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Title
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THE THERMAL AND PHOTOCHEMICAL BEHAVIOR OF RUTHENIUM DODECACARBONYL, RU-3(CO)-12, SUPPORTED ON POROUS VYCOR GLASS (CATALYSIS).
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Identifier
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AAI8601634
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identifier
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8601634
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Creator
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DIETER, THOMAS.
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Contributor
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Harry D. Gafney
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Date
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1985
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Language
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English
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Publisher
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City University of New York.
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Subject
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Chemistry, Inorganic
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Abstract
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Ru(CO)(,5) and Ru(,3)(CO)(,12) adsorb onto Corning's code 7930 porous Vycor glass, PVG, without a change in their spectral properties, measured by optical transmission spectroscopy and diffuse reflec- tance FTIR spectroscopy (DRIFT). Adsorbed Ru(,3)(CO)(,12) under CO is stable towards photoinitiated decomposition to Ru(CO)(,5). Thermal or photochemical activation of the initially physisorbed cluster causes evolution of CO and leads to the chemisorbed species HRu(,3)(CO)(,10)- (OSi ), identified by its optical and vibrational spectrum. The energy of activation for this process is 6.2 (+OR-) 0.3 kcal/mol. Under carbon monoxide the chemisorption is reversible, regenerating >90% of the physisorbed cluster. The energy of activation for the backreaction is 5.1 (+OR-) 0.2 kcal/mol.;From solution the sterically demanding substituted trimer Ru(,3)- (CO)(,9)(PPh(,3))(,3) does not adsorb onto PVG. Although the supported species can be obtained by co-sublimation of PPh(,3) and Ru(,3)(CO)(,12) it decomposes under vacuum at room temperature.;PVG supported Ru(,3)(CO)(,12) thermally decarbonylates in vacuum to yield CO-covered ruthenium crystallites. After thermal decomposition in the presence of oxygen CO-covered, partially oxidized ruthenium species are observed on the surface. Reduction of the oxidized metal under flowing H(,2) at 200(DEGREES)C and subsequent recarbonylation with CO yields a new IR band at 2031 cm('-1), assigned to agglomerated ruthenium metal.;The chemisorbed cluster HRu(,3)(CO)(,10)(OSi ) is a thermally and photochemically active catalyst for the isomerization of 1-pentene to cis- and trans-2-pentene with turnover numbers in excess of 400. Thermal catalysis initially yields cis- and trans-isomers in a ratio of ca. 1:1.2 before reaching the thermodynamic ratio of 1:3.2. The ratio of 2-pentene isomers produced by photoinitiated catalysis is in the order of 1:5 and constant over several cycles.;In fluid solution Ru(,3)(CO)(,12) photochemically reacts with L = 1-pentene, PPh(,3) and P(t-Bu)(,3) to form the substituted monomer Ru- (CO)(,4)L with limiting quantum yields of decomposition of 8.0 (+OR-) 0.7 x 10('-2), 5.7 (+OR-) 0.4 x 10('-2), and 8.4 (+OR-) 0.5 x 10('-2) respectively. The mono- substituted Ru(CO)(,4)PPh(,3) reacts with PPh(,3) to form Ru(CO)(,3)(PPh(,3))(,2) under photochemical conditions and with CO to regenerate ruthe- nium dodecacarbonyl in a thermal backreaction at room temperature. At temperatures above 30(DEGREES)C a thermal substitution of Ru(,3)(CO)(,12) with PPh(,3) leads to the substituted trimer Ru(,3)(CO)(,9)(PPh(,3))(,3). The activation energy of this reaction has been calculated to 24.2 (+OR-) 1.2 kcal/mol.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
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Program
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Chemistry
