Discovery and mechanistic investigation of photoinduced sp3 C–H activation of hydrocarbons by the simple anion hexachlorotitanate

The selective transformation of hydrocarbons into more chemically complex materials is an evergreen challenge in chemistry and catalysis. This report finds that the dianion hexachlorotitanate (TiCl62−) catalyzes the C–H activation of saturated hydrocarbons under 390 nm light irradiation. Investigations into the mechanism of this reaction are detailed. The photolysis event affords the formation of a chlorine radical and a mixture of TiIIICl4(NCMe)2− and TiIIICl5(NCMe)2−. The TiIIIClx species were characterized by spectrophotometry, electrochemistry, and X-ray crystallography. Alkyl radicals generated by these means were trapped by a range of alkene acceptors. Notably, the TiIIIClx species were shown to be more reducing (ΔEpa = 0.72 V) than related CeIIIClx species, enabling access to more electron-rich acceptors by facilitating the reduction of the alkyl radical trapped intermediate. Density functional theory calculations correctly identified the reactivity of alkene substrates using the CeCl62− and TiCl62− photoredox catalysts. The results herein demonstrate the impact of metal identity on C–H activation.