Two new bidentate ligands, C5H5Me2SiGeMe2C5H5 (9) and C5HMe4Me2SiGeMe2C5HMe4 (10) were prepared by the reaction of CiMe2 SiGeMe2Cl with cyclopentadienyl lithium and tetramethylcyclopentadienyl lithium, respectively. Ligands 9 and 10 reacted with Fe(CO)5 to yield the diiron complexes (Me2SiGeMe2)- [ (η^5-C5R4)Fe(CO)]2(μ-CO2)(R=H, 11; R=Me,13). Complexes 11 and 13 could form the products [(η^5-C5R4)Fe(CO)2]2(μ-Me2Si) (μ-Me2Ge) (R=H, 12; R=Me,14) by a novel intramolecular thermal rearrangement reaction. The crystal and molecular structures of complexes 11, 12,13 and 14 were determined by X-ray diffraction. The steric effect of the bridged tetramethylcyclopentadienly ligand on some structural data and the rearrangement reactivity was discussed.

Key words: CYCLOPENTADIENE P, ORGANO SILICON COMPOUNDS, ORGANO GERMANIUM, CARBONYL COMPOUNDS, IRON COMPLEX, CRYSTAL STRUCTURE