Reactions of N-(2-thienylmethylidene)-2-thienylmethylamine derivatives with diiron nonacarbonyl: characterization and structures of cyclometallated diiron complexes Fe2(CO)6(RC4HSCH2NCH2C4H3S) and linear tetrairon clusters Fe4(CO)10(RC4HSCHNCH2C4H3

The reaction of N-(2-thienylmethylidene)-2-thienylmethylamine (1) with Fe2(CO)9 under mild conditions in anhydrous benzene yields the iron carbonyl products 2, 3, and 4. Complex 2 is a cyclometallated complex Fe2(CO)6(RC4HSCH2NCH2C4H3S), in which the organic ligand is (μ-η1:η2-thienyl β-C, α, β-CC; η1:η1-(N))-coordinated to the diiron center. Complexes 3 and 4 are novel linear tetrairon complex isomers Fe4(CO)8(μ-CO)2(RC4HSCHNCH2C4H3S)2, in which the two organic ligands are (μ-η1-thienyl β-C: η1-N;η2-thienylα, β-CC:η2-CN)-coordinated to two diiron centers, respectively. These complexes were well characterized spectrally. The molecular structures of 1a, 2a, 2b, 3a, and 3b have been determined by means of X-ray diffraction. The linear arrangement of the four iron atoms in the 66e clusters 3 and 4 is consistent with the closed valance molecular orbital (CVMO) theory. Complexes 3 and 4 may be viewed as consisting of a central Fe2(CO)2(μ-CO)2 core to which two η5-azaferracyclopentadieny fragments are coordinated; hence 3 and 4 are isolobally-related analogues of [CpFe(CO)(μ-CO)]2. Thermal reaction of 3 or 4 in hexane, benzene, or acetonitrile leads to the decomposition of the complex. No interconversion between isomers 3 and 4 has been observed.