Localization of ferrocene in NaY zeolite by powder x-ray and neutron diffraction

Abstract

We study the inclusion of the metallocene ferrocene Fe͑C 5 H 5 ) 2 molecules in the supercages of NaY zeolite. To find the exact location of the ferrocene molecules within the supercages we perform neutron and powder x-ray diffraction on bare NaY zeolite, and on NaY zeolite loaded with one or two ferrocene molecules per supercage. Using the complementary properties of both techniques we show that the ferrocene molecules are located just above a line joining two neighboring sodium ions at the SII positions in the zeolite supercage. The C 5 H 5 rings are oriented towards the sodium ions in an ordered manner. This structure is confirmed by quantum chemistry calculations. The geometry of the ferrocene molecules barely changes, indicating that the increased reactivity of ferrocene upon adsorption in a zeolite is thus a result of the position of the molecules. The main interactions responsible for this position are Coulombic attraction and hydrogen bonding. The inclusion of ferrocene in a Y-type zeolite provides a homogeneous distribution of iron throughout the zeolite at well-defined locations.

Structure and Enhanced Reactivity of Chromocene Carbonyl Confined inside Cavities of NaY Zeolite

“…(1) The Cp rings of the Cp 2 Cr molecule are slightly negatively charged; therefore, it seems natural that they orient toward Na + cations by electrostatic interactions (Figure 1), as in the case of ferrocene. 5,84,85 These interactions, responsible for the position of the Cp 2 Cr molecule found inside the NaY host, could also be the driving forces of the subsequent Cp ligand loss under a CO environment. (2) To take into account the stoichiometry of the process, the simultaneous presence of more than one Cp 2 Cr molecule inside the same supercage is necessary.…”

“…Two Cp 2 Cr molecules were placed inside the NaY supercage, with an interaction geometry similar to that found in the case of FeCp 2 encapsulated inside NaY. 5 In that case, X-ray and neutron diffraction reveal that, in the presence of FeCp 2 , the Na + cations are shifted toward the center of the supercage, suggesting an interaction between these ions and the Cp rings of the FeCp 2 molecule. b The optimized S 0 2 values for CrCp 2 molecules in nonpolar media, like toluene or polystyrene, or in the bulk phase are in the 0.6-0.75 range, i.e., significantly lower than the unit value.…”

“…The inclusion of organometallic complexes inside cavities of zeolitic host frameworks is a topic that has gained considerable attention since the 1990s because of the possible applications in heterogeneous catalysis or electronic devices and optical materials [1][2][3][4][5][6][7] and because it provides a method for metal incorporation and catalyst immobilization 8,9 inside nanoporous scaffolds, which is an alternative to classical methods such as ion exchange, ligand exchange, and ship-in-the-bottle synthesis. [10][11][12][13][14][15][16][17] The organometallic guests in zeolite hosts become polarized by electrostatic fields resulting from the interplay between positively charged extra-framework cations and negatively charged zeolite walls and are expected to show substantially enhanced reactivity compared to the parent compounds.…”

Formation and reactivity of CrIIcarbonyls hosted in polar and non polar supports

“…In particular, the inclusion of organometallic complexes inside host frameworks gives the possibility of several applications such as electronic devices, optical materials or heterogeneous catalysis. [1][2][3][4][5][6][7] Metallocenes are organometallic substrates of interest to investigate potential reactivity enhancement; among them, chromocene (Cp 2 Cr) is a challenging candidate, both for applicative (being precursor of the well known Union Carbide olefin catalyst 8 ) and for theoretical reasons (because the modeling of open shell systems is still a challenge). [9][10][11][12][13] The experimental approaches adopted so far to investigate the properties and the reactivity of these systems (such as matrix isolation technique 14 and dissolution in a solvent 15,16 ), suffered of some disadvantages.…”

Remarkable Electrochemical Responses of Ferrocene/NaY Zeolite Composite modified Electrode Based on Hydrophobic Ionic Liquid

“…In addition, it should be noted that more boundary sites or surface sites are present due to the smaller particle size of zeolite (about 400 nm). Based on these facts, ferrocene species, which are easily accessible to electrons transfer, are not entirely external ferrocene, but located either in near-surface sites, supercages of outer cavities, broken cages or boundary sites [23] and weakly bonded with zeolite framework by electrostatic attraction and hydrogen bonding [24]. The efficiency of Fc/NaY/IL-GC-modified electrode could be evaluated by redox probe molecules.…”