Liquid-Phase Synthesis of Highly Reactive Rare-Earth Metal Nanoparticles

The first liquid‐phase synthesis of high‐quality, small‐sized rare‐earth metal nanoparticles (1–3 nm)—ranging from lanthanum as one of the largest (187 pm) to scandium as the smallest (161 pm) rare‐earth metal—is shown. Size, oxidation state, and reactivity of the nanoparticles are examined (e.g., electron microscopy, electron spectroscopy, X‐ray absorption spectroscopy, selected reactions). Whereas the nanoparticles are highly reactive (e.g. in contact to air and water), they are chemically stable as THF suspensions and powders under inert conditions. The reactivity can be controlled to obtain inorganic and metal–organic compounds at room temperature.

Reduced Arene Complexes of Scandium

Alkali metal naphthalenide or anthracenide reacted with scandium(III) anilides [Sc(X){N(tBu)Xy}2 (thf)] (X=N(tBu)Xy (1); X=Cl (2); Xy=C6 H3 -3,5-Me2 ) to give scandium complexes [M(thf)n ][Sc{N(tBu)Xy}2 (RA)] (M=Li-K; n=1-6; RA=C10 H8 2- (3-Naph-K) and C14 H10 2- (3-Anth-M)) containing a reduced arene ligand. Single-crystal X-ray diffraction revealed the scandium(III) center bonded to the naphthalene dianion in a σ2 :π-coordination mode, whereas the anthracene dianion is symmetrically attached to the scandium(III) center in a σ2 -fashion. All compounds have been characterized by multinuclear, including 45 Sc NMR spectroscopy. Quantum chemical calculations of these intensely colored arene complexes confirm scandium to be in the oxidation state +3. The intense absorptions observed in the UV/Vis spectra are due to ligand-to-metal charge transfers. Whereas nitriles underwent C-C coupling reaction with the reduced arene ligand, the reaction with one equivalent of [NEt3 H][BPh4 ] led to the mono-protonation of the reduced arene ligand.

Samarium Polyarsenides Derived from Nanoscale Arsenic

Zintl phases of arsenic and molecular compounds containing Zintl-type polyarsenide ions are of fundamental interest in basic and applied sciences. Unfortunately, the most obvious and reactive arsenic source for the preparation of defined molecular polyarsenide compounds, yellow arsenic As₄ , is very inconvenient to prepare and neither storable in pure form nor easy to handle. Herein, we present the synthesis and reactivity of elemental As⁰ nanoparticles (As⁰ _Nano , d=7.2±1.8 nm), which were successfully utilized as a reactive arsenic source in reductive f-element chemistry. Starting from [Cp*₂ Sm] (Cp*=η⁵ -C₅ Me₅ ), the samarium polyarsenide complexes [(Cp*₂ Sm)₂ (μ-η² :η² -As₂ )] and [(Cp*₂ Sm)₄ As₈ ] were obtained from As⁰ _nano , thereby generating the largest molecular polyarsenide of the f-elements and circumventing the use of As₄ in preparative chemistry.

Samarium Polystibides Derived from Highly Activated Nanoscale Antimony

Zintl ions in molecular compounds are of fundamental interest for basic research and application. Two reactive antimony sources are presented that allow direct access to molecular polystibide compounds. These are Sb amalgam (Sb/Hg) and ultrasmall Sb⁰ nanoparticles (d=6.6±0.8 nm), which were used independently as precursors for the synthesis of the largest f-element polystibide, [(Cp*₂ Sm)₄ Sb₈ ]. Whereas the reaction of the nanoparticles with [Cp*₂ Sm] directly led to [(Cp*₂ Sm)₄ Sb₈ ], Sm/Sb/Hg intermediates were isolated when using Sb/Hg as the precursor. These Sm/Sb/Hg intermediates [{(Cp*₂ Sm)₂ Sb}₂ (μ-Hg)] and [{(Cp*₂ Sm)₃ (μ⁴ ,η^1:2:2:2 -Sb₄ )}₂ Hg] were synthetically trapped and structurally characterized, giving insight in the formation mechanism of polystibide compounds.