What is it about?
Density functional theory (DFT) calculations and natural population analysis (NPA) performed on metallocenes of Fe, Ru and Os triad reveal that the cyclo-P5 ligand introduces basicity at the metal center. All-electron calculations at the B3LYP/6-311+G* level yield NPA charges of 0.28, −0.28 and −0.91 at the iron center in [FeCp2], [FeCp(η5-P5)] and [Fe(η5-P5)2], respectively. The accumulation of negative charge at the metal center is found to be similar in the cyclo-P5 analogues of ruthenocene and osmocene. Thus, for example, the net NPA charges on Ru and Os in the decaphosphametallocenes are predicted to be −0.6 to −0.9, respectively.
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Why is it important?
Our study reveals that there is transfer of small amount of electron density from each phosphorus atom to the metal center in the decaphospha metallocenes [M(η5-P5)2] , M=Fe, Ru, Os, leading to a significant build-up of negative charge on the metal. This is a new feature observed in the transition metals bound to cyclo-P5 ring. This finding is indeed supported by the indirect evidence observed by Scherer and co-workers from the diamagnetic behavior in an iridium derivative of Fe(P5), that the Fe atom is negatively charged while one of the P atoms is positively charged.
Perspectives
The extent of covalent bond formation between the metal and the ligand is more pronounced for the cyclo-P5 than the cyclopentadienyl ligand. Consequently, Cp retains 56−68% of aromaticity, the P5 ring exhibits 26−51% aromaticity as compared to the free anionic rings.
E.J. Padma Malar
University of Madras
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This page is a summary of: Can the cyclo‐P5 Ligand Introduce Basicity at the Transition Metal Center in Metallocenes? A Hybrid Density Functional Study on the cyclo‐P5 Analogues of Metallocenes of Fe, Ru and Os, European Journal of Inorganic Chemistry, June 2004, Wiley,
DOI: 10.1002/ejic.200400058.
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