Akademik Veri Yönetim Sistemi
JOURNAL OF PHYSICAL CHEMISTRY, cilt.95, sa.11, ss.4463-4476, 1991 (SCI-Expanded)
The vibrational and electronic spectroscopy of precursor CpCo(CO)2-M56Y, where M = H, Li, Na, K, Rb, and Cs and Y refers to zeolite Y, is compared with that known for CpCo(CO)2 in the gas, solution, and matrix phases. In this way considerable insight is obtained concerning the subtle interplay of supercage topology, framework oxygen charge density, and extraframework cation local field effects on the geometric and electronic properties, as well as the type(s) of anchoring site(s) (cation versus oxygen framework) found for the guest molecules in the zeolite Y host lattice. These spectroscopic probes also permit one to evaluate the role of these zeolite support effects on the reactivity of anchored CpCo((CO)-C-12)2-M56Y toward (CO)-C-13 isotope exchange, phosphine substitution, and vacuum thermal decarbonylation as compared to the situation found with other supports and in other phases. Information pertinent to the identity and location of precursors and products and their anchoring site architecture (Cp ring versus carbonyl ligand versus cobalt interactions with the zeolite) emerges from the results of these experiments. Molecular graphics investigations allow one to propose topological models that account for the occurrence and nature of two distinct cation-based anchoring sites for precursor CpCo(CO)2-M56Y (ZOM...CpCo(CO)2 denoted site 1 and ZOM...(OC)2CoCp denoted site 2) as well as its in situ vacuum thermal decarbonylation product Cp2Co2(mu-2-CO)2-M56Y (symmetrical ZOM...CpCo(CO)2CoCp...MOZ denoted class I and symmetrical ZOM...(OC)Cp2Co2(CO)...MOZ denoted class II) over the entire alkali-metal cation series.