In this work a simple concept was used for a systematic search for new materials with high spin polarization. It is based on two semi-empirical models. Firstly, the Slater-Pauling rule was used for estimation of the magnetic moment. This model is well supported by electronic structure calculations. The second model was found particularly for Co2 based Heusler compounds when comparing their magnetic properties. It turned out that these compounds exhibit seemingly a linear dependence of the Curie temperature as function of the magnetic moment.Stimulated by these models, Co2FeSi was revisited. The compound was investigated in detail concerning its geometrical and magnetic structure by means of X-ray diffraction, X-ray absorption and Mößbauer spectroscopies as well as high and low temperature magnetometry. The measurements revealed that it is, currently, the material with the highest magnetic moment (6µB ) and Curietemperature (1100K) in the classes of Heusler compounds as well as half-metallic ferromagnets. The experimental findings are supported by detailed electronic structure calculations.

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The controlled decomposition of Pt2(dba)3 (dba = dibenzylideneacetone) dispersed in 1-n-butyl-3-methylimidazolium tetrafluoroborate (BMI.BF4) and hexafluorophosphate (BMI.PF6) ionic liquids in the presence of cyclohexene by molecular hydrogen produces Pt0 nanoparticles. The formation of these nanoparticles follows the two-step [A --> B, A + B --> 2B (k1, k2)] autocatalytic mechanism. The catalytic activity in the hydrogenation of cyclohexene is influenced by the nature of the anion rather than the mean-diameter of the nanoparticles. Thus, higher catalytic activity was obtained with Pt0 dispersed in BMI.BF4 containing the less coordinating anion although these nanoparticles possess a larger mean diameter (3.4 nm) than those obtained in BMI.PF6 (2.3 nm). Similar mean diameter values were estimated from in situ XRD and SAXS. XPS analyses clearly show the interactions of the ionic liquid with the metal surface demonstrating the formation of an ionic liquid protective layer surrounding the platinum nanoparticles. SAXS analysis indicated the formation of a semi-organized ionic liquid layer surrounding the metal particles with an extended molecular length of around 2.8 nm in BMI.BF4 and 3.3 nm in BMI.PF6.

The diameter and size-distribution of Ni nanoparticles prepared by the decomposition of [bis(1,5-cyclooctadiene)nickel(0)] organometallic precursor dissolved in 1-alkyl-3-methylimidazolium N-bis(trifluoromethanesulfonyl) amide ionic liquids depend on the length of the alkyl side-chain of the imidazolium ring. The increase of the organization range order of the ionic liquid that increases with that of the alkyl side-chain (from n-butyl to n-hexadecyl) induces the formation of nanoparticles with a smaller diameter and size-distribution. The cubic fcc Ni nanoparticles with 4.9 +/- 0.9 to 5.9 +/- 1.4 nm in mean diameter and monomodal size-distribution thus prepared are probably composed of a small cap layer of NiO around a core of Ni metal. The contribution of the oxide layer also depends on the medium i.e. the metal oxide ratio increases in salts containing four to eight carbons on their side-chains and then decreases as the number of carbons increases. The Ni nanoparticles dispersed in the ionic liquids are active catalysts for the hydrogenation of olefins under relatively mild reaction conditions.

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The controlled decomposition of an Ru(0) organometallic precursor dispersed in 1-n-butyl-3-methylimidazolium hexafluorophosphate (BMI.PF(6)), tetrafluoroborate (BMI.BF(4)) or trifluoromethane sulfonate (BMI.CF(3)SO(3)) ionic liquids with H(2) represents a simple and efficient method for the generation of Ru(0) nanoparticles. TEM analysis of these nanoparticles shows the formation of superstructures with diameters of approximately 57 nm that contain dispersed Ru(0) nanoparticles with diameters of 2.6+/-0.4 nm. These nanoparticles dispersed in the ionic liquids are efficient multiphase catalysts for the hydrogenation of alkenes and benzene under mild reaction conditions (4 atm, 75 degrees C). The ternary diagram (benzene/cyclohexene/BMI.PF(6)) indicated a maximum of 1 % cyclohexene concentration in BMI.PF(6), which is attained with 4 % benzene in the ionic phase. This solubility difference in the ionic liquid can be used for the extraction of cyclohexene during benzene hydrogenation by Ru catalysts suspended in BMI.PF(6). Selectivities of up to 39 % in cyclohexene can be attained at very low benzene conversion. Although the maximum yield of 2 % in cyclohexene is too low for technical applications, it represents a rare example of partial hydrogenation of benzene by soluble transition-metal nanoparticles.

The reduction of Pd(acac) 2 (acac ¼ acetylacetonate), dissolved in 1-n-butyl-3-methylimidazolium hexafluorophosphate (BMI · PF 6 ) or tetrafluoroborate (BMI · BF 4 ) ionic liquids, by molecular hydrogen (4 atm) at 75 8C affords stable, nanoscale Pd(0) particles with sizes of 4.9 AE 0.8 nm. Inasmuch as 1,3-butadiene is at least four times more soluble in the BMI · BF 4 than butenes, the selective partial hydrogenation could be performed by Pd(0) nanoparticles embedded in the ionic liquid. Thus, the isolated nanoparticles promote the hydrogenation of 1,3-butadiene to butenes under solventless or multiphase conditions. Selectivities up to 97% in butenes were observed in the hydrogenation of 1,3-butadiene by Pd(0) nanoparticles embedded in BMI · BF 4 under mild reaction conditions (40 8C and 4 atm of hydrogen at constant pressure). Selectivities up to 72% in 1-butene were achieved at 99% 1,3-butadiene conversion, 40 8C and 4 atm of constant pressure of hydrogen. The amounts of butane (fully hydrogenated 1,3-butadiene) and cis-2-butene products are marginal and the butenes do not undergo isomerisation process, indicating that the soluble Pd(0) nanoparticles possess a pronounced surface-like rather than homogeneouslike catalytic properties.

Stable Pd(0) and Rh(0) nanoparticles with small and narrow size distribution can be prepared from relative large and agglomerated transition-metal particles dispersed in 1-n-butyl-3methylimidazolium hexafluorophosphate ionic liquid by simple laser irradiation. The laser irradiation is a complementary method for the generation of stable metal colloids in ionic liquids and also for the regeneration of small-size nanoparticles that may result from their agglomeration after different applications.