Structure and Reactivity of Polynuclear Divalent Lanthanide Disiloxanediolate Complexes

Abstract

Trinuclear molecular complexes of europium (II) and ytterbium­(II) [Ln3{(Ph2SiO)2O}3(THF)6], 1-Ln 3 L 3 (Ln = Eu and Yb), supported by the dianionic tetraphenyl disiloxanediolate ligand, were synthesized via protonolysis of the [Ln­{N­(SiMe3)2}2(THF)2] complexes. In contrast, the reaction of [Sm­{N­(SiMe3)2}2(THF)2] with the (Ph2SiOH)2O ligand led to the isolation of the mixed-valent Sm­(II)/Sm­(III) complex [Sm3{(Ph2SiO)2O}3{N­(SiMe3)2}­(THF)4], 2-Sm 3 L 3 , which was crystallographically characterized. The Eu­(II) complex 1-Eu 3 L 3 displays weak ferromagnetic coupling between the Eu­(II) metal centers (J = 0.1035 cm–1). The addition of 3 equiv of (Ph2SiOK)2O to 1-Eu 3 L 3 resulted in the formation of the polynuclear Eu­(II) dimer of dimers [K4Eu2{(Ph2SiO)2O}4(Et2O)2]2, 3-Eu 2 L 4 . Complexes 1-Ln 3 L 3 (Ln = Eu and Yb) are stable in solution at room temperature, while 3-Eu 2L4 shows higher reactivity and rapidly decomposes to give the mixed-valent Eu­(II)/Eu­(III) species [K3Eu2{(Ph2SiO)2O}4], 4-Eu 2 L 4 . Complex 1-Yb 3 L 3 affects the slow reductive disproportionation of carbon dioxide, but 1-Eu 3 L 3 does not display any reactivity toward CO2. However, the presence of one additional (Ph2SiO–)2O per Eu­(II) metal center in 3-Eu 2 L 4 increases dramatically the reductive ability of the Eu­(II) metal centers, affording the first example of carbon dioxide activation by an isolated divalent europium complex. The reduction of CO2 by 3-Eu 2 L 4 is immediate, and carbonate is formed selectively after the addition of a stoichiometric amount of CO2.

Isolation and redox reactivity of cerium complexes in four redox states

“… 26 In previous studies the reduction of CO 2 by Sm( ii ) Yb( ii ) or Eu( ii ) complexes led either to carbonate alone 27 or to a mixture of carbonate and oxalate depending on the supporting ligand. 28 …”

Tetrameric cubane Al 9Ln 7 (Ln = Ce, Pr, Nd) clusters as aldol addition catalysts

“…In this study, we report the synthesis, structures, and catalytic performance of various tetrameric cubane cluster compounds using carboxylates. Although the [Ln 4 (μ 3 -OH) 4 ] 8+ cubane-like configuration [23][24][25][26][27] is common and heterometallic hybridized cubane-like conformation compounds have been reported, this is the first report of heterometallic cubanes coupled with lanthanides with group 13 metals. Notably, the main group metal aluminum and the light rare metal served as a co-metal source, 3aminobenzoic acid was chosen as the ligand, and pyridine was introduced to adjust the pH of the reaction system.…”

Low-Valent Transition Metalate Anions in Synthesis, Small Molecule Activation, and Catalysis

“…Examples for 4d- and 5d-transition metalates are therefore included throughout this review. A number of metalates are known for the lanthanides and actinides. − However, their chemistry is often distinct due to the more electropositive nature of these elements, and the more core-like character of the f orbitals, which gives rise to less directional, and more electrostatic, bonding. Due to the redox-active nature of the ligands, the oxidation state of the metal cations can be debatable in some cases.…”