Iron Complexes of (<i>E</i>)- and (<i>Z</i>)-1,2-Dichlorodisilenes

Novel disilene−iron complexes [(<i>E</i>)- (<b>1E</b>) and (<i>Z</i>)-(η<sup>2</sup>-R<sub>3</sub>SiClSiSiClSiR<sub>3</sub>)Fe(CO)<sub>4</sub> (<b>1Z</b>), SiR<sub>3</sub> = <i><sup>t</sup></i><sup></sup>Bu<sub>2</sub>MeSi] were synthesized by the reaction of the corresponding tetrachlorodisilane with an excess amount of K<sub>2</sub>Fe(CO)<sub>4</sub>, and the structures of <b>1E</b> and <b>1Z</b> were determined by X-ray crystallography. These complexes constitute not only the first transition-metal complexes with <i>E</i>,<i>Z</i>-isomerism but also the first complexes with halogen-substituted disilene ligands. The initial formation of <b>1Z</b> during the synthetic reaction and the slow one-way isomerization of <b>1Z</b> to <b>1E </b>are rationalized by the intervention of the corresponding silylene complex (R<sub>3</sub>SiCl<sub>2</sub>Si)(R<sub>3</sub>Si)SiFe(CO)<sub>4</sub>.