THF solutions of the new organometallic precursor Co(η 3 -C 8 H 13 )(η 4 -C 8 H 12 ) react with 3 bar dihydrogen in the presence of polyvinylpyrrolidone (PVP) at three different temperatures, namely, 0, 20, and 60 °C to give colloidal solutions containing fcc cobalt particles of respectively e1 nm (Coll. 1) and ca. 1.5 nm (Coll. 2 and Coll. 3) mean sizes, as evidenced by HREM analysis. All colloids react with carbon monoxide to give new colloids (Coll. 1′-3′) displaying broad CO stretches near 2000 and 1890 cm -1 on their infrared spectra recorded in KBr disks. The magnetic behavior of the colloids was studied by SQUID techniques. Coll. 1-3 display a typical superparamagnetic behavior with blocking temperatures in the range 9-10 K. From magnetization studies above and below the blocking temperature, it was possible to determine that Coll. 3 shows a mean size of 1.6 nm and a very narrow size distribution. Because of a magnetic surface effect, the magnetic moment per atom (µ Co ) 1.94 ( 0.04 µ B ) appears significantly larger than the value admitted for bulk cobalt. In contrast, Coll. 2′ shows a weak magnetization and disappearance of the blocking temperature as a result of CO coordination.

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A Ni 0 (15 wt %)/Al 2 O 3 catalyst is prepared by impregnation using [Ni(en) 2 (H 2 O) 2 ](NO 3 ) 2 as precursor salt containing the chelating ligand ethylenediamine (en). Due to the low solubility of this salt and the high viscosity of its solution, large crystals of the salt deposit on the support, clogging the porosity of alumina. These crystals split during the thermal treatment in argon; hydrogen produced in situ from organic residues reduces quantitatively nickel (II) to monodisperse small Ni 0 particles, compared with only one half of nickel reduced by hydrogen when catalysts are prepared from [Ni(H 2 O) 6 ](NO 3 ) 2 . To cite this article:

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Sonolysis of a solution of Fe(CO) 5 in anisol in the presence of poly(dimethylphenylene oxide) (PPO) leads to the formation of small nonagglomerated iron particles. HREM analysis shows that the size of the particles is centered around 30 Å with a medium dispersity. HREM analysis of the particles demonstrate that the smaller particles (e25 Å) adopt the R-Fe (bcc) structure, whereas the larger ones (g25 Å) adopt the γ-Fe (fcc) structure. Magnetic measurements confirm the presence of small superparamagnetic particles (R-Fe) and of mostly antiferromagnetic or paramagnetic particles (γ-Fe).

Films and monoliths containing the spin crossover complex [Fe(Htrz)(2)(trz)](BF(4)) (trz = 1,2,4-triazole) as nanoparticles have been obtained. The dispersion and consecutive inclusion of the Fe complex in a silica matrix prepared from tetramethoxysilane or tetraethoxysilane afford monoliths or films with a violet colour at room temperature, which turns white above 380 K. This change of colour is reversible. This thermochromic behaviour has been characterized by measuring the magnetic properties together with thermogravimetric studies and Raman spectroscopy, the result of which all demonstrate that both films and monoliths undergo a spin crossover. Microscopy studies confirm the occurrence of the Fe complex as nanoparticles, in both the monoliths and the films. The facile synthesis of these materials as nanoparticles in transparent films should open the possibility of the synthesis of high quality films.

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Although molecular metals have been known for decades, their insolubility, low vapor pressure, and synthesis routes have prevented them from being integrated into electronic devices. We have prepared stable colloidal solutions of the organic metal TTF-TCNQ that overcome such difficulties. The solutions contain well-dispersed nanoparticles stabilized by long alkyl chain amines. They afford soluble powders by evaporation and homogeneous thin films by drop-casting. Powders and films show room temperature conductivities in the 0.01-0.1 S cm(-1) range.