Preparation of colloidal dispersions of ruthenium, rhodium, osmium and iridium by the polymer-catalyzed decomposition of carbonyl cluster compounds thereof

A method for the preparation of a homogeneous, physically stable colloidal elemental dispersion of a transition metal selected from the group consisting of ruthenium, rhodium, osmium and iridium comprising:

• (a) preparing a solution in an inert solvent of a functional polymer, the concentration of the polymer being below its critical entanglement concentration, to provide discrete reactive binding sites to which transition metal cluster compound molecules can become bound;
• (b) incrementally adding, at suitable time intervals, a labile transition metal cluster compound, the molecules of which rapidly become bound to the reactive sites of the polymer;
• (c) maintaining a temperature which is sufficiently high to decompose the polymer-bound transition metal cluster compound much more rapidly than any transition metal cluster compound which may remain unbound in the solution decomposes to metal;
• (d) continuing the addition of increments of transition metal cluster compound to yield colloidal transition metal particles of the desired size within the range of from about 10 Angstrom units to about 200 Angstrom units, the transition metal particles being bound to the polymer molecules;
• and
• (e) steps (b), (c) and (d) being carried out in an inert atmosphere.