О методике оценки критических определителей в рамках вопроса оценки константы совместных диофантовых приближений

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Оценка константы наилучших совместных диофантовых приближений для n = 5 и n = 6

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Lanthanide(II) Complexes Supported by N,O-Donor Tripodal Ligands: Synthesis, Structure, and Ligand-Dependent Redox Behavior

The preparation and characterization of a series of complexes of the Yb and Eu cations in the oxidation state II and III with the tetradentate N,O-donor tripodal ligands (tris(2-pyridylmethyl)amine (TPA), BPA(-) (HBPA=bis(2-pyridylmethyl)(2-hydroxybenzyl)amine), BPPA(-) (HBPPA=bis(2-pyridylmethyl)(3.5-di-tert-butyl-2-hydroxybenzyl)amine), and MPA(2-) (H(2)MPA=(2-pyridylmethyl)bis(3.5-di-tert-butyl-2-hydroxybenzyl)amine) is reported. The X-ray crystal structures of the heteroleptic Ln(2+) complexes [Ln(TPA)I-2] (Ln=Eu, Yb) and [Yb(BPA)I(CH3CN)](2), of the Ln(2+) homoleptic [Ln(TPA)(2)]I-2 (Ln=Sm, Eu, Yb) and [Eu(BPA)(2)] complexes, and of the Ln(3+) [Eu(BPPA)(2)]OTf and [Yb(MPA)(2)K(dme)(2)] (dme=dimethoxyethane) complexes have been determined. Cyclic voltammetry studies carried out on the bis-ligand complexes of Eu3+ and Yb3+ show that the metal center reduction occurs at significantly lower potentials for the BPA(-) ligand as compared with the TPA ligand. This suggests that the more electron-rich character of the BPA(-) ligand results in a higher reducing character of the lanthanide complexes of BPA(-) compared with those of TPA. The important differences in the stability and reactivity of the investigated complexes are probably due to the observed difference in redox potential. Preliminary reactivity studies show that whereas the bis-TPA complexes of Eu2+ and Yb2+ do not show any reactivity with heteroallenes, the [Eu(BPA)(2)] complex reduces CS2 to afford the first example of a lanthanide trithiocarbonate complex

Highly Active, Chemo- and Regioselective Yb II and Sm II Catalysts for the Hydrophosphination of Styrene with Phenylphosphine

International audienceStable heteroleptic amido YbII and SmII complexes bearing aminoether–phenolate ligands and devoid of coordinated solvent have been structurally characterized. They afford highly active, chemoselective and, in the case of monoadditions, 100% anti-Markovnikov regiospecific catalysts (down to 0.04 mol% loading) for the hydrophosphination of styrene with PhPH2 under mild conditions