Imaging an unsupported metal–metal bond in dirhenium molecules at the atomic scale

Abstract

Metallic bonds remain one of the most important and least understood of the chemical bonds. In this study, we generated Re2 molecules in which the Re–Re core is unsupported by ligands. Real-time imaging of the atomic-scale dynamics of Re2 adsorbed on a graphitic lattice allows direct measurement of Re–Re bond lengths for individual molecules that changes in discrete steps correlating with bond order from one to four. Direct imaging of the Re–Re bond breaking process reveals a new bonding state with the bond order less than one and a high-amplitude vibrational stretch, preceding the bond dissociation. The methodology, based on aberration-corrected transmission electron microscopy imaging, is shown to be a powerful analytical tool for the investigation of dynamics of metallic bonding at the atomic level.

Supported Metal Pair-Site Catalysts

“…to identify a method that provides sufficient agreement with experiments. For example, Cao et al 61 screened a variety of functionals (e.g., PBE, BLYP, and M06-L), effective core potentials (e.g., LANL2DZ, SRSC), and basis sets (def2-SVP, def-TZVP)…”

All Eyes on atoms

“…Rhenium atoms have the advantage of being so heavy and large that they can be readily observed by electron microscopy. 2 Chemists analysing complexes built around a pair of rhenium atoms had previously formulated dirhenium compounds with a broad range of different Re-Re bonds, from single to quintuple bonds. Kaiser and Khlobystov were now able to watch a pair of rhenium atoms undergoing transitions between these different binding states, as well as the breaking and renewed formation of the single bond.…”

Inference to the Best Explanation

“…There can be little doubt that chemical bonds (of some kind) do have physical objectivity or else macroscopic matter (including biological organisms) would not exist. Moreover, the objectivity of chemical bonds is now well established by the empirical data collected from a variety of experiments (see Shin et al 2002;Friedrich 2018;Wilson et al 2019;Hu et al 2019;Cao et al 2020), as frankly expressed by Valerio Magnasco: "Experimental evidence shows that molecules [...] have a structure made of bonds [...]" (Magnasco 2010, xi).…”