Synthesis and characterization of the inclusion compound of a methyltrioxorhenium(VII) adduct of 4-ferrocenylpyridine with b-cyclodextrin Luı ´s Cunha-Silva a , Isabel S. Gonc ¸alves a, *, Martyn Pillinger a , Wen-Mei Xue b , Joa ˜o Rocha a , Jose ´ J.C. Teixeira-Dias a , Fritz E. Ku ¨hn b a Department of Chemistry, University of Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal b Anorganisch-Chemisches Institut der Technischen Universita ¨t Mu ¨nchen, Lichtenbergstrasse 4, D-85747 Garching bei Mu ¨nchen, Germany Received 22 April 2002; received in revised form 3 June 2002; accepted 7 June 2002 Abstract An organometallic Lewis base adduct of methyltrioxorhenium(VII) (MTO), comprising the ligand 4-ferrocenylpyridine, has been isolated and characterized. The binuclear complex and also the precursor free ligand have been immobilized in b-cyclodextrin (CD) to give inclusion complexes with a one-to-one stoichiometry. Powder X-ray diffraction (XRD) indicates that the microcrystalline powders obtained are true homogeneous inclusion complexes. This is corroborated by thermogravimetric analysis (TGA), which indicates that the ferrocenylpyridine ligand gains an additional thermal stability upon encapsulation. FTIR and 13 C- solid-state CP MAS NMR spectroscopy confirm that the Re  /N ligation is intact for the included binuclear complex. The NMR results also support the conclusion that the monosubstituted ferrocene derivatives adhere to an inclusion model in which the ferrocene penetrates deeply into the CD cavity in axial mode while the substituent protrudes out. # 2002 Elsevier Science B.V. All rights reserved. Keywords: Cyclodextrins; Inclusion compounds; Lewis base adducts; Methyltrioxorhenium; Ferrocene derivatives 1. Introduction Cyclodextrins (CDs) are cyclic oligosaccharides con- sisting of six, seven or eight (1 0/4)-linked a-D-glucopyr- anose units (a-, b- and g-CD, respectively) [1 /3]. They form inclusion complexes with smaller molecules that fit into their 5  /8A ˚ cavity [3 /5]. Suitable guests include transition metal complexes and organometallic com- pounds bearing hydrophobic ligands such as cyclopen- tadienyl (Cp /h 5 -C 5 H 5 ) and h 6 -arene groups [5,6]. With these ligands, the weaker categories of non- covalent bonding, e.g. van der Waals and charge transfer interactions, assume considerable importance. Encapsulated metallo-organic complexes often exhibit markedly different physical and chemical properties compared with the bulk material, for example, in their nonlinear optical properties [7,8], and ligand substitu- tion/insertion reactions [9,10]. CD are known to bind ferrocene and its derivatives [11  /17], titanocene and molybdenocene dihalides [18,19], aromatic ruthenium complexes [20], mixed sandwich complexes such as [(h 5 - C 5 H 5 )Fe(h 6 -C 6 H 6 )](PF 6 ) [21], and half-sandwich com- plexes such as CpFe(CO) 2 X (X /Cl, Me) [9,10,22], [CpFe(CO) 2 NH 3 ](PF 6 ) [23], CpMn(CO) 3 [24], (h 6 - C 6 H 6 )Cr(CO) 3 [25], Cp?Mo(h 3 -C 3 H 5 )(CO) 2 [26], Cp?Mo(h 3 -C 6 H 7 )(CO) 2 and [Cp?Mo(h 4 -C 6 H 8 )(CO) 2 ]- (BF 4 ) (Cp?/Cp, Ind) [27]. Ferrocene itself forms a 2:1 (host-to-guest) adduct with a-CD, and 1:1 adducts with b and g-CD [11  /14]. On the other hand, the interaction of CD with binuclear organometallic compounds has scarcely been studied [28]. In the present work, 4- ferrocenylpyridine and its 1:1 adduct with methyltriox- orhenium(VII) (MTO) have been immobilized in b-CD and the resulting novel inclusion compounds character- ized by a range of solid-state physicochemical techni- ques. * Corresponding author. Tel.:  /351-234-370200; fax:  /351-234- 370084 E-mail address: igoncalves@dq.ua.pt (I.S. Gonc ¸alves). Journal of Organometallic Chemistry 656 (2002) 281  /287 www.elsevier.com/locate/jorganchem 0022-328X/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved. PII:S0022-328X(02)01635-2