''Solvent-free'' photochemical activation of CH4, C2H4, and C2H6 by (C(5)Me(5))Ir(CO)(2) in supercritical fluid solution

We report the activation of H-2 and light hydrocarbons (CH4, C2H4, and C2H6) by Cp*Ir(CO)(2) (Cp* = eta(5)-C(5)Me(5)) in supercritical fluid solution. The reactions have been carried out both in the presence of a supercritical solvent (scCO(2), scXe, or scCHF(3)) or ''solvent-free'' in the pure supercritical hydrocarbon (scCH(4), scC(2)H(4), or scC(2)H(6)). As far as We are aware, this is the first use of scCH(4) as a solvent for photochemical reactions. The presence of H-2 in scC(2)H(6) greatly enhances the effectiveness of the C-H activation, but even in the presence of D-2, Cp*Ir(CO)(H)Et and not Cp*Ir(CO)(D)Et is formed. Reaction of Cp*Ir(CO)(2) with H-2 occurs efficiently in CHF3, but C-H activation of C2H6 is almost suppressed in this mixed scC(2)H(6)/ scCHF(3) fluid, possibly through H-bonding to the metal center. A technique for recovering the products from milligram-scale reactions is described.