Synthesis and characterization of the inclusion compound of a ferrocenyldiimine dioxomolybdenum complex with heptakis-2,3,6-tri-O-methyl- β-cyclodextrin

A dioxomolybdenum(VI) complex bearing the diimine ligand N,N′-bis(ferrocenylmethylene)ethylenediamine (FcNN) has been prepared in good yield by the reaction of FcNN with MoO₂Cl₂(THF) ₂. One isomeric form was identified by ¹H NMR (including NOE experiments), corresponding to the cis,cis geometry with respect to the CN bonds of the free ligand. The polynuclear complex was immobilized in permethylated β-cyclodextrin (TRIMEB) by addition of the guest to a solution of TRIMEB in a mixture of dichloromethane and nitromethane. Removal of the solvent led to the isolation of an inclusion compound with a 2:1 host:guest stoichiometry. For comparison, an inclusion compound containing just the ligand FcNN and TRIMEB was prepared using a similar method. The products were characterized in the solid state by powder X-ray diffraction (XRD), thermogravimetric analysis (TGA), FT-IR and ¹³C CP MAS NMR spectroscopy. UV-Vis measurements were also carried out in solution. Both the complex MoO₂Cl₂(FcNN) and its inclusion compound with TRIMEB catalyze with high selectivity the liquid phase epoxidation of cyclooctene using tert-butyl hydroperoxide (TBHP) as the oxidant. In general, the catalytic behavior of the Mo^VI complex was not markedly affected by encapsulation in TRIMEB, although observed activities were slightly lower.