Synthesis and structure of sila-bridged bis(1-indenyl and tetrahydroindenyl) tetracarbonyl di-iron complex

Abstract

Sila-bridged bis(1-indenyl) tetracarbonyl di-iron complexes E[IndFe(CO)] 2(μ-CO) 2 (E = Me 2Si, 1; Me 2SiOSiMe 2, 2) have been synthesized by the reaction of Fe(CO) 5 and the corresponding sila-bridged bisindenyl ligands. Both 1 and 2 have cis and trans isomers. According to the different crystal shapes a small amount of pure cis isomer 1c and trans isomer 1t were separated mechanically. But only pure trans isomer 2t was obtained by recrystallization. 1 and 2t were hydrogenated in the presence of PtO 2 at atmospheric pressure, and the corresponding tetrahydroindenyl complexes 3 and 4t were obtained respectively. After hydrogenation, pure cis isomer 3c and trans isomer 3t were separated by chromatography. The crystal structure of the trans isomer 1t was determined by X-ray diffraction. It shows that the unfused moieties of six-membered rings of indenyl ligands exist as a conjugated diene system. This explains that 1 and 2 can be readily hydrogenated to the tetrahydro-indenyl complexes even at atmospheric pressure.