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) [eta(5)-C5H4Fe (CO)(2)Na](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) [eta(5)-C5H4Fe (CO)(2)R](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.