The reactions of heterocyclic organotellurium and selenium compounds with triiron dodecacarbonyl

Abstract

The reaction of 2-telluraphthalide, C₈H₆OTe, with [Fe₃(CO)₁₂] gave as the major characterised species compound 1, [C₆H₄CH₂TeFe(CO)₃]₂. An iron atom has inserted into the telluracyclic ring, and it is probable that one co-ordinated CO ligand arises from the initially organic carbonyl group. X-Ray single crystal investigations revealed a dimeric structure containing an Fe₂Te₂ core. The reaction of 2-telluraphthalic anhydride, C₈H₄O₂Te, with [Fe₃(CO)₁₂] gave a known, but unexpected, organic product phthalide, C₈H₆O₂. X-Ray crystallography confirmed its isolation; the main feature of interest is the significant double bond character of C(8)–O(1) at 1.352(4) Å. 2-Selenaphthalic anhydride, C₈H₄O₂Se, gave intractable products on reaction with [Fe₃(CO)₁₂], but 2-selenaphthalide, C₈H₆OSe, on reaction with the carbonyl gave a major product 2, [Fe(CO)₃{C₆H₄CH₂SeFe(CO)₃}] and a minor product 3, [Fe(CO)₂{η⁶-C₆H₄CH₂SeFe₂(CO)₆}] which is an intermediate in the formation of 2. Compound 2 was shown by X-ray methods to be very similar to 1 except that the 18 electron rule is satisfied by co-ordination of an Fe(CO)₃ moiety, rather than by dimerisation. Compound 3, also studied by X-ray crystallography, differs from 2 mainly in the addition of an η⁶-bonded Fe(CO)₂ moiety, but the selenaferrole ring is more distorted. It is proposed that comparative studies of reactions of selenium and tellurium compounds with [Fe₃(CO)₁₂] may assist the development of an understanding of the complex reaction pathways.