The reproducible production of fine particles of three neutral metal carbonyls-chromium hexacarbonyl, dimanganese decacarbonyl, and triiron dodecacarbonyl-has been demonstrated using the rapid expansion of supercritical solutions (RESS) process. Particles produced by the RESS process were generally smaller and more uniform than the starting material, as observed by optical microscopy. Chromium hexacarbonyl was extracted with supercritical carbon dioxide at 100 bar and 80 degrees C, and was deposited as fine particles by expansion through a nozzle into a sealed vessel (atomizer) pressurized at 25 bar. These conditions were also used for dimanganese decacarbonyl, but the pressure in the atomizer was 10 bar. For triiron dodecacarbonyl, the conditions used for chromium hexacarbonyl were applied, but the extraction pressure was 200 bar. Some decomposition of the carbonyls in the extraction cell occurred. No fine particles of two chiral complexes, [R(+)-2,2'-bis(diphenylphosphino)-1,1'-binaphthalene]chloro(p-cymene)ruthenium chloride and [R(+)-2,2'-bis(diphenylphosphino)-1,1'-binaphthalene]ruthenium [beta-bis(eta(2)-propanoate)], could be produced by RESS with supercritical carbon dioxide.