NEW FEASS CAGE STRUCTURES FROM [CP(+)FE(CO)2]2 (CP(+)=C5ME4ET) AND REALGAR

The reaction of [Cp+Fe(CO)2]2 (Cp+= eta5-C5Me4Et) with equimolar amounts of As4S4 in boiling toluene gives Cp+2Fe2As2S2 (1) and Cp2+Fe2As2S3 (2). Both complexes form with two equivalents of Cr(CO)5THF the bisadducts Cp+2Fe2As2S2.2Cr(CO)5 (3) and Cp+2Fe2As2S3.2Cr(CO)5 (4), respectively. The Cr(CO)5 fragments are bound to the As atoms. X-ray diffraction analyses have been carried out for 1 and 4. The structure of 1 contains two coplanar eta2-AsS bridges which bisect the Fe-Fe vector and are parallel to the Cp+ ligands. Complex 1 is formulated as a 30e tripledecker complex for it contains an As-As distance (2.629(1) angstrom) very close to As-As bonding. The structure of 4 contains a Fe2As2S3 cage. The inorganic ligand is formally built up by two syn oriented AsS units which are bridged by a S atom. Such a view is supported by the conversion of 1 into 2 by reaction with a mild sulfur donator, e.g. As4S4.