Consequences of the Formation of an Organometallic Exciplex [Hg(η2-arene)] in Mercury-Photosensitized Reactions of Arenes:  C−C, C−O, and C−N Bond Cleavage

We have previously shown that mercury-photosensitized reactions give an unexpected C−C bond cleavage for PhCH2−CH3 and related aromatic systems. In this paper we report further theoretical and experimental studies that demonstrate the importance of organometallic intermediates of the type 3[Hg(η2-ArR)] in this chemistry and suggest how the C−C cleavage reaction occurs. We also find that in addition to these C−C bond cleavage reactions, analogous C−O and C−N bond cleavages can also occur with the following preference order for bond cleavage: C−O > C−N > C−C.