Photochemistry of [Cu{HB(3,5-Me2pz)3}]2X (X=O2−, CO32−) in non-aqueous solvents

The photochemistry and thermal stability of [Cu(HB(3,5-Me2pz)3)]2O (1) and [Cu(HB(3,5-Me2pz)3)]2CO3 (2) have been investigated in various solvents in view of their utilisation as catalysts in olefin functionalization reactions. Irradiation of the above complexes in chlorinated aliphatic solvents within the CT-band region generates the mononuclear complex [Cu(HB(3,5-Me2pz)3)Cl] (4), which exists as a tetracoordinated monomer in solution at room temperature, and as a dimer (pentacoordinated-Cu(II) species, 4″) in a frozen solution or in the solid state. In coordinating solvents 4 is converted into the monomer pentacoordinated complex [Cu(HB(3,5-Me2pz)3)Cl(Solv)] (4′). The photo-generation of 4 implies the homolytic cleavage of the Cu–O bond in 1, with formation of the reactive radical species [LCu(I)] and [LCu(II) O . ] [L = (HB(3,5-Me2pz)3)]. 2 appears to be more stable than 1, under the same conditions. The radical Cu(II)-species [LCu(II) O . ], according to the solvent and conditions, can either be reduced to [LCu(I)], or undergo an intramolecular rearrangement.