PREPARATION OF ORGANIC SOLUTIONS OR SOLID FILMS OF SMALL PARTICLES OF RUTHENIUM, PALLADIUM, AND PLATINUM FROM ORGANOMETALLIC PRECURSORS IN THE PRESENCE OF CELLULOSE DERIVATIVES

Reaction of Ru(cod)(cot) with hydrogen in the presence of nitrocellulose (NC) or cellulose acetate (CA) at 20-degrees-C yields colloidal ruthenium solutions containing particles of 10, 15, and 20 angstrom, respectively, and showing a low dispersity for concentrations in Ru of 2, 5, and 10 wt % (NC) or particles of average size 15, 20, and 25 angstrom for concentrations in Ru of 2, 5, and 10 wt % (CA). No change in particle size is observed upon reaction with CO in NC whereas agglomeration occurs in CA. The infrared spectra of CO adsorbed on Ru colloids have been recorded. Whatever the stabilizing polymer, two bands were observed. A band at 2030 cm-1 has been assigned to the stretching vibration of CO linearly adsorbed on the Ru surface. A low-frequency band at 1965 cm-1 has been assigned to bridging CO. The relative intensities of these two bands were found to vary with particle size. Reaction of M(dba)2 (M = Pd, Pt; dba = dibenzylidene acetone) under CO in the presence of NC or AC leads to colloidal solutions containing small metal particles (respectively 35 angstrom for Pd in NC or CA, 12 angstrom for Pt in NC, 15 angstrom for Pt in CA independent of metal/polymer concentration). The presence of coordinated CO was observed in all cases. At maximum coverage, palladium colloids showed 3-fold and 2-fold bridging CO respectively at 1950 and 1890 cm-1; platinum colloids showed both bridging and terminal CO at 1880 and 2050 cm-1.