Theoretical study of the rhenium-alkane interaction in transition metal-alkane σ-complexes

Metal-alkane binding energies have been calculated for [CpRe(CO)(2)](alkane) and [(CO)(2)M(C5H4)C C(C5H4)M(CO)(2)](alkane), where M = Re or Mn. Calculated binding energies were found to increase with the number of metal-alkane interaction sites. In all cases examined, the manganese-alkane binding energies were predicted to be significantly lower than those for the analogous rhenium-alkane complexes. The metal (Mn or Re)-alkane interaction was predicted to be primarily one of charge transfer, both from the alkane to the metal complex (70-80% of total charge transfer) and from the metal complex to the alkane (20-30% of the total charge transfer).