This chapter discusses the synthesis of transition-metal formyl complexes, their physical properties, their reactions, and topics relating to the stability and decomposition of transition-metal formyl complexes. The synthesis, chemical characterization, and physical characterization of transition-metal complexes of new carbon-containing ligands constitute important ongoing objectives of organometallic chemists. In the presence of metallic heterogeneous or homogeneous catalysts, synthesis gas can be converted to a variety of organic molecules (methane, methanol, higher alkanes and alcohols, and glycols). In advance of any experiment, formyl complexes appear deceptively easy to synthesize. Comparisons to methods for transition metal acyl synthesis are instructive. Unfortunately, formic acetic anhydride is not a general reagent for formyl complex synthesis. Formyl complexes are characterized by distinct spectroscopic features. Transition-metal formyl complexes are capable of donating hydride to several classes of substrates, of which ketones and aldehydes are prototypical. A unique reaction of formyl complexes is formyl transfer, in which the formyl ligand undergoes apparent migration from one metal to another. Reactions of neutral formyl complexes with alkylating agents can follow different courses. Formyl complexes show varying behavior when treated with protonating agents. Anionic formyl complexes can be reduced when treated with the more potent trialkylborohydride nucleophiles. Neutral formyl complexes that contain ligating CO often decompose by decarbonylation; however, several exceptions exist. It is evident that transition-metal formyl complexes possess a unique and rich chemistry. 1982 Academic Press Inc.
