A step by step structural transformation of Ru-Ru bonding unit from paddle-wheel to edge-sharing bi-octahedra configuration

Abstract

The structural transformation of metal-metal bonding dimer induced by external stimuli is of scientific significance in terms of both M-M compounds synthesis and reactivity. This paper reported the transformation stimulated by Et3N from paddle-wheel Ru2(CH3CO2)4+ with a typical open-shell electronic configuration σ2π4δ2π*2δ* to Ru2(CH3CO2)2(CH3O)2(hfac)2 (2) (hfac = hexafluoroacetylacetonate) undergoing a stable asymmetric intermediate Ru2(CH3CO2)2(CH3O)3(hfac)(CH3OH) (1), and both compounds 1 and 2 exhibit a edge-sharing bi-octahedra (ESBO) characteristic close-shell electronic configuration σ2π2δ2δ*2π*2. The evolution of solution species revealed by temperature- and time-dependent electrospray ionization mass spectrometry (ESI-MS) suggests a step by step transformation mechanism, convincing that the Ru2 dimer can adapt to changes in metal-metal bonding type and oxidation state without undergoing dissociation to monomeric Ru fragments. This is the first mechanism exploration of the M-M dimer structural transformation study using ESI-MS. The results not only reveal the important reactivity of dimetal carboxylates with ligands exchanging, but also deep understand the conversion mechanism of M-M multiple bonds type affected by the coordination environment