Photochemistry of tris(diethyldithiocarbamato)iron(III). Reduction to a stable iron(II) complex induced by ligand-to-metal charge transfer excitation

The photolysis of FeIII(et2dtc)3 with et2dtc− = diethyldithiocarbamate in inert solvents (e.g., CH3CN) and in the presence of 1,2-bis(diphenylphosphino)ethane (dppe) leads to the formation of FeII(et2dtc)2(dppe) and (et2dtc)2 = tetraethylthiuramdisulfide. At equimolar concentrations (2.76×10−5 M) of FeIII(et2dtc)3 and dppe the quantum yields are φ=0.007 at λirr=333 nm and 0.003 at 436 nm. This photoreaction, which is initiated by ligand-to-metal charge transfer excitation, generates FeII(et2dtc)2 and a et2dtc radical in the primary photochemical step. Product formation occurs by the interception of FeII(et2dtc)2 with dppe.