Interactions of cationic and neutral molybdenum complexes with beta-cyclodextrin host molecules

The inclusion compounds formed between Beta-cyclodextrin (beta-CD) and the tetrafluoroborate salts [Cp' Mo(eta (4)-C6H8)(CO)(2)] [BF4] and the neutral derivatives Cp' Mo(eta(3)-C6H7)(CO)(2) [Cp' = Cp (eta (5)-C5H5), Ind (eta (5)-C9H7)] were studied by means of elemental analysis, FTIR spectroscopy, thermogravimetric analysis (TG;A), powder X-ray diffraction (XRD, and magic -angle spinning (MAS) NMR (C-13, B-11). Additional information concerning t he possible structure of the inclusion compounds was-obtained from ab initi o calculations using a two-layer approximation. The cationic and neutral et a (5)-cyclopentadienylanalogues form stable two-to-one (host; to-guest) cha nnel-type inclusion compounds in a crystalline state. By contrast, the eta( 5)-indenyl analogues form only weak complexes with beta -CD and it is evide nt that the organometallic guests are easily liberated from the host caviti es. The ab initio calculations revealed that the steric hindrance arising f rom the presence of the indenyl ligand is a possible explanation for the ex perimentally observed lower stability of these compounds.