Iron carbonyl complexes of dimethyl cyclooctatetraene-1,8-dicarboxylate

Article abstract of DOI:10.1021/om00084a003

Reaction of dimethyl cyclooctatetraene-1,8-dicarboxylate with iron carbonyls yields, in addition to the known 3-6-η⁴-Fe(CO)₃ complex, two new Fe₂(CO)₆ complexes. One is a yellow 1-4-η⁴,5-8-η⁴-bis[Fe(CO)₃] complex, with the iron tricarbonyl groups probably trans. The other is a red compound with a 1,5,6-η³,2-4-η³-Fe₂(CO) ₆(Fe-Fe) structure. The X-ray crystallographic structure of the latter compound shows an iron-iron distance of 2.771 A? and indicates a strong interaction of the Cl-bound ester group with the C-Fe σ-bond. The red Fe₂(CO)₆(Fe-Fe) complex is the most stable, probably as a consequence of that interaction. None of the compounds exhibits haptotropy at room temperature, in contrast to the parent hydrocarbon complexes.