Iron complexes of (E)- and (Z)-1,2-dichlorodisilenes

Novel disilene-iron complexes [(E)- (1E) and (Z)-(η²-R₃SiClSi=SiClSiR₃)Fe(CO)₄ (1Z), SiR₃ = ^tBu₂MeSi] were synthesized by the reaction of the corresponding tetrachlorodisilane with an excess amount of K₂Fe(CO)₄, and the structures of 1E and 1Z were determined by X-ray crystallography. These complexes constitute not only the first transition-metal complexes with E,Z-isomerism but also the first complexes with halogen-substituted disilene ligands. The initial formation of 1Z during the synthetic reaction and the slow one-way isomerization of 1Z to 1E are rationalized by the intervention of the corresponding silylene complex (R₃SiCl₂Si)(R₃Si)Si=Fe(CO)₄.