Electron addition to [Mn2(CO)10] and [Mn2(CO)8(PR3)2] induced by ionizing radiation: an electron spin resonance study

Abstract

Exposure of dilute solutions of the title compounds to ⁶⁰Co γ-rays at 77 K gave the corresponding anions. Analyses of the e.s.r. spectra show that the excess electron is accommodated in the metal–metal σ* orbital. A small extra splitting for two equivalent ³¹P nuclei for the [Mn₂(CO)₈(PR₃)₂]˙^– anion shows that delocalisation of electron density onto the axial ligands is small (ca. 1%). This unexpectedly low value may account for the absence of any ¹³C splitting for the anion derived from [Mn₂(CO)₁₀] enriched with ¹³C in the axial ligands. These results are compared with those for the cobalt anion, [Co₂(CO)₆(PR₃)₂]˙^–, which has been reported elsewhere to have a far higher spin density on the phosphine ligands (ca. 23%).