RUTHENIUM CARBONYL CLUSTERS IN FAUJASITE CAGES - SYNTHESIS AND CHARACTERIZATION

The synthesis of the intrafaujasite anchoring of ruthenium carbonyl cl usters involves the adsorption of metal carbonyl species or metal ion exchange into faujasite cages followed by reductive carbonylation unde r an atmosphere of CO and H-2. The characterization of the structure a nd properties of these samples was based on a multianalytical approach , including FT-IR, UV-vis, PXRD, and EXAFS spectroscopies, CO/H-2 gas chemisorption, and (CO)-C-13 isotopic exchange. From this study, sever al key points emerge. (a) [Ru-3(CO)(12)] clusters thermally diffused i nto dehydrated faujasite cages. (b) [Ru-3(CO)(12)] guests in Na56Y wer e thermally activated, in a hydrogen atmosphere, generating intrafauja site [H4Ru4(CO)(12)]. (c) Hexammineruthenium(III) complexes in Na56X a nd Na56Y underwent progressive thermal activation, in a CO and H-2 atm osphere. The generation process was considered to occur through conver sion of the intermediates [Ru(NH3)(5)(CO)](2+) and Ru-1(CO)(3) to [Ru- 6(CO)(18)](2-). (d) A rapid (CO)-C-13/ (CO)-C-12 isotopic exchange was found to reversibly occur for [Ru-6(CO)(18)](2-)/Na56X under H-2 coex istence. (e) Internal and external confinement of ruthenium carbonyl c lusters were compared. (f) Oxidation fragmentation under an O-2 atmosp here and reductive regeneration under a CO and H-2 atmosphere were fou nd to reversibly occur for [Ru-6(CO)(18)](2-) guests. (g) Intrafaujasi te anchoring of ruthenium carbonyl clusters showed a strong interactio n with the extraframework Na+ alpha-cage cations, through involvement of the oxygen end of the bridging or equatorial terminal carbonyl liga nds.