Optimizing Alkali Metal (M) and Chelate (L) Combinations for the Synthesis and Stability of [M(L)][(C₅H₄SiMe₃)₃Y] Yttrium(II) Complexes

Abstract

To optimize the factors affecting the generation and stability of [M­(L)]­[Cp′3YII] complexes (Cp′ = C5H4SiMe3), reductions of Cp′3YIII with nine different combinations of alkali metals (M = Li, Na, K, Rb, Cs) and chelating agents (L = 2.2.2-cryptand, 18-crown-6, and dibenzo-18-crown-6) have been examined. The thermal decomposition of each [M­(L)]­[Cp′3YII] product in THF at room temperature was monitored via UV–vis spectra collected over time, and the decomposition profiles were compared. The most stable M/L combination was found to be [K­(crypt)]­[Cp′3YII] with a decomposition t 1/2 ≈ 71 ± 7 min at an 80 mM concentration. The reduction reaction that generates [K­(18-crown-6)]­[Cp′3YII] can be cleanly reversed by addition of Hg to generate the starting materials, Cp′3YIII and 18-crown-6, and potassium mercury amalgam.

A rare isocyanide derived from an unprecedented neutral yttrium(ii) bis(amide) complex

“…The first Y( ii ) complex, {Y(C 5 H 4 SiMe 3 ) 3 } − , was prepared by reduction of the neutral Y( iii ) complex (Chart 1), and the stability of these complexes is closely tied to the counterion used. 2–4 Recently, an Y( ii ) complex using tris(aryloxide)mesitylene ligands was reported by Meyer and Evans that is stable for ∼48 h at room temperature in THF. 5,6 In addition to cyclopentadienyl and alkoxide ligands, hexamethyldisilazides have been employed.…”

Reduction of Rare-Earth Metal Complexes Induced by γ Irradiation

“…The Ln­(III) compounds Sc III (NR 2 ) 3 , Cp 3 ′ Y III , and Cp 3 ′ La III (R = SiMe 3 , Cp′ = C 5 H 4 SiMe 3 ) were chosen to probe the viability of the method since their corresponding Ln­(II) compounds have been chemically isolated, exhibit distinctive EPR spectra, and have UV–visible spectra with distinctive absorptions. ,,, The known EPR spectra of [Sc II (NR 2 ) 3 ] 1– and [Cp 3 ′ La II ] 1– were clearly discernible even in the presence of the irradiated solvent peak, Figure , Table , but the hyperfine coupling ( A ) of [Cp 3 ′ Y II ] 1– was unresolved under these conditions (Figure S5). However, the UV–visible spectra for the Ln­(II) species generated from γ irradiation of these compounds in all cases were consistent with those generated from chemical reduction, Figure , Table .…”

“…Given the particularly good agreement between the electronic absorption spectrum of [Cp 3 ′ Y II ] 1– prepared by either chemical reduction or γ irradiation and the fact that the spectra of many different salts of [Cp 3 ′ Y II ] 1– are identical regardless of the cation present, the absorption at 530 nm of [Cp 3 ′ Y II ] 1– was used to monitor the growth of Y­(II) with increasing dosages of γ irradiation. ,, A path length of 0.3 cm was determined experimentally using fluorenone as a known standard (see Figure S6). Additionally, different starting concentrations (0.075 vs 0.15 M) of the Y­(III) complex Cp 3 ′ Y III were used to determine if this affected the rate of Y­(II) formation.…”

“…One of the major advances in the chemistry of the rare-earth elements (Ln), that is, scandium, yttrium, and the lanthanides, was the discovery that the +2 oxidation state was accessible not only for Eu­(II), Yb­(II), Sm­(II), Tm­(II), Dy­(II), and Nd­(II) − but also for all the other rare-earth metals except radioactive promethium. − The new Ln­(II) ions were frequently generated in trigonal ligand environments in which a d z 2 orbital was populated to give 3d 1 (Sc), 4d 1 (Y), and 4f n 5d 1 (lanthanides) electron configurations. ,, These new Ln­(II) species are of interest not only due to their highly reducing reactivity − but also due to their physical properties. − Synthesis of complexes of the new Ln­(II) ions generally requires sub-ambient temperatures and short reaction times. Although many examples of 4f n 5d 1 Ln­(II) complexes are now known, reduction of some Ln­(III) precursors with alkali metals yields only fleeting color changes and the Ln­(II) products have evaded definitive characterization. − Therefore, it is of interest to explore alternative methods for generating Ln­(II) complexes.…”

Selective Cleavage of the Strong or Weak C–C Bonds in Biphenylene Enabled by Rare-Earth Metals

“…Similar to the reaction of 1-Sc with biphenylene, the one-pot reaction of lutetium chloride 1-Lu, biphenylene, KC 8 and 18-c-6 was conducted to provide BPDA lutetium 4b-Lu exclusively (Figure 2a). Given that the potassium ion could be encapsulated better by the threedimensional interior cavity of cryptand (crypt), 12 crypt instead of 18-c-6 was utilized in the reaction and 4c-Lu was generated. Thus, a highly selective conversion from biphenylene to benzopentalene dianion was realized by changing the rareearth center.…”