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We report the activation of H2 and light hydrocarbons (CH4, C2H4, and C2H6) by Cp*Ir(CO)2 (Cp* = η5-C5Me5) in supercritical fluid solution. The reactions have been carried out both in the presence of a supercritical solvent (scCO2, scXe, or scCHF3) or “solvent-free” in the pure supercritical hydrocarbon (scCH4, scC2H4, or scC2H6). As far as we are aware, this is the first use of scCH4 as a solvent for photochemical reactions. The presence of H2 in scC2H6 greatly enhances the effectiveness of the C−H activation, but even in the presence of D2, Cp*Ir(CO)(H)Et and not Cp*Ir(CO)(D)Et is formed. Reaction of Cp*Ir(CO)2 with H2 occurs efficiently in CHF3, but C−H activation of C2H6 is almost suppressed in this mixed scC2H6/scCHF3 fluid, possibly through H-bonding to the metal center. A technique for recovering the products from milligram-scale reactions is described.

A miniature flow reactor has been developed for photochemical reactions in supercritical fluids; [Cr(CO)5(C2H4)] is isolated, for the first time, by the UV photolysis of [Cr(CO)61 in supercritical C2H4 a t room temp. with a yield of ca. 40 m g per hour at ca. 80% purity as estimated by IR spectroscopy.

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