SYNTHESIS AND STRUCTURE OF SILA-BRIDGED BIS(1-INDENYL AND TETRAHYDROINDENYL) TETRACARBONYL DIIRON COMPLEX

Sila-bridged bis(1-indenyl) tetracarbonyl di-iron complexes E[IndFe(CO )](2)(mu,-CO)(2) (E = Me2Si, 1; Me2SiOSiMe2, 2) have been synthesized by the reaction of Fe(CO)(5) and the corresponding sila-bridged bisind enyl ligands. Both 1 and 2 have cis and trans isomers. According to th e different crystal shapes a small amount of pure cis isomer 1c and tr ans isomer 1t were separated mechanically. But only pure trans isomer 2t was obtained by recrystallization. 1 and 2t were hydrogenated in th e presence of PtO2 at atmospheric pressure, and the corresponding tetr ahydroindenyl complexes 3 and 4t were obtained respectively. After hyd rogenation, pure cis isomer 3c and trans isomer 3t were separated by c hromatography. The crystal structure of the trans isomer It was determ ined by X-ray diffraction. It shows that the unfused moieties of six-m embered rings of indenyl ligands exist as a conjugated diene system. T his explains that 1 and 2 can be readily hydrogenated to the tetrahydr o-indenyl complexes even at atmospheric pressure. (C) 1997 Elsevier Sc ience Ltd.