Rare‐Earth Metal(II) Aryloxides: Structure, Synthesis, and EPR Spectroscopy of [K(2.2.2‐cryptand)][Sc(OC₆H₂tBu₂‐2,6‐Me‐4)₃]

Abstract

The suitability of aryloxide ligands for stabilizing +2 oxidation states of Sc and Y has been examined and EPR evidence indicating the first O-donor complexes of Sc and Y has been obtained, as well as an X-ray crystal structure of a Sc aryloxide complex. The trivalent rare-earth metal aryloxide precursors, Ln(OAr') , 1-Ln (Ln=Sc, Y, Gd, Dy, Ho, Er; OAr'=OC H tBu -2,6-Me-4), were synthesized from the corresponding rare-earth metal trichlorides and LiOAr'⋅OEt . Reduction of THF solutions of 1-Ln with potassium graphite in the presence of 2.2.2-cryptand (crypt) yielded dark-colored solutions, 2-Ln, whose EPR spectra at 77 K are characteristic of the Ln ions: a two-line spectrum (g =1.99, g =1.97, A =154 G) for 2-Y and an eight-line spectrum (g =2.01 and A =291 G) for 2-Sc. Solutions of 2-Y decompose within one minute at room temperature, wheras 2-Sc persists up to 40 min at room temperature. 2-Sc was identified by X-ray crystallography as [K(crypt)][Sc(OAr') ], which has a trigonal-planar arrangement of oxygen-donor atoms around Sc . Analogous reductions of 1-Ln for Ln=Gd, Dy, Ho, and Er also gave dark solutions of limited stability. Theoretical analysis using time-dependent density functional theory (TD-DFT) along with complete active space self-consistent field (CASSCF) methods, and structural analysis with the Guzei ligand solid angle G-parameter method are presented.

Mononuclear Dysprosium Alkoxide and Aryloxide Single‐Molecule Magnets

“…A perfect C 3 h symmetry would eliminate all the transverse CF terms except the sixth‐order transverse anisotropy q =±6, thereby restricting QTM [35] . Bulky aryloxide ligands have demonstrated their effectiveness for stabilising three‐coordinate Ln complexes [111, 112] . However, in the literature, there are only three CN3 mononuclear Er III SMMs reported to date [111, 113] (Figure 18).…”

“…[35] Bulky aryloxide ligands have demonstrated their effectiveness for stabilising three-coordinate Ln complexes. [111,112] However,i nt he literature, there are only three CN3 mononuclear Er III SMMs reported to date [111,113] (Figure 18). [Er{N(SiMe 3 ) 2 } 3 ]( 1-Er)w as the first mononuclear three-coordinateE r III SMM to be reported; [113] althought his complex was first synthesised by Bradley in [16] Figure 18.…”

Evaluating Electron‐Transfer Reactivity of Complexes of Actinides in +2 and +3 Oxidation States by using EPR Spectroscopy

“…[23][24][25] Sincet he recently discovered + 2i ons can all be generated by reduction using alkali metals, it appearst he reduction potentials are less negative than the À2.86 Vv s. Fc + /Fc, the potential of Na. [29] Due to the difficulty of electrochemical characterization in our hands (see examples of fluoride abstraction, [20] activation of solvent, [30] andt hermali nstability of Ln II compounds generated by chemical means [31] ), we soughtt od etermine if as eries of chemical reduction reactions could be used to characterize the relative reduction potentials of the new compounds. [28] Recently,I nman and Cloke have reported Th IV /Th III reduction potentials for four compounds to be between À3.32 and À2.96 V( vs. Fc + /Fc in 0.05 m [nBu 4 N][BPh 4 ]i nT HF).…”

Distinct Reactivity of Trimethylytterbium toward AlMe3 and GaMe3: Synthesis of Donor‐Stabilized Dimethylytterbium

“…KC 8 was synthesized according to a literature procedure [27] . The reduction reactions with potassium graphite were performed according to a published procedure [28] . [LuMe 3 ] n was synthesized according to a published procedure [29] .…”