Highly Reduced Organometallic Anions. 1. Syntheses and Properties of Tetracarbonylmetalate(3—) Anions of Manganese and Rhenium

Reductions of M(CO)₅- and M₂(CO)₁₀ (M = Mn and Re) in hexamethylphosphoramide with sodium metal provide high yields of the “super-reduced” species M(CO)₄^3-, which contain manganese and rhenium in their lowest known oxidation states. Infrared and chemical evidence is presented to corroborate proposed formulations for these salts. Their reactions with electrophilic species including Ph₃ECl (E = Ge, Sn, Pb), Me₃ECl (E = Ge, Sn), Ph₃PAuCl, and benzyl chloride, provide a unique route to new organometallic derivatives of stoichiometry (R3E)2M(CO)4-, (Ph₃PAu)₂M(CO)₄, and (C₆,H₅CH₂-CO)₂Mn(CO)₄-. Physical properties of the anionic derivatives are discussed and compared to those of analogous neutral compounds of iron, ruthenium, and osmium.