Highly reduced carbonyls of the early transition metals

Pioneering ventures in low valent carbonyl and related chemistry of titanium, zirconium, hafnium and other early transition elements have been undertaken to discover new classes of organometallic and inorganic materials. Useful synthetic methodology-involving a two step reductive carbonylation of a variety of group 4 halides by alkali metal naphthalenides at low temperatures-has been developed recently in our laboratory. By this procedure the first carbocyclic and anionic derivatives of the unknown Ti(CO)₇, Zr(CO)₇ and Hf(CO)₇ have been obtained. Also, this method provides the first general route to organophosphine carbonyls of zerovalent titanium, zirconium and hafnium. Very recently the initial stabilized "pure" carbonyl complexes of these elements have been obtained in the form of the hexacarbonylmetallate(2-) ions, M(CO)₆^2-.