High energy photoelectron spectroscopy of transition metal complexes. Part 3.—Direct measurement and interpretation of the core level shifts between free and complexed CO, and the bonding in some substituted manganese pentacarbonyls

Abstract

The change in the core electron ionization potential of CO when complexed to first row transition metals (Cr, Mn and Fe) has been measured directly in the gas phase. For the binary carbonyls shifts of approximately 2.5 eV to lower binding energy are observed. Taking Ni(CO)4 as an example, a number of theoretical methods of calculating such shifts are investigated, but none are found to be satisfactory. Measurements of core level shifts in the molecules LMn(CO)5 are reported and discussed satisfactorily using ab initio and approximate molecular orbital calculations.