Low-temperature treatment of ferric chloride with organolithium compounds in the presence of chelating N-donor ligands gave an array of new ferrous alkyl complexes. TMEDA (N,N,N′,N′-tetramethylethylenediamine) stabilizes the mixed alkyl/chlorido complexes (TMEDA)FeCl(CH3) and (TMEDA)FeCl(CH2SiMe3), as well as the dineosilyl complex (TMEDA)Fe(CH2SiMe3)2. Efforts to synthesize the dimethyl species led to the formation of higher alkylated iron lithium ate complexes including the long sought after Li2Fe(CH3)4 entity. Switching to sterically slightly more demanding TEEDA (N,N,N′,N′-tetraethylethylenediamine) gave access to elusive (TEEDA)Fe(CH3)2 and complexes analogous to the ones obtained with TMEDA. The paramagnetic complexes were characterized using 1H/7Li NMR and FTIR spectroscopy, as well as single crystal X-ray diffraction. Investigations toward their C(sp2)–C(sp3) cross-coupling reactivity and comparison to their respective in situ generated mixtures revealed an unprecedented dependence of the product Z–E isomerism on the employed reactant ratio.
Odenwald et al. (Mon,) studied this question.