Cleavage of the Fe–Fe Bond of (Me2SiSiMe2)[η5-C5H4Fe (CO)2]2 with Na/Hg and Molecular Structure of the Ring-Opened Complex†

The reaction of the title cyclic complex (1) with sodium amalgam in THF resulted in the expected cleavage of the Fe—Fe bond to afford bis-sodium salt (Me2SiSiMe2) [η5-C5H4Fe (CO)2Na]2 (4). The latter was not isolated and was used directly to react with MeI, PhCH2Cl, CH3C(O)Cl, PhC(O)Cl, Cy3SnCl (Cy = cyclohexyl) or Ph3SnCl to afford corresponding ring-opened derivatives (Me2SiSiMe2) [η5-C5H4Fe (CO)3R]2 [5, R=Me; 6, R = PhCH2; 7, R = CH3C(O); 8, R = PhC (O); 9, R = Cy3Sn or 10, R = Ph3Sn]. The crystal and molecular structures of 10 were determined by X-ray diffraction analysis. The molecule took the desired anti conformation around the Si—Si bond. The length of the Si—Si bond is 0.2343(3) nm, which is essentially identical to that in the cyclic structure of 1 [0.2346(4) nm]. This result unambiguously demonstrates that the Si—Si bond in the cyclic structure of 1 is not subject to obvious ring strain.