METAL TO LIGAND CHARGE-TRANSFER PHOTOCHEMISTRY OF METAL METAL-BONDED COMPLEXES .10. PHOTOCHEMICAL AND ELECTROCHEMICAL STUDY OF THE ELECTRON-TRANSFER REACTIONS OF MN(CO)3(ALPHA-DIIMINE)(L). (L = N-DONOR, P-DONOR) RADICALS FORMED BY IRRADIATION OF (CO)5MNMN(CO)3(ALPHA-DIIMINE) COMPLEXES IN THE PRESENCE OF L

This article describes the catalytic properties of Mn(CO)3(alpha-diimine)(L).radicals, formed by irradiation with visible light of the complexes (CO)5MnMn(CO)3(alpha-diimine) (1) in the presence of L (L = N-, P-donor). The radicals initiate the catalytic disproportionation of complexes 1 in an electron transfer chain (ETC) reaction to give Mn(CO)5- and [Mn(CO)3(alpha-diimine)(L)]+. The efficiency of this reaction is low if L is a hard base; it increases for ligands having smaller cone angles and, for phosphines, higher basicities. The Mn(CO)3(alpha-diimine)(L). radicals also reduce several of the cluster compounds M3(CO)12-x(PR3)x (M = Fe, Ru; x = 0-2) and catalyze the substitution of CO by PR3. In that case the efficiency of the reaction is mainly determined by the reduction potentials of the [Mn(CO)3(alpha-diimine)(PR3)]+ cation and the cluster. These potentials have been measured with cyclic voltammetry and differential pulse voltammetry.