The anchoring chemistry, thermal stability, and reactivity of M~J S~M~( C O )~ in zeolite NaY and acid forms of zeolite Y was studied with X-ray absorption spectrosc~py (Sn, Mn edge EXAFS) and in situ lTIR/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 MII(CO)~ moiety indicate interaction with the Na' ions of the zeolite framework. The intrazeolite complex in NaY is accessible to external reactants and undergoes carbonyl substitution with PEt, at the manganese center. At 393 K under vacuum, the Mn-CO ( N = 3.9, R = 1.79 A) and Mn-CO coordination (N = 4.3, R = 2.96 A) derived from EXAFS data shows that mast of the CO coordination sphere is still intact. The intrazoolite complex decomposes at about 423 K by loss of all CO ligands and, subsequently, cleavage of the Sn-Mn bond. Mn and Sn cluster species are formed at 523 K. In contrast to Nay, the acidic HY host interacts with the Me& moiety of the bimetallic complex. The compound attaches to the zeolite framewotk 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, gas while the Sn-Mn bond and the CO ligand sphere are still intact. Different degrees of substitution of the methyl group by the acidic oxygen framework are observed. Both mom and disubstituted species, (Oz)M~nMn(CO), and (OZ)~MCS~M~(CO)~, 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 A, Mn-CO, R = 2.97 A), 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. IntroductionThe quest for well-defined, stable hybrid catalysts containing organometallic species continues.'J Facile separation of the products from the catalyst as well as novel means to enhance selectivity are important promising features of hybrid catalysts. The crystalline channel systems of zeolites (open framework oxide

The intracavity chemistry of [CpFe(C0),I2 (1) and ferrocene in different acid forms of zeolite Y has been studied with EXAFS, in situ FTIR, and TPD-MS spectroscopies. Depending on the stoichiometry of zeolite protons vs the amount of starting complex 1, the complex is either oxidatively cleaved into CpFe(CO)3f ( 2 ) and CpFe' coordinated to the zeolite, or protonated to form dimeric [CpFe(C0)2]2H' (3). It is shown that the stability of all complexes is influenced by the intracavity concentration of the zeolite-bridged hydroxyl groups. The cationic monomer 2 is stable up to 500 K in the highly acidic zeolite host, whereas the protonated dimer decomposes above 400 K. At higher temperatures, all carbonyl ligands are split off from the iron complexes, and the remaining dominant fragments are identified as CpFe(OZ), (n = 2-3), bonded to the zeolite host structure via oxygen coordination. Similar fragments are formed upon thermal decomposition of ferrocene in the zeolite.

HY zeolite encapsulated Cl,(thf)GeMo(CO), (thf = tetrahydrofuran), studied by EXAFS, in situ Fourier transform spectroscopy, and temperature programmed desorption (TPD) MS, attaches to the zeolite pore system through the Ge-moiety with retention of the Ge-Mo bond, whereas a large fraction of the intrazeolite -MO(CO)~ moieties remain unaffected by the anchoring reaction.

The intrazeolite reactivity of (COT)Fe(CO)3 (COT = cyclooctatetraene) [ 11 in faujasites having different levels of Bronsted acidity was examined with extended X-ray absorption fine structure, vibrational, and temperature programmed desorption/mass spectrometric techniques. The data show that the precursor complex [ l ] associates with Na-Y zeolite, resulting in symmetry changes of the Fe(C0)3 fragment while 1 remains chemically intact. If (COT)Fe(CO)3 is adsorbed into highly acidic H-Y zeolite at room temperature, bicyclo[5.1 .O]octadienyliron tricarbonyl cation is formed in a clean reaction. This reaction corresponds to the protonation of 1 with noncoordinating acids in homogeneous solution. At elevated temperatures, the carbonyl ligands are cleaved off and the remaining organo-iron fragment is anchored to framework oxygens of the large zeolite supercages. IntroductionMany organometallic complexes have successfully been used in homogeneous catalysis. Often these catalyst systems are highly selective and allow mild reaction conditions to be used. However, difficult separation of the catalyst from the products or deactivation due to irreversible structural changes can compromise the benefits of homogeneous catalytic systems. In an attempt to combine the advantages of both homogeneous and heterogeneous systems, molecular catalysts have in the past been supported on various metal oxides. A wide range of transition-metal s-allyl, cyclopentadienyl (Cp), carbonyl, and olefin derived catalyst precursors have been prepared during the past decade, including group IV, VI, and VI11 metal species supported on amorphous oxides. '-5 In contrast to classical amorphous catalyst supports, the crystalline pore structure of zeolites offers a unique potential to control substrate access through diffusional selectivity and to modify catalytic transition states. The present study is part of a research program aimed at the synthesis of well-defined, stable hybrid catalysts by anchoring transition-metal species into zeolite supports. We explore the reactivity of transition-metal complexes in acid forms of zeolites. Anchoring of metal species into the zeolite cavities can in principle be achieved by substituting leaving groups at the transition-metal complex with zeolite oxygen. As a basis for the rational design of zeolite-based hybrid catalysts, we study the different relative reactivities and stabilities of ligands at a metal center with respect to the bridged intrazeolite hydroxyls (ZOH). In this study, the intrazeolite reactivities of cyclooctatetraene (COT) and carbonyl ligands of (COT)Fe(C0)3 [ 11 have been examined.The protonation of (COT)Fe(C0)3 in homogeneous solution has been well studied. Key reactions are summarized in Scheme

The surface chemistry of the two germylene complexes C12(THF)GeM(C0)5 (M = Mo (1) and W ( 2 ) ) in zeolite Y was studied with X-ray absorption spectroscopy (Ge, Mo, W edge EXAFS) and in situ FTIR/TPD-MS techniques. The molybdenum complex 1 interacts with the framework of Na-Y zeolite at room temperature where decarbonylation occurs to a small extent. The intrazmlite 1 retains the GeMo bond up to about 120 OC. In proton-loaded H-Y zeolite, framework interactions increase with temperature, and the G t M o bond is retained up to about the same temperature. At higher temperatures, the G t M o bond is cleaved and MoCl, and Mo-Mo species are formed in the Na-Y and H-Y forms, respectively. GeCl, fragments attach to both zeolite frameworks. The intrazeolite complex C12(THF)GeW(CO)S (2) retains all five carbonyl ligands up to about 100 OC in both Na-Y and the proton form. Significant anchoring through the Ge moiety is observed at room temperature in Na-Y and at about 80 OC in the proton form. The intrazeolite stability of the anchored G t W complex is somewhat higher than that of the G t M o analog, and WCl, species are formed upon cleavage of the G e W bond at higher temperatures. The anchoring of the C12(THF)Ge moiety into Na-Y is believed to be based upon a Na+--C1-interaction between Na ions in zeolite coordination sites and the chloride ligands of the precursor. The only gas evolution detected up to about 120 OC is due to partial decarbonylation (CO) and HCl formation in the acid supports. The absence of precursor desorption confirms the effective anchoring of the transition-metal germylene complexes into zeolite cages. IntroductionImmobilization strategies of transition-metal catalysts on heterogeneous supports have attracted increasing attention:'-3 The advantages of many molecular catalysts> such as high selectivity, mild reaction conditions, and utilization of all metal atoms, could potentially be combined with the facile product separation and catalyst recovery inherent in heterogeneous systems. Combined "hybrid" systems could also offer features not present in conventional catalysts: The immobilized, catalytically active centers might be stabilized against aggregation, and they could be used in reaction media in which the original molecular catalyst is insoluble, or even in -lid interface reactions. However, hybrid systems can also present complications, including the frequent instability against leaching of the catalyst metal into solution and agglomeration resulting in (undesired) metal particles with different catalytic reactivity.This article describes a comprehensive study of the chemistry of Gemetal complexes in zeolite cages. As part of our efforts to develop novel immobilization concepts for organometallic fragments in porous solids, we have introduced heterobinuclear compounds as candidates for linking catalytic functions to zeolite frameworks. The premise is that the complexes can be anchored to the support via an oxophilic element, whereas catalytic reactions may proceed at the second metal center. ...