Synthesis of doubly-bridged Fe/Se and Fe/Te complexes via reactions of the [MgX]+ salts of anions [(μ-RE)(μ-CO)Fe2(CO)6]− (E=Se,Te)

The reactions of Grignard reagents RMgX with elemental Se or Te in THF, followed by treatment of the intermediates RSeMgX or RTeMgX with Fe3(CO)12 at room temperature (r.t.), were found to give [MgX]+ salts of anions [(μ-RSe)(μ-CO)Fe2(CO)6]− (2) and [(μ-RTe)(μ-CO)Fe2(CO)6]− (3), respectively. Furthermore, the [MgX]+ salts of anions 2 (R=Et) reacted in situ with the electrophile Ph2AsCl to afford (μ-EtSe)(μ-Ph2As)Fe2(CO)6 (4), whereas the [MgX]+ salts (R=p-MeC6H4) reacted with the electrophile PhNCS, followed by treatment with another electrophile MeI to give (μ-p-MeC6H4Se)(μ-PhN(Me)CS)Fe2(CO)6 (5). Similarly, the [MgX]+ salts of anions 3 (R=Et, t-Bu, i-Bu) were found to react sequentially with the electrophiles PhCCPh and CF3COOH to yield (μ-RTe)(μ-σ,π-PhCCHPh)Fe2(CO)6 (6a, R=Et; 6b, R=t-Bu; 6c, R=i-Bu), whereas reactions of the [MgX]+ salts of anions 3 (R=Et, Ph, p-MeC6H4) with the electrophiles Ph2AsCl or PhC(Cl)NPh produced (μ-RTe)(μ-Ph2As)Fe2(CO)6 (7a, R=Et; 7b, R=p-MeC6H4) and (μ-RTe)(μ-PhCNPh)Fe2(CO)6 (8a, R=a(axial)-Ph; 8b, R=e(equatorial)-Ph; 9a, R=a-p-MeC6H4; 9b, R=e-p-MeC6H4), respectively. The reaction courses for the formation of Fe/Se and Fe/Te complexes 4–9 were discussed briefly and the structures of these new complexes, along with two other new Fe/Te complexes (μ-RTe)2Fe2(CO)6 (R=Et, i-Bu), were characterized by elemental analysis and spectroscopy, as well as for complex 9b, whose structure was confirmed further by X-ray diffraction analysis.