Organic Chemistry

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