Evaluuation of the strength of the metal-ligand bond in manganese and rhenium carbonyl complexes with condensed π-ligands

The authors attempt to evaluate the metal-pi-ligand bond strength using mass spectral data without recourse to thermochemical data. Idenyl manganese tricarbonyl (I), idenyl rhenium tricarbonyl (II), fluorenyl manganese tricarbonyl (II), cyclopentadienyl manganese tricarbonyl (IV), and cyclopentadienyl rhenium tricarbonyl (V) were studied. It is shown that the major differences in the spectra of the manganese and rhenium complexes are related to the appearance of pronounced decomposition of the pi-ligand attached to the metal. The strength of the metal-pi-ligand bond decreases in the following order C5H5Re(CO)3; C9H7Re(CO)3; C5H5Mn(CO)3; C9H7Mn(CO)3; C13H9Mn(CO)3