New Method to Calculate the Sign and Relative Strength of Magnetic Interactions in Low-Dimensional Systems on the Basis of Structural Data

The connection of strength of magnetic interactions and type ordering the magnetic moments with crystal chemical characteristics in low-dimensional magnets is investigated. The new method to calculate the sign and relative strength of magnetic interactions in low-dimensional systems on the basis of the structural data is proposed. This method allows to estimate magnetic interactions not only inside low-dimensional fragments but also between them, and also to predict the possibility of the occurrence of magnetic phase transitions and anomalies of the magnetic interactions. Moreover, it can be used for search of low-dimensional magnets among the compounds whose crystal structures are known. The possibilities of the method are illustrated in an example of research of magnetic interactions in familiar low-dimensional magnets SrCu2(BO3)2, CaCuGe2O6, CaV4O9, Cu2Te2O5Cl2, Cu2Te2O5Br2, BaCu2Si2O7, BaCu2Ge2O7, BaCuSi2O6, LiCu2O2, and NaCu2O2.Comment: 18 pages, 8 figures, 2 tables, published versio

Water-soluble (eta(6)-arene)ruthenium(II)-phosphine complexes and their catalytic activity in the hydrogenation of bicarbonate in aqueous solution

The reactions of [(eta(6)-C6H6)RuCl2](2) and [(eta(6)-p-cymene)RuCl2](2) With hydrogen in the presence of the water-soluble phosphines tppts (meta-trisulfonated triphenylphosphine) and pta (1,3,5-triaza-7-phosphaadamantane) afforded as the main species [(eta(6)- C6H6)RuH(tppts)(2)](+), [(eta(6)-C6H6)RuH(pta)(2)](+), [(eta(6)-p-cymene)RuH(tppts)(2)](+) and [(eta(6)-p-cymene)RuH(pta)(2)](+). This latter complex was also formed in the reaction of [(eta(6)-p-cymene)RuCl2(pta)] and hydrogen with a redistribution of pta. In addition, prolonged hydrogenation at elevated temperatures and in the presence of excess of pta led to the formation of the arene-free [RuH(pta)(4)CI], [RuH(pta)(4)(H2O)](+), [RuH2(pta)(4)] and [RuH(pta)(5)](+) complexes. Ru-hydrides, such as [(eta6-arene)RuH(L)(2)](+), catalyzed the hydrogenation of bicarbonate to formate in aqueous solutions at p(H-2) = 100 bar, T = 50-70 degreesC. (C) 2004 Elsevier B.V. All rights reserved

Water-soluble analogs of [RuCl3(NO)(PPh3)(2)] and their catalytic activity in the hydrogenation of carbon dioxide and bicarbonate in aqueous solution

The new water-soluble ruthenium-nitrosyl complexes [RuCl3(NO)(TPPMS)(2)] and [RuCl3(NO)(TPPTS)(2)] were synthetized and characterized by IR, H-1 and P-31 NMR spectroscopies. The NO stretching frequencies, nu(NO) = 1870 cm(-1) (TPPMS) and 1883 cm(-1) (TPPTS) suggest a linear Ru-N-O arrangements. Reactions with OH- yield the corresponding [RuCl3 (NO2)(P)(2)] derivatives, furthermore, [RuH(NO)(P)(3)] is formed with TPPMS or TPPTS, respectively, under 100 bar H-2 pressure. The new complexes are suitable precatalysts for the hydrogenation of carbon dioxide and/or bicarbonate in aqueous solutions up to a turnover frequency of 400 h(-1) under relatively mild conditions (30 bar H-2, 70 degreesC). (C) 2003 Elsevier Science B.V. All rights reserved