Transition-metal organometallic chemistry
Figure 197
CO complexes
1.σ *→dσ
2.dπ→π *
These interactions are synergicin increading the M-CO bond strength. In fact, the second
interaction, as known aspi backbondingincreases the available electron density on the CO.
The partial filling of the π* orbital leads to a weakened C-O triple bond, as showed from
the stretching frequencies (in cm-1) of CO free and in M/CO complexes.
free CO 2143
V(CO) 6 1976
Ni(CO) 4 2057
Cr(CO) 6 2000
Arene complexes
Carbenes and carbynes compounds
Fischer carbenes
By treatment of a CO complex with a strongnucleophile
Figure 198