Ernestine W. Hill
ExxonMobil
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Featured researches published by Ernestine W. Hill.
Journal of Molecular Catalysis | 1987
John S. Bradley; Ernestine W. Hill; Michael E. Leonowicz; Horst Witzke
Abstract Metal cluster molecules containing easily displaceable ligands have been successfully exploited in organometallic cluster synthesis and to a lesser extent in homogeneous catalysis. We have extended this concept to elemental metal clusters in a fluid medium, by stabilizing colloidal transition metal particles in non-polar hydrocarbon solutions using polymers as tenuous ligands to prevent aggregation of the metal. The colloids were prepared by condensation of the metal vapor into a cold solution of the stabilizing polymer. In the absence of polymer, the metal atoms agglomerate into
Journal of Catalysis | 1991
John S. Bradley; John M. Millar; Ernestine W. Hill; Sutinder Behal
100 μm aggregates of microcrystalline metal, containing crystallites of the order of 20–50 A in diameter. In the presence of polymer, agglomeration of the metal proceeds only to the 20–50 A stage, at which point the polymer sterically stabilizes the metal cluster and prevents further aggregation. The colloidal solutions thus obtained exhibit considerable thermal stability. The homogeneous catalytic properties of these solutions have been investigated in the hydrogenation of acenaphthylene. Colloidal metals prepared in this way also serve as sources of heterogeneous metal catalysts; copper-nickel colloids have been used in this way to probe the particle size dependency of filamentous carbon formation from ethane.
Journal of Organometallic Chemistry | 1980
John S. Bradley; Gerald B. Ansell; Ernestine W. Hill
Highly dispersed (<10{angstrom}) platinum has been prepared in colloidal solution by condensing platinum vapor into a solution of triisobutylaluminoxane in methylcyclohexane. Carbon monoxide, adsorbed in a linear mode on the surface of the colloidal metal, has been characterized by infrared spectroscopy and {sup 13}C NMR. The chemical shift of the adsorbed CO is 192 ppm, and the absence of a Knight shift is interpreted in terms of a pseudomolecular description of the highly dispersed platinum particles, which are not large enough to exhibit metallic properties. The CO covered colloid is converted by hydrolysis into the molecular platinum carbonyl anion clusters (Pt{sub 3}(CO){sub 6}){sub n}{sup 2 {minus}}, n = 3, 4.
Studies in Surface Science and Catalysis | 1993
J.S. Bradley; J.M. Millar; Ernestine W. Hill; C. Klein; Bruno Chaudret; A. Duteuil
Abstract Ru 6 C(CO) 16 2- is produced in reproducibly high yield by the reduction of Ru 3 12 with Mn(CO) 5 in refluxing diglyme. 13 C NMR evidence identifies carbon monoxide as the source of the encapsulated carbon atom. The facile prototype synthesis of an organometallic derivative of the Ru 6 C core is described.
Polyhedron | 1990
John S. Bradley; Suzanne Harris; Ernestine W. Hill; Michelle A. Modrick
Abstract The adsorption of carbon monoxide on colloidal solutions of nanosize particles of palladium and palladium-copper alloys is reported. Partial coverage spectra of adsorbed CO on a palladium colloid show similarity with those for CO on single crystal and supported palladium with the development of first triply bridged CO, then doubly bridged CO which dominates the spectrum to higher coverages, and linear CO which appears at the highest coverages. Addition of a second metal, copper, to the palladium surface perturbs the spectrum of adsorbed CO in a manner consistent with a simple dilution effect. Liquid phase 13C NMR shows that the adsorption-desorption exchange reaction of CO in the presence of the palladium-copper alloy is faster than for the pure palladium.
Journal of The Chemical Society-dalton Transactions | 1997
John S. Bradley; Suzanne Harris; Ernestine W. Hill
Abstract The syntheses, crystal structures and electronic structures of the new μ4-vinylidene clusters, Fe4(CO)12(CC(OCH3)2) and Fe4(CO)12(CC(OCH3)CH3), are reported. Fe4(CO)12(CC(OCH3)2) was prepared by the methylation of [Fe4(CO)12(CCO2CH3)]− with trimethyloxonium fluoroborate in methylene chloride at 25°C. Fe4(CO)12(CC(OCH3)CH3) was prepared in an analogous manner from [Fe4(CO)12(CC(O)CH3)]−. Fe4(CO)12(CC(OCH3)2) crystallizes in the monoclinic space group P21/c (C2h5 No. 14) with a = 13.900(2), b = 8.909(2), c = 17.116(4) A, β = 94.59(2)°; pcalc = 2.03 g cm−3 for mol. wt 645.6 and Z = 4. Fe4(CO)12(CC(OCH3)CH3) crystallizes in the monoclinic space group P21/c (C2h5 No. 14) with a = 28.441(6), b = 9.204(2), c = 17.466(4) A, β = 108.51(2)°; pcalc = 1.93 g cm−3 for mol. wt = 629.6 and Z = 8. Both clusters have an open butterfly core of four iron atoms with the vinylidene ligand bound to all four metal atoms. Molecular orbital calculations using the Fenske—Hall method were carried out for the two clusters. The molecular and electronic structures of the molecules are compared with each other and with those of μ4-methylidyne clusters. Although both of these clusters contain a formal CC double bond in the vinylidene ligand, the presence of oxygen atoms in these ligands leads to a delocalized π system and only partial double bond character in this CC bond. Changes in the structure of the cluster framework can be correlated with the oxygen content and thus double bond character in the vinylidene ligand.
Journal of The Chemical Society, Chemical Communications | 1990
John S. Bradley; John R. A. Millar; Ernestine W. Hill; Michael T. Melchior
The µ 4 -vinylidene cluster Fe 4 (CO) 12 (µ 4 -η 2 -C CHCH 3 ) has been prepared by the sequential reaction of Fe 4 (CO) 12 [CC(CH 3 )(OCH 3 )], with lithium triethylhydroborate and trimethylsilyl trifluoromethanesulfonate. The cluster has an open butterfly arrangement of four iron atoms with the prop-1-ene-1,1-diyl ligand bound to all four iron atoms in a manner giving an axial CC bond, perpendicular to both the mutually perpendicular Fe–Fe vectors between the wingtip iron atoms (Fe w ) and between the hinge iron atoms (Fe h ). The vinylidene carbon atom lies below the Fe w –Fe w vector, essentially inside the Fe 4 core. Molecular orbital calculations using the Fenske–Hall method were carried out for the cluster, showing that the geometry of the Fe 4 CCHCH 3 fragment results from overlap between the formal CC double bond and the two Fe w iron atoms. Comparisons are drawn between Fe 4 (CO) 12 (µ 4 -η 2 -C CHCH 3 ) and other Fe 4 vinylidene clusters.
Chemistry of Materials | 1993
John S. Bradley; Ernestine W. Hill; Carl Klein; Bruno Chaudret; Anne Duteil
Carbon monoxide adsorbed on a stabilized 20 A palladium colloid in methylcyclohexane has been characterised by solution IR and high resolution NMR spectroscopy.
Chemistry of Materials | 1992
John S. Bradley; Ernestine W. Hill; S. Behal; C. Klein; Anne Duteil; Bruno Chaudret
Journal of the American Chemical Society | 1979
John S. Bradley; Gerald B. Ansell; Ernestine W. Hill