Experimental and theoretical study of the encapsulation of a linear oligo(ferrocenylsilane) trimer with β-cyclodextrin

An inclusion compound comprising P-cyclodextrin (P-CD) and the trimetallic oligo(ferrocenylsilane) FcSiMe(2)[(eta(5)-C5H4)Fe( eta(5)-C5H4SiMe2)]Fc [Fc = (eta(5)-C5H5)Fe(eta(5)-C5H4)] has been prepared and characterised in the solid state by elemental analysis, powder X-ray diffraction, thermogravimetric analysis and magic angle spinning NMR spectroscopy (C-13, Si-29). The results are consistent with the formation of a 2:1 (host-to-guest) inclusion complex. Ab initio calculations were carried out in order to investigate the possible inclusion geometries. The best host-guest fit was obtained for a tilted geometry of the ferrocene fragment relative to the beta-CD axis (phi = 29 degrees) with a 140-pm inclusion of the corresponding Fe centre below the plane of the rim. The structure of the organometallic trimer allows its inclusion interaction with a second beta-CD host, leading to the 2:1 stoichiometry. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005).