Reactions of the Si-H functionalized silicon-bridged [1]ferrocenophane Fe(η-C5H4)2SiMeH with dicobalt octacarbonyl:: Ring-opening metalization and the synthesis of a novel sila[1]ferrocenophane with a Co(CO)4 substituent

Reaction of Co-2(CO)(8) with the Si-H-functionalized sila[1]ferrocenophane Fe(eta -C5H4)(2)SiMeH (la) was found to result in metalation of silicon and ring-opening of the ferrocenophane, affording the orange crystalline silylene-bridged dicobalt heptacarbonyl complex (eta -C5H6)-Fe(eta -C5H4)Si[mu -Co-2(CO)(7)](Me) 6 in 45% yield. The novel red, crystalline sila[1]ferrocenophane Fe(eta -C5H4)(2)Si[Co(CO)(4)](Me) (8), the first with a direct Si-M bond, was isolated in 23% yield when the reaction between la and Co-2(CO)(8) was conducted in NEt3 as a proton trap. The dinuclear complex 6 and metalated silicon-bridged ferrocenophane 8 were each characterized by multinuclear NMR spectroscopy, mass spectrometry, and single-crystal X-ray diffraction. [1]Ferrocenophanes Fe(eta -C5H4)(2)Si(Et)(H) (9) and Fe(eta -C5H4)(2)Si(Me)(D) (10) were prepared in order to investigate whether the ring-opening reaction that afforded 6 was an intramolecular or an intermolecular process. Mass spectral analysis of the products of the reaction of an equimolar mixture of 9 and 10 with Co-2(CO)(8) showed only the presence of (eta -C5H5)-Fe(eta -C5H4)Si[mu -Co-2(CO)(7)](Et) (11) and (eta -C5H4D)Fe(eta -C5H4)Si[mu -Co-2(CO)(7)](Me) (12); neither (eta -C5H4D)Fe(eta -C5H4)Si[mu -Co-2(CO)(7)](Et) (11') nor (eta -C5H5)Fe(eta -C5H4)Si[mu -Co-2(CO)(7)](Me) (12') were detected, which indicated that the ring-opening process was intramolecular. Compounds 11 and 12 were synthesized separately to provide comparative spectroscopic data for the mechanistic investigation.