Small molecule activation with divalent samarium triflate: a synergistic effort to cleave O₂

Abstract

The divalent samarium triflate salt does not react with CO2 or water, but does react with traces of O2 or N2O to form a tetrameric bis-oxo samarium motif. The reaction with O2 is a 4e- reductive cleavage where the electrons are coming from four different samarium centers. This highlights a rare synergistic effect for cleaving O2, which has no precedent in divalent lanthanide complexes. Additionally, the addition of CO2 to the tetrameric bis-oxo intermediate leads to the formation of a tetrameric bis-carbonate samarium triflate. Thus, the concomitant reaction of CO2 with traces of O2 leads to the same bis-carbonate tetrameric assembly.

[Sm6O4(cbz)10(thf)6]·2C7H8: A Polynuclear Samarium Oxo Cluster Obtained from Carbazole-Driven Oxidation of Samarium Nanoparticles

“…Herein, four triple-bridged oxygen atoms occur and exhibit Sm–O distances of 219.4(1)-235.7(1) pm. These distances are well-comparable with μ 3 -bridged O 2– atoms in samarium­(III) coordination compounds (220.7–227.1 pm) , and Sm–O distances in the binary oxide Sm 2 O 3 (231.8–240.3 pm) . The shortest Sm–O distance (217.8(1) pm) occurs for the terminal Sm atoms of the Sm 6 O 4 core, which are not part of Sm 2 O 2 quadrangles.…”

Facile Dinitrogen and Dioxygen Cleavage by a Uranium(III) Complex: Cooperativity Between the Non‐Innocent Ligand and the Uranium Center

“…Such ahigh stabilization has been found in the reaction of divalent samarium with O 2 . [69] In this intermediate (C), the O 2 molecule has been doubly reduced, as evidenced by the O À Obond distance of 1.51 (1.20 in free O 2 ), so that the two uranium centers are oxidized to the + IV state.T he OÀO bond is thus broken with alow barrier (13.9 kcal mol À1 )inthe TS2,w hich is similar to the TS1 found for the NÀNb ond breaking as it involves the two phosphorus atoms.Geometrically,t he TS2 appears to be symmetrical with the two P-O distances of 2.15 (vs.2 .18/2.20 for P À Nb onds in TS1). TheO À Obond is already broken (2.57 ).…”

High-Frequency and -Field Electron Paramagnetic Resonance Spectroscopic Analysis of Metal–Ligand Covalency in a 4f7 Valence Series (Eu2+, Gd3+, and Tb4+)

“…The accessible molecular oxidation states of the lanthanides have rapidly expanded. − The synthesis and characterization of novel divalent complexes has enabled a detailed understanding of lanthanide electronic structure − and reactivity, − and, as a result, has demonstrated significant opportunities to improve our knowledge of the magnetic properties of the lanthanides. − Until 2019, molecular tetravalent lanthanide complexes were limited to cerium. − Recently developed weak-field ligand systems, such as imidophosphoranes [NP­(NR 2 ) 3 ] − (R = alkyl), decrease the thermodynamic barrier for oxidation, thereby making the oxidation potential more accessible within the solvent window. , We have recently reported the synthesis and characterization of novel lanthanide complexes featuring weak-field dialkylamide imidophosphorane ligands. This class of compounds includes the most reducing Ce 3+ complex to date as well as one of the first isolable Tb 4+ complexes.…”