Question #77174

1 Answer
Jan 4, 2015

Answer:

dπ-pπ bonding is the formation of a π molecular orbital by the overlap of a d orbital on one atom with a #p# or #p"*"# orbital on another atom.

Explanation:

An example is the orbital overlap in a metal carbonyl such as Ni(CO)₄.

Usually, one atom supplies both electrons to the new bond. If the #d# orbital supplies the electrons, the process is called backbonding.

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Phosphorus does not form dπ-pπ bonds, because the #d# orbitals on P are too high in energy.

However, the lone-pair electrons in phosphines (R₃P) make good #σ# donors to the d orbitals of transition metals.

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Electron withdrawing groups lower the energies of the #σ"*"# orbitals. These antibonding orbitals can then act as backbonding #π# acceptors.

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PF₃ is almost as good an acceptor as CO. Phosphites [(RO)₃P] are about half as good as CO.