Periodic trends in metal–metal bonding in edge-shared [M2Cl10]4− systems

Abstract

Periodic trends in metal-metal interactions in edge-shared [M 2 Cl 10 ] 4À systems, involving the transition metals from groups 4 through 8 and electronic configurations ranging from d 1 d 1 through d 5 d 5 , have been investigated by calculating metal-metal bonding and spinpolarization (exchange) effects using density functional theory. The trends found in this study are compared with those for the analogous face-shared [M 2 Cl 9 ] 3À systems reported in earlier work. Strong linear correlations between the metal-metal bonding and spin-polarization terms have been obtained for all groups considered. In general, spin polarization and electron localization are predominant in 3d-3d species whereas electron delocalization and metal-metal bonding are favoured in 5d-5d species, with more variable results observed for 4d-4d systems. As previously found for face-shared [M 2 Cl 9 ] 3À systems, the strong correlations between the metal-metal bonding and spin polarization energy terms can be related to the fact that both properties appear to be similarly affected by the changes in the metal orbital properties and electron density occurring within the d n d n groups. A significant difference between the face-shared and edge-shared systems is that while the 4d metals in the former show a strong tendency for delocalized metal-metal bonded structures, the edge-shared counterparts display much greater variation with both metal-metal bonded and weakly coupled complexes observed. The tendency for weaker metal-metal interactions can be traced to the inability of the edge-shared bridging structure to accommodate the smaller metalmetal distances required for strong metal-metal bonding.

From WCl6 to WCl2: Properties of Intermediate Fe–W–Cl Phases

“…Calculations find that the δ level is destabilized through interactions with (μ 2 )-bridging halides (orbitals) of the same symmetry (Figure ). − Thereby the δ level is moved slightly above the δ* level. The electronic configuration of the ground state has been assigned as σ 2 π 2 δ* 2 by an analysis of the apparent metal–metal distance .…”

“MoCl3(dme)” Revisited: Improved Synthesis, Characterization, and X-ray and Electronic Structures

“…Stranger et al also found that the model predicted a metal valence orbital energy pattern for singlet [M 2 (μ-Cl) 2 Cl 8 ] 4– dimers of σ 2 π 2 δ* 2 δ 0 π* 0 σ* 0 rather than the expected σ 2 π 2 δ 2 δ* 0 π* 0 σ* 0 pattern. − This atypical configuration was first examined in a general sense by Hoffmann et al and in more detail for [Mo 2 (μ-Cl) 2 Cl 8 ] 4– by Cotton and Feng and arises from destabilization of the δ orbital by interaction with orbitals on the bridging halides. To explore the question of whether Mo 2 (μ-Cl) 2 Cl 4 (dme) 2 is more like the decachloride tetra-anion or the phosphine-containing dimers, we optimized D 2 h -[Mo 2 (μ-Cl) 2 Cl 8 ] 4– , C 2 h -[Mo 2 (μ-Cl) 2 Cl 6 (axial-OH 2 ) 2 ] 2– , and C 2 -[Mo 2 (μ-Cl) 2 Cl 6 (equatorial-OH 2 ) 2 ] 2– as spin singlets using the BLYP/def2-TZVP model chemistry.…”

Metal–Metal Bonding in Trinuclear, Mixed-Valence [Ti3X12]4– (X = F, Cl, Br, I) Face-Shared Complexes

“…In previous work, − largely focused on face-shared [M 2 X 9 ] z − and edge-shared [M 2 X 10 ] z‑ dinuclear systems, we have shown that a satisfactory description of the entire range of metal–metal interactions can be achieved with an approach based on the analysis of the BS potential energy curve in terms of the curves for the associated spin states. The latter states result when one or more subsets of metal-based electrons are involved in metal–metal bonding while the remaining electrons are weakly coupled.…”

“…Recently, we investigated the electronic structure and metal–metal bonding in the linear trinuclear [Mo 3 X 12 ] 3– (X = F, Cl, Br, I) system using density functional theory (DFT) in combination with the broken-symmetry approach of Noodleman and co-workers. , In the past we used a similar approach to investigate a diverse series of related dinuclear face-shared [M 2 X 9 ] z − and edge-shared [M 2 X 10 ] z − systems and showed that this methodology was capable of describing the entire range of metal–metal interactions from weak antiferromagnetic coupling through to multiple metal–metal bonding. − In our study of the trinuclear [Mo 3 X 12 ] 3– system, we also examined the possibility of bond-stretch isomerism and, consequently, the existence of both symmetric ( D 3 d ) and unsymmetric ( C 3 v ) forms of these complexes as shown in Scheme . In the symmetric form, the metal–metal distances are identical, whereas the unsymmetric structure has one short and one long metal–metal distance.…”