Abstract
A density functional study of {η2-(X@Cn)}ML2 complexes with various cage sizes (C60, C70, C76, C84, C90, C96), encapsulated ions (X = F−, 0, Li+) and metal fragments (M = Pt, Pd) is performed, using M06/LANL2DZ levels of theory. The importance of π back-bonding to the thermodynamic stability of fullerene-transition metal complexes ({η2-(X@Cn)}ML2) and the effect of encapsulated ions, metal fragments and cage sizes on the π back-bonding are determined in this study. The theoretical computations suggest that π back-bonding plays an essential role in the formation of fullerene-transition metal complexes. The theoretical evidence also suggests that there is no linear correlation between cage sizes and π back-bonding, but the encapsulated Li+ ion enhances π back-bonding and F− ion results in its deterioration. These computations also show that a platinum center produces stronger π back-bonding than a palladium center. It is hoped that the conclusions that are provided by this study can be used in the design, synthesis and growth of novel fullerene-transition complexes.
Highlights
The first fullerene-transition metal complex, (η2-C60)Pt(Ph3)2, was prepared and structurally characterized by Fagan et al in 1991 [1]
The strength of the π back-bonding strength is estimated from an energetic viewpoint using an advanced energy decomposition analysis (EDA) method. This analysis shows the effect of encapsulated ions, metal fragments and cage sizes on π back-bonding
The calculations show the reaction is more stable when the Li+ ion is encapsulated within Cn but the complex becomes unstable if there is a F− ion
Summary
The first fullerene-transition metal complex, (η2-C60)Pt(Ph3), was prepared and structurally characterized by Fagan et al in 1991 [1]. It was the starting point for a new class of study for fullerene chemistry. Understanding the strength and nature of metal-ligand bonding is crucial for the design of new fullerene-transition metal complexes because the structure and stability of various intermediates are important to the formation of organometallics [9]. In an earlier work by the authors [10], {η2-(X@C60)}ML2 complexes (M = Pt, Pd; X = 0, Li+, L = PPh3) were studied and it was found that there is a relationship between thermodynamic stability and π backbonding; that is, the greater the π back-bonding, the greater is thermodynamic stability. The following reactions are studied: ML2 + X @ Cn → {η2 ‐(X @ Cn)} ML2
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