Hydrocarbon-Soluble, Isolable Ziegler-Type Ir(0)(n) Nanoparticle Catalysts Made from [(1,5-COD)Ir(mu-O2C8H15)](2) and 2-5 Equivalents of AlEt3: Their High Catalytic Activity, Long Lifetime, and AlEt3-Dependent, Exceptional, 200 degrees C Thermal Stability

Hamdemir, Isil K.
Özkar, Saim
Yih, Kuang-Hway
Mondloch, Joseph E.
Finke, Richard G.
Hydrocarbon-solvent-soluble, isolable, Ziegler-type Ir(0)(n) nanoparticle hydrogenation catalysts made from the crystallo-graphically characterized [(1,5-COD)Ir(mu-O2C8H15)](2) precatalyst and 2-5 equiv of AlEt3 (>= 2 equiv of AlEt3 being required for the best catalysis and stability, vide infra) are scrutinized for their catalytic properties of (1) their isolability and then redispersibility without visible formation of bulk metal; (2) their initial catalytic activity of the isolated nanoparticle catalyst redispersed in cydohexane; (3) their catalytic lifetime in terms of total turnovers (TTOs) of cyclohexene hydrogenation; and then also and unusually (4) their relative thermal stability in hydrocarbon solution at 200 degrees C for 30 min. These studies are of interest since Ir(0)(n) nanoparticles are the currently best-characterized example, and a model/analogue, of industrial Ziegler-type hydrogenation catalysts made, for example, from Co(O2CR)(2) and >= 2 equiv of AlEt3. Eight important insights result from the present studies, the highlights of which are that Ir(0)(n) Ziegler-type nanoparticles, made from [(1,5-COD)Ir(mu-O2C8H15)](2) and AlEt3, are (i) quite catalytically active and long-lived; (ii) thermally unusually stable nanoparticle catalysts at 200 degrees C, vide infra, a stability which requires the addition of at least 3 equiv of AlEt3 (Al/Ir = 3), but where (iii) the Al/Ir = 5 Ir(0)(n) nanopartides are even more stable, for >= 30 mm at 200 degrees C, and exhibit 100 000 TTOs of cyclohexene hydrogenation. The results also reveal that (iv) the observed nanoparticle catalyst stability at 200 degrees C appears to surpass that of any other demonstrated nanoparticle catalyst in the literature, those reports being limited to <= 130-160 degrees C temperatures; and reveal that (v) AlEt3, or possibly surface derivatives of AlEt3, along with [RCO2 center dot AlEt3](-) formed from the first equiv of AlEt3 per 1/2 equiv of [(1,5-COD)Ir(mu-O2C8H15)](2) are main components of the nanoparticle stabilizer system, consistent with previous suggestions from Shmidt, Goulon, Bonnemann, and others. The results therefore also (vi) imply that either (a) a still poorly understood mode of nanoparticle stabilization by alkyl Lewis acids such as AlEt3 is present or, (b) that reactions between the Ir(0)(n) and AlEt3 occur to give initially surface species such as (Ir-surface)(x)-Et plus (Ir-srface)(x)-Al(Et)(2)Ir, where the number of surface Ir atoms involved, x = 1-4; and (vii) confirm the literature's suggestion that the activity of Ziegler-type hydrogenation can be tuned by the Al/Ir ratio. Finally and perhaps most importantly, the results herein along with recent literature make apparent (viii) that isolable, hydrocarbon soluble, Lewis-acid containing, Ziegler-type nanoparticles are an underexploited, still not well understood type of high catalytic activity, long lifetime, and unusually if not unprecedentedly high thermal stability nanoparticles for exploitation in catalysis or other applications where their unusual hydrocarbon solubility and thermal stability might be advantageous.


Verbascum eskisehirensis sp nov (Scrophulariaceae) from central Anatolia, Turkey
Karaveliogullari, Faik Ahmet; Ocak, Atilla; EKİCİ, MURAT; Cabi, Evren (Wiley, 2009-01-01)
Verbascum eskisehirensis Karavel., Ocak & Ekici sp. nov. (sect. Bothrosperma Murb.) is described and illustrated from Turkey. This new species is confined to B3 Eskisehir in central Anatolia. A morphological comparison is made with the closely related species; V. oreophilum K. Koch and V. pyramidatum M. Bieb. In addition, a cluster analysis was conducted and a distribution map of the new species and the related species is also given.
Seasonal variability of the Caspian Sea three-dimensional circulation, sea level and air-sea interaction
Ibrayev, R. A; Ozsoy, E; Schrum, C.; Sur, H. I. (Copernicus GmbH, 2010-3-3)
<jats:p>Abstract. A three-dimensional primitive equation model including sea ice thermodynamics and air-sea interaction is used to study seasonal circulation and water mass variability in the Caspian Sea under the influence of realistic mass, momentum and heat fluxes. River discharges, precipitation, radiation and wind stress are seasonally specified in the model, based on available data sets. The evaporation rate, sensible and latent heat fluxes at the sea surface are computed interactively through an atmo...
Mericarp micromorphology and anatomy of Salvia hedgeana Donmez, S. huberi Hedge and S. rosifolia Sm. (section Salvia Hedge, Lamiaceae)
Mericarp (nutlet) micromorphology and pericarp structure of three morphologically similar endemic Salvia species; Salvia hedgeana, S. huberi and S. rosifolia were investigated using LM, SEM and TEM. Salvia hedgeana has larger mericarps and abscission scars than S. huberi and S. rosifolia. Mericarp length to width ratio ranges from 1.11 in S. hedgeana to 1.60 in S. huberi. Mericarp shape is mainly ovoid, rarely broadly ovoid in S. hedgeana, and oblong in S. huberi. The mericarp surface sculpturing pattern in...
Covalent immobilization of alpha-amylase onto poly(2-hydroxyethyl methacrylate) and poly(styrene-2-hydroxyethyl methacrylate) microspheres and the effect of Ca2+ ions on the enzyme activity
Tumturk, H; Aksoy, S; Hasırcı, Nesrin (2000-02-01)
alpha-Amylase (1,4-alpha-D-glucan-glucanohydrolase; EC, Type VI-B from porcine pancreas, extra pure 29 units mg(-1)) was covalently immobilized on poly (2-hydroxyethyl methacrylate), p(HEMA), and poly (styrene-2-hydroxyethyl methacrylate), p(St-HEMA) microspheres, which were activated by using epichlorohydrin (ECH). The properties of the immobilized enzyme were investigated and compared with those of the free enzyme. For the assays carried out at 25 degrees C and pH 6.9, the relative activities were...
Tanyeli, Cihangir(2017-12-31)
Citation Formats
I. K. Hamdemir, S. Özkar, K.-H. Yih, J. E. Mondloch, and R. G. Finke, “Hydrocarbon-Soluble, Isolable Ziegler-Type Ir(0)(n) Nanoparticle Catalysts Made from [(1,5-COD)Ir(mu-O2C8H15)](2) and 2-5 Equivalents of AlEt3: Their High Catalytic Activity, Long Lifetime, and AlEt3-Dependent, Exceptional, 200 degrees C Thermal Stability,” ACS CATALYSIS, pp. 632–641, 2012, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/42121.