QTAIM analysis of the bonding in anionic group 6 carbonyl selenide clusters: [Se2M3(CO)10]2- (M=Cr, Mo, W)

Abstract

Context

This research aims to offer a deeper understanding of the bonding interactions between M-Se and M-CO and how these interactions change across the group 6 transition metal series: [Se₂M₃(CO)₁₀]^2- (M = Cr, Mo, W). It also seeks to explore the impact of carbonyl groups on M-M interactions within the clusters. Seven criteria, which are based on QTAIM properties, have been considered and compared with the corresponding criteria in other transition metal clusters. The results confirm that no such bond critical points or bond baths occur between transition metals, which instead have 5c–7e bonding interactions delocalized over their five-membered M₃(μ-Se)₂ ring, as evidenced by the non-negligible nonbonding delocalization indices. The topological properties of three bond clusters, Cr-Se, Mo-Se, and W-Se, resemble those of “intermediate closed shell characters,” which combine covalent and electrostatic properties. Source function calculations indicated that the bonded Se atom contributed the most to each Cr-Se and Mo-Se bcp. The O_CO atoms and nonbonded Se atoms also contributed to some extent. However, metal atoms act as sinks rather than as sources of electron density. In contrast, the majority of the metal atoms, both bonded and nonbonded, contribute to Cr-W bcps. Analysis of the delocalization indices δ(M…O) in the three clusters indicates that CO significantly contributes to Cr π-back donation in cluster 1. In contrast, no π-back donation occurs from CO to Mo or W in clusters 2 or 3, respectively.

Methods

The B3P86 hybrid functional was used for computations in the Gaussian 09 software. The LanL2DZ basis set was employed for Cr, Mo, and W, while the 6-31G (d, p) basis set was used for C, O, and Se atoms. We performed QTAIM analysis using the AIM2000 and Multiwfn packages, incorporating B3P86/WTBS for Cr, Mo, and W atoms. The 6-311++G(3df,3pd) basis set was used for C, O, and Se atoms. Additionally, we utilized the ELF and SF.