Igor L. Fedushkin

Atomic-layer deposition of Lu2O3

Rare earth oxides could represent a valuable alternative to SiO2 in complementary metal–oxide–semiconductor devices. Lu2O3 is proposed because of its predicted thermodynamical stability on silicon and large conduction band offset. We report on the growth by atomic-layer deposition of lutetium oxide films using the dimeric {[C5H4(SiMe3)]2LuCl}2 complex, which has been synthesized for this purpose, and H2O. The films were found to be stoichiometric, with Lu2O3 composition, and amorphous. Annealing in nitrogen at 950°C leads to crystallization in the cubic bixbyite structure. The dielectric constant of the as-grown Lu2O3 layers is 12±1.

Fabrication of GeO2 layers using a divalent Ge precursor

Good quality and perfectly stoichiometric GeO2 layers are promising interlayers to be implemented in alternative devices based on high dielectric constant oxide/Ge(100). In this work, the authors report on the growth by atomic layer deposition of GeO2 films using a divalent Ge precursor combined with O3. The films are composed of smooth and perfectly stoichiometric GeO2. The contamination level is extremely low. The deposited GeO2 films have a band gap of 5.81±0.04eV. The conduction and valence band offsets at the GeO2∕Ge heterojunction are found to be 0.6±0.1 and 4.5±0.1eV, respectively.

[NdI2(thf)5], the First Crystallographically Authenticated Neodymium(II) Complex

Two new starting materials for a new chemistry of low-valent lanthanide compounds are the first crystallographically characterized molecular complexes of the rare Nd2+ ion, [NdI2 (thf)5 ] (1), and [TmI2 (thf)(dme)2 ] (2; dme=1,2-dimethoxyethane). These have a pentagonal-bipyramidal structure in which the two iodine atoms are in axial positions.

Reversible Addition of Alkynes to Gallium Complex of Chelating Diamide Ligand

Different alkynes add reversibly to the gallium complex of the dpp-Bian dianion. The reactions proceed with addition of the alkynes across the Ga-N-C fragment resulting in carbon-carbon and carbon-gallium bonds. In the case of 3 and 4 a full elimination of the alkyne takes place at T < 100 degrees C, whereas with adducts 5 and 6 it occurs at heating to ca. 200 degrees C.

Dialane with a Redox-Active Bis-amido Ligand: Unique Reactivity towards Alkynes

The treatment of 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene (dpp-bian) with one equivalent of AlCl(3) and three equivalents of sodium in toluene at 110 °C produced a stable dialane, (dpp-bian)Al-Al(dpp-bian) (1). The reaction of compound 1 with pyridine gave Lewis-acid-base adduct (dpp-bian)(Py)Al-Al(Py)(dpp-bian) (2). Acetylene and phenylacetylene reacted with compound 1 to give cycloaddition products [dpp-bian(R(1)R(2))]Al-Al[(R(2)R(1))dpp-bian] (3: R(1)=R(2)=CH; 4: R(1)=CH, R(2)=CPh). These addition reactions occur across Al-N-C moieties and result in the formation of new C-C and C-Al bonds. At elevated temperatures, compound 4 rearranges into complex 5, which consists of a radical-anionic dpp-bian ligand and two bridging alken-1,2-diyl moieties, (dpp-bian)Al(HCCPh)(2)Al(dpp-bian). This transformation is accompanied by cleavage of the dpp-bian-ligand-alkyne C-C bond, as well as of the Al-Al bond. In contrast to its analogous gallium complex, compound 1 is reactive towards internal alkynes. In the reaction of compound 1 with PhC≡CMe, besides symmetrical addition product [dpp-bian(R(1)R(2))]Al-Al[(R(2)R(1))dpp-bian] (R(1)=CMe, R(2)=CPh; 6), monoadduct [dpp-bian(R(1)R(2))]Al-Al(dpp-bian) (R(1)=CMe, R(2)=CPh; 7) was also isolated. Complexes 1-7 were characterized by IR, (1)H NMR (1-4), and electronic absorption spectroscopy (3-5); the molecular structures of compounds 1-7 were determined by single-crystal X-ray diffraction.

Addition of Alkynes to a Gallium Bis‐Amido Complex: Imitation of Transition‐Metal‐Based Catalytic Systems

Acetylene, phenylacetylene, and alkylbutynoates add reversibly to (dpp-bian)Ga-Ga(dpp-bian) (dpp-bian=1,2-bis[(2,6-diisopropylphenyl)-imino]acenaphthene) to give addition products [dpp-bian(R(1)C=CR(2))]Ga-Ga[(R(2)C=CR(1))dpp-bian]. The alkyne adds across the Ga-N-C section, which results in new carbon-carbon and carbon-gallium bonds. The adducts were characterized by electron absorption, IR, and (1)H NMR spectroscopy and their molecular structures have been determined by single-crystal X-ray analysis. According to the X-ray data, a change in the coordination number of gallium from three [in (dpp-bian)Ga-Ga(dpp-bian)] to four (in the adducts) results in elongation of the metal-metal bond by approximately 0.13 Å. The adducts undergo a facile alkynes elimination at elevated temperatures. The equilibrium between [dpp-bian(PhC=CH)]Ga-Ga[(HC=CPh)dpp-bian] and [(dpp-bian)Ga-Ga(dpp-bian) + 2 PhC≡CH] in toluene solution was studied by (1)H NMR spectroscopy. The equilibrium constants at various temperatures (298≤T≤323 K) were determined, from which the thermodynamic parameters for the phenylacetylene elimination were calculated (ΔG°=2.4 kJ mol(-1), ΔH°=46.0 kJ mol(-1), ΔS°=146.0 J K(-1) mol(-1)). The reactivity of (dpp-bian)Ga-Ga(dpp-bian) towards alkynes permits use as a catalyst for carbon-nitrogen and carbon-carbon bond-forming reactions. The bisgallium complex was found to be a highly effective catalyst for the hydroamination of phenylacetylene with anilines. For instance, with [(dpp-bian)Ga-Ga(dpp-bian)] (2 mol%) in benzene more than 99% conversion of PhNH(2) and PhC≡CH into PhN=C(Ph)CH(3) was achieved in 16 h at 90 °C. Under similar conditions, the reaction of 1-aminoanthracene with PhC≡CH catalyzed by (dpp-bian)Ga-Ga(dpp-bian) formed a carbon-carbon bond to afford 1-amino-2-(1-phenylvinyl)anthracene in 99% yield.

Genuine Redox Isomerism in a Rare‐Earth‐Metal Complex

Redox isomerism is observed for a lanthanide complex for the first time. Upon lowering the temperature, an electron of [{(dpp-bian)Yb(μ-Cl)(dme)}(2)] (1) is transferred from the metal to the ligand (see picture), giving rise to marked shortening of Yb-N bonds and a hysteretic jump in the magnetic moment. The crystal packing is of a crucial importance, as two other crystal modifications of 1 do not undergo this effect.

Redox Isomerism in the Lanthanide Complex [(dpp-Bian)Yb(DME)(μ-Br)]2 (dpp-Bian = 1,2-Bis[(2,6-diisopropylphenyl)imino]acenaphthene)†

Ytterbium reacts with 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene (1, dpp-Bian) in 1,2-dimethoxyethane (DME) to give complex (dpp-Bian)Yb(DME)(2) (2). Oxidation of 2 with an 0.5 mol equivalent of dibromostilbene affords dimeric compound [(dpp-Bian)Yb(DME)(mu-Br)](2) (3). Molecular structures of 2 and 3 were determined by single-crystal X-ray analysis. In complex 3 in a DME solution, a temperature-dependent reversible intramolecular electron transfer between the ligand and the metal takes place.

Binuclear complexes of La(III) and Eu(II) with the bridging naphthalene dianion. Synthesis and X-ray crystallographic analysis of [μ2-η4:η4-C10H8][LaI2(THF)3]2 and [μ2-η4:η4-C10H8][EuI(DME)2]2

Abstract The treatment of LaI 3 (THF) 3 with equimolar amounts of Li and excess of C 10 H 8 in THF results in the formation of [C 10 H 8 ][LaI 2 (THF) 3 ] 2 ( 1 ) and the reaction of EuI 2 (THF) 2 with Li and C 10 H 8 in DME leads to [C 10 H 8 ][EuI(DME) 2 ] 2 ( 2 ), which have been characterized by IR and UV-VIS spectroscopy as well as by X-ray crystallography. 1 is monoclinic, space group P 2 1 / c (No. 14), Z = 4, with a = 1314.2(6), b = 1256.7(5), c = 1697.2(4) pm, β = 93.53(3)°. The structure was refined to R = 0.045 for 2377 observed reflections( F 0 > 4 σ ( F 0 )). 2 is monoclinic, space group P 2 1 / n , Z = 4 with a = 1015.1(3), b = 1389.8(4), c = 1269.8(3) pm, β = 97.51(2)°. The structure was refined to R = 0.0408 for 2687 observed reflections ( F 0 > 4 σ ( F 0 )). Both molecules contain two LaI 2 (THF) ( 1 ) or EuI(DME) moieties ( 2 ), bridged η 4 each by a non planar naphthalene with dihedral angles of 15° ( 1 ) and 6° ( 2 ) respectively.

A Chemical Definition of the Effective Reducing Power of Thulium(II) Diiodide by Its Reactions with Cyclic Unsaturated Hydrocarbons

Thulium diiodide reduces cyclic aromatic hydrocarbons that have reduction potentials more positive than - 2.0 V versus SCE. Thus, TmI2 reacts with cyclooctatetraene or acenaphthylene in THF, or with lithium anthracenide in 1,2-dimethoxyethane (DME) to give thulium triiodide and the thulium(III) complexes [(eta8-C8H8)TmI(thf)2] (1), rac-ansa-[(eta5-C12H8)2TmI(thf)] (2), or [(eta2-C14H10)TmI-(dme)2] (3), respectively. The molecular structures of 1-3 were determined by single-crystal X-ray diffraction.