Radical-Like Activation of Alkanes by the Ligated Copper Oxide Cation (Phenanthroline)CuO⁺

Electrospray ionization mass spectrometry of copper(II) nitrate solution in the presence of phenanthroline (phen) leads to the generation of the monocation (phen)Cu(NO 3 ) + from which NO 2 is lost at elevated collision energy concomitant with formation of the ligated copper oxide cation (phen)CuO + . This structural assignment is based on the characteristic loss of atomic oxygen upon collision-induced dissociation (CID) of the mass-selected ion. In addition, loss of carbon monoxide is observed to occur upon CID, which is assigned to a transfer of the oxygen atom from the copper to the ligand to presumably afford phenanthrolinone/Cu + followed by decarbonylation. Mass-selected (phen)CuO + is found to react with alkanes larger than ethane. With propane, (phen)CuOH + and (phen)Cu + are formed as ionic products corresponding to hydrogen-atom abstraction and oxygen-atom transfer, respectively. Deuterium labeling reveals a moderate preference for the activation of secondary C−H bonds, which resemble the reactions of propane with chlorine atoms. Several minimum structures of relevant species have been optimized by density-functional calculations (B3LYP/TZVP) to obtain some thermochemical information on key intermediates along the reaction pathways. From the results, a qualitative potential-energy surface for alkane activation is suggested. With the unsaturated hydrocarbons ethene, propene, and benzene, almost exclusive oxygen-atom transfer is observed.