Computational Methods: Transition Metal Clusters

Abstract

Cluster chemistry is dominated by structural aspects. Indeed, structure and bonding are strongly related to stability and properties, and cluster structures are particularly diverse and often complex. Thus, electron‐counting rules, which relate structure to electron count, have been the key to the development of cluster chemistry as a distinct area of chemistry. These rules have been set up progressively along time with the help of quantum chemistry. This article deals with the recent progress on transition metal and mixed main group/transition metal cluster chemistry arising from the contribution of modern computational theory to the rationalization of structures. This article focuses on “viable” species, i.e., molecules that are isolable under reasonable conditions and deals with the exploration of the limitations of the classical electron‐counting rules as well as the establishment of new rules for new structural types with the help of quantum chemical calculations.

Combined theoretical and time-resolved photoluminescence investigations of [Mo6Bri8Bra6]2−metal cluster units: evidence of dual emission

“…Thus we only optimized the atomic positions using the crystallographic cell parameters. Structural parameters resulting from these geometry optimizations are 31 From a qualitative point of view, the electronic structures of groups 6 and 7 transition metal M 6 clusters are very similar regardless of the nature of the capping and apical ligands: twelve molecular orbitals (MOs) mainly centered on metals have mainly a metalmetal bonding character and to a lesser extent a metal-ligand antibonding one. They are well separated from the antibonding MOs by a significant energy gap.…”

“…The first unoccupied MOs are the antibonding metalmetal MO counterparts, still presenting metal-ligand antibonding (d/p*) character. 31 The octahedral symmetry of the isolated [Mo 6 Br i 8 Br a 6 ] 2À unit is undoubtedly the ground state (S 0 ) structural arrangement (in vacuum at 0 K). Nevertheless, experimentally, the anisotropy of the cluster environment induces slight deviations from O h symmetry.…”

Metallacarboranes and their interactions: theoretical insights and their applicability

“…A review about computational methods on transition metal clusters highlights its importance for the understanding of structural cluster chemistry and how it supports each other with the classical electron counting rules. 3 General considerations to bear in mind in this section are that the calculations on the geometries of metallacarboranes agree fairly well with the experimental ones to within 0.01 Å or less for bond length differences, although bonds involving metal atoms show slightly larger discrepancies. NMR theoretical calculations are another extraordinary tool for structure elucidation and an entire section in this review is dedicated to it (see section 3.b).…”

“…There are several books covering the main topics of this review, such as transition metal clusters, 3 and more specific on borane based compounds, 4 to name a few examples.…”

“…3 The situation became crucial when some of the applications of metallacarboranes required a detailed understanding of their behavior, such as their surfactant properties in radionuclide extraction or non-covalent interactions with proteins in studies of their medicinal applications. These tasks enforced the use of special methodologies to study the interactions between metallacarboranes and their surroundings.…”