Structures of zeolite-anchored organorhodium complexes undergoing conversions with gas-phase reactants were characterized by infrared spectra bolstered by calculations with density functional theory and analysis of the gas-phase products. Structurally well-defined zeolite-supported rhodium diethylene complexes were synthesized by chemisorption of Rh(C(2)H(4))(2)(acac) (acac = CH(3)COCHCOCH(3)) on dealuminated Y zeolite, being anchored by two Rh-O bonds, as shown by extended X-ray absorption fine structure (EXAFS) spectroscopy. In contrast to the nonuniformity of metal complexes anchored to metal oxides, the near uniformity of the zeolite-supported species allowed precise determination of their chemistry, including the role of the support as a ligand. The anchored rhodium diethylene complex underwent facile, reversible ligand exchange with deuterated ethylene at 298 K, and ethylene ligands were hydrogenated by reverse spillover of hydrogen from support hydroxyl groups. The supported complexes reacted with CO to form rhodium gem-dicarbonyls, which, in the presence of ethylene, gave rhodium monocarbonyls. The facile removal of ethylene ligands from the complex in H(2)-N(2) mixtures created coordinatively unsaturated rhodium complexes; the coordinative unsaturation was stabilized by the site isolation of the complexes, allowing reaction with N(2) to form rhodium complexes with one and with two N(2) ligands. The results also provide evidence of a new rhodium monohydride species incorporating a C(2)H(4) ligand.

High level electronic structure calculations were used to evaluate reliable, self-consistent thermochemical data sets for the third row transition metal hexafluorides. The electron affinities, heats of formation, first (MF(6) --> MF(5) + F) and average M-F bond dissociation energies, and fluoride affinities of MF(6) (MF(6) + F(-) --> MF(7)(-)) and MF(5) (MF(5) + F(-) --> MF(6)(-)) were calculated. The electron affinities which are a direct measure for the oxidizer strength increase monotonically from WF(6) to AuF(6), with PtF(6) and AuF(6) being extremely powerful oxidizers. The inclusion of spin orbit corrections is necessary to obtain the correct qualitative order for the electron affinities. The calculated electron affinities increase with increasing atomic number, are in good agreement with the available experimental values, and are as follows: WF(6) (3.15 eV), ReF(6) (4.58 eV), OsF(6) (5.92 eV), IrF(6) (5.99 eV), PtF(6) (7.09 eV), and AuF(6) (8.20 eV). A wide range of density functional theory exchange-correlation functionals were also evaluated, and only three gave satisfactory results. The corresponding pentafluorides are extremely strong Lewis acids, with OsF(5), IrF(5), PtF(5), and AuF(5) significantly exceeding the acidity of SbF(5). The optimized geometries of the corresponding MF(7)(-) anions for W through Ir are classical MF(7)(-) anions with M-F bonds; however, for PtF(7)(-) and AuF(7)(-) non-classical anions were found with a very weak external F-F bond between an MF(6)(-) fragment and a fluorine atom. These two anions are text book examples for "superhalogens" and can serve as F atom sources under very mild conditions, explaining the ability of PtF(6) to convert NF(3) to NF(4)(+), ClF(5) to ClF(6)(+), and Xe to XeF(+) and why Bartlett failed to observe XePtF(6) as the reaction product of the PtF(6)/Xe reaction.

Evidence for nine new solution state silicate oligomers has been discovered by (29)Si NMR homonuclear correlation experiments of (29)Si-enriched samples. In addition to enhancing signal sensitivity, the isotopic enrichment increases the probability of the (29)Si-(29)Si two-bond scalar couplings that are necessary for the observation of internuclear correlations in 2-D experiments. The proposed assignments are validated by comparisons of experimental and simulated cross-peaks obtained with high digital resolution. The internuclear connectivity indicated by the NMR data suggests that several of these oligomers can have multiple stereoisomers, including conformers and/or diastereomers. The stabilities of these oligomers and their possible stereoisomers have been investigated by electronic structure calculations.