FLOW REACTORS FOR PREPARATIVE CHEMISTRY IN SUPERCRITICAL-FLUID SOLUTION - SOLVENT-FREE SYNTHESIS AND ISOLATION OF CR(CO)(5)(C2H4) AND (ETA(5)-C5H5)MN(CO)(2)(ETA(2)-H-2)

We describe the use of supercritical flow reactors as a new but relati vely straightforward approach to carrying out reaction chemistry in hi gh-pressure fluids (<350 bar). Two photochemical flow reactors are des cribed in detail, one reactor for the synthesis of Cr(CO)(5)(C2H4) fro m the reaction of Cr(CO)(6) with supercritical C2H4 (scC(2)H(4)), the other reactor for the generation of CpMn(CO)(2)(eta(2)-H-2) from CpMn( CO)(3) and H-2 in supercritical CO2 (scCO(2)). Both compounds are isol ated by rapid expansion of the supercritical solution. This is the fir st time that either compound has been isolated as a solid, and both ar e found to be not nearly as labile as had been anticipated, Indeed, Cp Mn(CO)(2)(eta(2)-H-2) is one of the simplest dihydrogen compounds so f ar to have been isolated, yet it is one of the more robust compounds, taking 2 h to react with moderately high pressures of CO or C2H4. Othe r reactions involving scC(2)H(6) as the fluid or N-2 as the reactant ( e.g., to form CpMn(CO)(2)N-2) are described briefly. So far, the react ions have been carried out on a modest scale, ca. 20-40 mg per h, but this is more a limitation of the photochemistry rather than of the rea ctors themselves. All reactions are carried out without the use of any conventional organic solvents.