ON THE COMPLEX CHEMISTRY OF CYCLOPENTADIENYL LIGANDS WITH OLIGOETHYLENE GLYCOL ETHER TENTACLES

The potassium cyclopentadienides KCp'[SiMe2(OCH2CH2)m-OCH3]n (2) react with trimethyltin chloride to give the respective stannanes Me3SnCp'[SiMe2(OCH2CH2)mOCH3]n (3a-e). Reaction of 2a-e with iron(II) chloride affords the ferrocenes Fe{Cp'[SiMe2(OCH2CH2)mOCH3]n}2 (4a-e), which are soluble in solvents of all polarities. 4a-d were investigated with respect to their ability to act as podands for alkaline metal cations. 4c, d prove to be much better podants than 4a, b; 4a, c show a certain selectivity for K+, 4b, d show a preference for Cs+. Without rigorous exclusion of moisture, 4e yields the tetrasiladioxa[3](1,1')[3](3,3')ferrocenophane 5 upon prolonged standing at room temperature. The structure of 5 was determined by a single-crystal X-ray diffraction study. The molecule is essentially unstrained with the cyclopentadienyl rings being exactly parallel to each other; the distance between the iron atom and the ring centroid is 165 pm.