Reactivity of (trimethyl stannyl)pentacarbonylmanganese in zeolite cavities

Abstract

The anchoring chemistry, thermal stability, and reactivity of Me{sub 3}SnMn(CO){sub 5} in zeolite NaY and acid forms of zeolite Y was studied with X-ray absorption spectroscopy (Sn, Mn edge EXAFS) and in situ FTIR/TPD-MS techniques. In the NaY host, the precursor is physically adsorbed from hexane solution into the dehydrated zeolite cages at room temperature without further chemical reaction. Symmetry changes of the Mn(CO){sub 5} moiety indicate interaction with the Na{sup +} ions of the zeolite framework. At 393 K under vacuum, the Mn-CO (N = 3.9, R = 1.79 {angstrom}) and Mn-CO coordination (N = 4.3, R = 2.96 {angstrom}) derived from EXAFS data shows that most of the CO coordination sphere is still intact. The intrazeolite complex decomposes at about 423 K. In contrast to NaY, the acidic HY host interacts with the Me{sub 3}Sn moiety of the bimetallic complex. The compound attaches to the zeolite framework at the oxygen rings of the supercage already at room temperature. The attachment of the molecule occurs through the Sn moiety by loss of CH{sub 4} gas while the Sn-Mn bond and the CO ligand sphere are still intact. Different degrees of substitution of the methyl groups by the acidic oxygenmore » framework are observed. Both mono- and disubstituted species, (Oz)Me{sub 2}SnMn(CO){sub 5} and (Oz){sub 2}MeSnMn(CO){sub 5}, are formed under retention of the Sn-Mn bond. At room temperature, the monosubstitution is favored while disubstitution is more pronounced at higher temperature, i.e., 373 K. At this temperature, the Mn-CO coordination data still indicate five CO ligands (Mn-CO, R = 1.84 {angstrom}, Mn-CO, R = 2.97 {angstrom}), and the Sn-Mn bond is still intact (N = 0.9, R = 2.58). After the Sn-Mn bond is cleaved at 423 K, Sn is still anchored to the zeolite framework through oxygen coordination while Mn cluster species are formed. At 523 K, both Sn and Mn are attached to the zeolite oxygen framework. 28 refs., 11 figs., 3 tabs.« less