The paper provided by Radwan is a good and detailed answer.
In short, phosphines with electronegative or electron-poor substituents have antibonding (sigma*) orbitals (for instance P-F sigma star bonds), which are well positioned in space and energy to mix with d orbitals on a ligated metal center.
The paper provided by Radwan is a good and detailed answer.
In short, phosphines with electronegative or electron-poor substituents have antibonding (sigma*) orbitals (for instance P-F sigma star bonds), which are well positioned in space and energy to mix with d orbitals on a ligated metal center.
It is well known that PF3 is considered as sigma donor and pi acceptor. I have had a look at the paper introduced by Radwan, in which the orbital of P atom in PR3 molecule which is involved in pi accepting was taken as 3p orbital. I am not convinced that why 3d orbitals of phosphorous are not considered as the orbitals which overlap with suitable d orbitals of the transition metal.Also,the 3p orbitals of the P atom in PR3 molecule are involved in bonding with the terminal atoms, such as F atoms how can they overlap with the d orbitals of the central metal?.
Mohammad (and others), one of the difficulties we older folks have is continuing to want to view bonding from simple, valence bond pictures. I have had students in advanced inorganic classes use Gaussian, at an appropriate level and with appropriate basis sets, to calculate PF3 MOs and PF3 Cr(CO)5 complexes. They are surprised (as was I the first time I did the calculations) to find that the orbitals involved in bonding are true molecular orbitals whose components may have little d orbital character. The same is true when one calculates molecules such as SiF6(-2).
Dear Alif the answer found in the link
https://www.ncbi.nlm.nih.gov/pubmed/20014798
Thanks a lot Prof. Merola for the valuable information. I, in fact,had seen similar case for PF5, in which the involvement of d orbitals is negligible.
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