '3c-2e' bridge? explain the que. with using:Al2H6,Al2(C6H5)6
what is '3c-4e' bridge? explain the que. with using:Al2Cl6,Be2Cl4,I2Cl6,SnCl2 and also show hybridization in the examples like sp3-sp3-sp3.

Answer 1

A three-center two-electron bond is an electron-deficient chemical bond where three atoms share two electrons. The combination of three atomic orbitals form three molecular orbitals: one bonding, one non-bonding, and one anti-bonding. The two electrons go into the bonding orbital, resulting in a net bonding effect and constituting a chemical bond among all three atoms. In many common bonds of this type, the bonding orbital is shifted towards two of the three atoms instead of being spread equally among all three. The simplest example of a 3c-2e bond is in the trihydrogen cation, H⁺

H H H
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Al Al
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H H H

C6H5 C6H5 C6H5
/
/
Al Al
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C6H5 C6H5 C6H5

The 3-center 4-electron bond is a model used to explain bonding in hypervalent molecules such as phosphorus pentafluoride, sulfur hexafluoride, the xenon fluorides, and the bifluoride ion; it is also used to explain pi bonding in molecules such as ozone, carboxylates and amides. It is also known as the Pimentel–Rundle three-center model after the work published by George C. Pimentel in 1951,[3] which built on concepts developed earlier by Robert E. Rundle for electron-deficient bonding

Cl Cl Cl
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Al Al
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Cl Cl Cl

Cl
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Cl- Be Be-Cl
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Cl