Novel route to iron-carbene derivatives via addition of alkynes to carbon disulfide-iron complexes. Rearrangement of (1,3-dithiol-2-ylidene)iron complexes into heterometallacycles

Abstract

Addition of a variety of alkynes, containing a formyl, acyl, or carboxylate group, to a benzene solution of Fe(v2-CS2)(CO),[P(OMe),], produces carbene-iron complexes (A), the (1,3-dithiol-2-ylidene)iron derivatives 2 resulting from the bonding of both sulfur atoms to the alkyne carbons. The reaction of dimethyl acetylenedicarboxylate with F~(T~-CS,)(CO)~L, affords the carbene complex A which is stable when L is P(OMe), or PPh, but isomerizes into a heterometallacycle (B) for L = PMe3 and gives the A * B equilibrium when L = PMe2Ph. The cycloaddition of the alkyne to the CS2 ligand is shown to be reversible. The A * B equilibrium constant and the rate of the isomerization of A increase with the electron-donating capability of the ligand L. 1,3-Dipolar cycloaddition of the alkyne to the FeCS, moiety may account for these reactions.