Reactions of N-(2-thienylmethylidene)-2-thienylmethylamine derivatives with diiron nonacarbonyl: characterization and structures of cyclometallated diiron complexes Fe 2(CO) 6(RC 4HSCH 2NCH 2C 4H 3S) and linear tetrairon clusters Fe 4(CO) 10(RC 4HSCHNCH 2C 4H 3S) 2

Abstract

The reaction of N-(2-thienylmethylidene)-2-thienylmethylamine ( 1) with Fe 2(CO) 9 under mild conditions in anhydrous benzene yields the iron carbonyl products 2, 3, and 4. Complex 2 is a cyclometallated complex Fe 2(CO) 6(RC 4HSCH 2NCH 2C 4H 3S), in which the organic ligand is (μ-η 1:η 2-thienyl β-C, α, β-CC; η 1:η 1-(N))-coordinated to the diiron center. Complexes 3 and 4 are novel linear tetrairon complex isomers Fe 4(CO) 8(μ-CO) 2(RC 4HSCHNCH 2C 4H 3S) 2, in which the two organic ligands are (μ-η 1-thienyl β-C: η 1-N;η 2-thienylα, β-CC:η 2-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 Fe 2(CO) 2(μ-CO) 2 core to which two η 5-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.