The reactions of heterocyclic organotellurium and selenium compounds with triiron dodecacarbonyl

The reaction of 2-telluraphthaIide, C8H6OTe, with [Fe-3(CO)(12)] gave as th e major characterised species compound 1, [C6H4CH2Fe(CO)(3)](2). An iron at om has inserted into the telluracyclic ring, and it is probable that one co -ordinated CO ligand arises from the initially organic carbonyl group. X-Ra y single crystal investigations revealed a dimeric structure containing an Fe,Te, core. The reaction of 2-telluraphthalic anhydride, C8H4O2Te, with [F e-3(CO)(12)] gave a known, but unexpected, organic product phthalide, C8H6O 2. X-Ray crystallography confirmed its isolation; the main feature of inter est is the significant double bond character of C(8)-O(1) at 1.352(4) Angst rom. 2-Selenaphthalic anhydride, C8H4O2Se, gave intractable products on rea ction with [Fe-3(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){eta(6)-C6H4CH2SeFe2(CO)(6)}] which is an interm ediate in the formation of 2. Compound 2 was shown by X-ray methods to be v ery similar to 1 except that the 18 electron rule is satisfied by co-ordina tion 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 eta(6)-bonded Fe(CO)(2) moiety, but the selenaferrole ring is more disto rted. It is proposed that comparative studies of reactions of selenium and tellurium compounds with [Fe-3(CO)(12)] may assist the development of an un derstanding of the complex reaction pathways.