Transition metal formyl complex

In

The MCHO group is planar. A C=O double bond is indicated by X-ray crystallography. A second resonance structure has a M=C double bond, with negative charge on oxygen.

Synthesis and reactions

Metal formyl complexes are often prepared by the reaction of metal carbonyls with hydride reagents:^[3]

[Re(CO)₆]⁺ + H⁻ → (CO)₅ReCHO

The CO ligand is the electrophile and the hydride (provided typically from a borohydride) is the nucleophile.

Some metal formyls are produced by reaction of metal carbonyl anions with reagents that donate the equivalent of a formyl cation, such a mixed formate anhydrides.^[4]

Metal formyls participate in many reactions, many of which are motivated by interest in Fischer-Tropsch chemistry. O-alkylation gives carbenoid complexes. The formyl ligand also functions as a base, allowing the formation of M-CH=O-M' linkages.^[5] Decarbonylation leads to de-insertion of the carbonyl, yielding hydride complexes.^[2]

References