EXAFS studies on the reduction of palladium(II) in X zeolites

Palladium tetraammine ion exchange into zeolite, temperature treatments under different atmospheres, and hydrogen reduction have been studied by EXAFS at the Pd Κ edge. Complete autoreduction is found to take place between 473 and 623 Κ under vacuum. Α bidisperse Pd metal phase is formed which agglomerates at the expense of the small particles upon prolonged heating at 623 Κ. In contrast, a similar treatment under oxygen suppresses autoreduction , and the Pd cations remain in zeolite coordination sites. Additional small amounts of palladium oxide are observed under these conditions. If hydrogen is admitted to the dehydrated, ionic system at 295 K. the oxygen coordination of the Pd disappears and evidence is obtained for the formation of Pd(0) dimers that interact with the framework via a long Pd-0 bond

Surface chemistry of heterobimetallic Ge-M (M = Mo, W) complexes in zeolite Y.

The intrazeolite chemistry of the two germylene complexes Cl2CTHF)GeM(CO)5 (M = Mo, W) was studied with x-ray absorption spectroscopy (Ge, Mo, W edge EXAFS) and in-situ FTIR/TPD-MS techniques. The slightly decarbonylated GeMo complex interacts with the framework of NaY zeolite at room temperature and retains the Ge-Mo bond up to about 100° C. In proton-loaded HY zeolite, framework interactions increase at elevated temperature, and the attached complex retains the Ge-Mo bond up to about 120° C. The Ge-Mo bond is cleaved at higher temperatures. MoClx and Mo-Mo species are formed in NaY and HY zeolite, respectively, while GeClx fragments are anchored to the zeolite framework. The complex Cl2(THF)GeW(CO)5 retains all five CO ligands up to about 100° C in both NaY and the proton form. Detectable anchoring occurs at room temperature in NaY and at about 80° C in the proton form. WC1X species are formed upon cleavage of the Ge-W bond at higher temperatures

Reactivity of a trimethylstannyl molybdenum complex in mesoporous MCM-41

A highly thermostable tin–molybdenum complex is encapsulated into the hexagonal mesoporous channel host MCM-41 and thermally transformed into supported metal clusters

Organometallic fragments in microporous solids: intrazeolite chemistry of (cyclooctatetraene)iron tricarbonyl

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