Paramagnetic transition-metal carbonyls and cyanides. Part 7. Electron addition to pentacarbonyl halides of chromium, molybdenum, tungsten, and rhenium induced by ionizing radiation. An electron spin resonance study

Abstract

Exposure of tetra-alkylammonium salts of [Cr(CO)₅I]^–, [Mo(CO)₅I]^–, and [W(CO)₅I]^–, and dilute solutions of [Re(CO)₅Br] and [Re(CO)₅I] in methyltetrahydrofuran (mthf), to ^6OCo γ-rays at 77 K gave electron-addition products characterized by large hyperfine coupling to the halogen and metal nuclei. Orbital populations for the extra electrons estimated therefrom showed trends characteristic of antibonding electrons, and in all cases the extra electron appears to be accommodated in the metal–halogen σ* orbital comprising primarily (d_z²–p_z). For the tungsten complex, a species exhibiting additional hyperfine coupling to a single proton was also detected. A species previously assigned the formula [Cr(CO)₅I] was prepared, but gave no detectable e.s.r. spectrum.