935-31-9Relevant academic research and scientific papers
A highly stable adamantyl-substituted pincer-ligated iridium catalyst for alkane dehydrogenation
Punji, Benudhar,Emge, Thomas J.,Goldman, Alan S.
, p. 2702 - 2709 (2010)
The adamantyl-substituted pincer-ligand precursor AdPCP-H [(AdPCP = κ3-C6H3-2,6-(CH 2PAd2)2); Ad = 1-adamantyl] has been synthesized by the reaction of 1,3-dibromoxylene with di-1-adamantylphosphine in the presence of triethylamine. Treatment of AdPCP-H with [Ir(COD)Cl]2 (COD = 1,5-cyclooctadiene) affords the pincer-ligated complex (AdPCP)IrHCl, which was crystallographically characterized. Dehydrohalogenation of (AdPCP)IrHCl either with LiBEt3H or with KOtBu, under hydrogen atmosphere, yields the hydrides ( AdPCP)IrH2 and (AdPCP)IrH4. ( AdPCP)IrH2 catalyzes dehydrogenation of alkanes with a level of activity comparable to that of the previously reported ( tBuPCP)IrH2, while it is thermally much more robust than the tBuPCP analogue, as well as iPrPCP or tBuPOCOP pincer complexes.
Acceptorless alkane dehydrogenation catalyzed by iridium CCC-pincer complexes
Chianese, Anthony R.,Drance, Myles J.,Jensen, Kelsey H.,McCollom, Samuel P.,Yusufova, Nevin,Shaner, Sarah E.,Shopov, Dimitar Y.,Tendler, Jennifer A.
, p. 457 - 464 (2014/02/14)
Iridium complexes of CCC-pincer bis-N-heterocyclic carbenes, including a newly synthesized trifluoromethyl-substituted complex, were examined as catalysts for the acceptorless dehydrogenation of cyclooctane and n-undecane. Up to 103 turnovers were observed for the dehydrogenation of cyclooctane, and up to 97 turnovers were observed for the dehydrogenation of n-undecane. The catalysts showed high initial turnover frequencies, followed by a gradual loss of activity over 24 h. Experiments indicate that this loss of activity is due to catalyst decomposition rather than product inhibition. Stoichiometric reactivity was investigated for the precatalysts, focusing on the synthesis of dihydride and trihydride complexes as well as the dissociation and addition of neutral ligands.
Investigation of iridium CF3PCP pincer catalytic dehydrogenation and decarbonylation chemistry
Adams, Jeramie J.,Arulsamy, Navamoney,Roddick, Dean M.
experimental part, p. 1439 - 1447 (2012/04/10)
The iridium fluorinated pincer complex (CF3PCP)Ir(cod) (CF 3PCP = 2,6-C6H3(CH2P(CF 3)2)2) catalyzes hydrogen transfer from cyclooctane (coa) to tert-butylethylene (tbe) in 1/1 coa/tbe at 200 °C to give cyclooctene (coe) and neohexane (tba) at an initial rate of 40 TO h -1. In 5/1 coa/tbe, higher initial activity (155 TO h-1) and higher turnovers (2580 TON's after 1450 min) are found. Samples of 95% tbe contain significant amounts of isoprene (2-methyl-1,3-butadiene), which reacts with (CF3PCP)Ir(cod) to initially form (CF3PCP) Ir(isoprene). Alkene inhibition studies show that (CF3PCP)Ir is only modestly inhibited (67% reduced initial activity) in the presence of 800 equiv of added coe. Unlike donor pincer systems, no decrease in activity is noted under 1 atm of N2 or in the presence of excess water. Hydrogenation of (CF3PCP)Ir(L) (L = cod, isoprene) did not produce (CF 3PCP)Ir(H)x but instead afforded the first example of the unusual aryl-bridged bimetallic complex [(μ-1κ2(P,C), 2κ2(P′,C)-CF3PCP)Ir(H)2] 2(μ-CF3PCPH)(μ-H), which has been isolated and crystallographically characterized. Ir(I) pincer complexes (CF 3PCP)Ir(L) (L = MeP(C2F5)2, CO, dfepe (dfepe = (C2F5)2PCH2CH 2P(C2F5)2)) also serve as moderately active aldehyde decarbonylation catalyst precursors for 2-naphthaldehyde with similar activities in diglyme (1.7 TO h-1, 152 °C) and in 1,4-dioxane (0.052 TO h-1, 94 °C). The catalyst resting states are the corresponding five-coordinate carbonyl complexes (CF3PCP) Ir(MeP(C2F5)2)(CO), (CF3PCP)Ir(CO) 2, and [(CF3PCP)Ir(CO)]2(μ-dfepe). DFT studies indicate that the preferred catalyst resting state for alkane dehydrogenation, (CF3PCP)Ir(cod), can be ascribed to the lower steric requirements of the CF3-substituted pincer ligand.
Efficient thermochemical alkane dehydrogenation and isomerization catalyzed by an iridium pincer complex
Liu, Fuchen,Goldman, Alan S.
, p. 655 - 656 (2007/10/03)
((i-Pr)PCP)IrH2 is found to be a remarkably effective solution-phase catalyst for the 'acceptorless' thermochemical dehydrogenation of cycloalkanes (and isomerization in the case of cyclodecane), and the first such catalyst reported to effect the dehydrogenation of n-alkanes.
Thermochemical alkane dehydrogenation catalyzed in solution without the use of a hydrogen acceptor
Xu, Wei-Wei,Rosini, Glen P.,Gupta, Mukta,Jensen, Craig M.,Kaska, William C.,Krogh-Jespersen, Karsten,Goldman, Alan S.
, p. 2273 - 2274 (2007/10/03)
(PCP)IrH2 [PCP = η3-C6H3(PBut2) 2-1,3] catalyzes the efficient (several hundred mol product/mol catalyst) dehydrogenation of alkanes under reflux to give the corresponding alkenes and dihydrogen.
Alkenes from Cyclic Sulfates and Thionocarbonates of 1,2-Diols via Tellurium Chemistry
Chao, Bin,McNulty, Kenneth C.,Dittmer, Donald C.
, p. 7209 - 7212 (2007/10/02)
Treatment of 1,2-diol cyclic sulfates (1,3,2-dioxathiolane 2,2-dioxides) with telluride ion, generated in situ by reduction of the element, yields alkenes rapidly (10 min - 2 h) under mild conditions (0 deg C to room temperature).The reaction is stereospecific, e. g. meso-2,3-diphenylethane-2,3-diol -> cis-stilbene; d,l-2,3-diphenylethane-2,3-diol -> trans-stilbene.Unsaturated mannose and ribose derivatives have been obtained, and diethyl (-)-tartrate gives diethyl fumarate.The reaction may be performed with 0,1 equiv or less of elemental tellurium in the presence of a stoichiometric amount of reducing agent.Reaction of telluride ion with cyclic thionocarbonates (1,3-dioxolane-2-thiones) of meso- and d,l-1,2-diphenylethane-1,2-diol yields cis- and trans-stilbene, respectively.
Stereoselective synthesis of vicinal dilithioalkenes by addition of lithium metal, to carbon-carbon triple bonds
Maercker,Girreser
, p. 8019 - 8034 (2007/10/02)
The reaction of various cyclic and acyclic alkynes with lithium dust (2% sodium) to form vicinal dilithioalkenes has been investigated. Aliphatic alkynes, e.g. 3-hexyne (27a), exclusively afford the corresponding (E)-dilithioalkenes, insoluble solids which are stable at room temperature and allow access to a variety of tetrasubstituted olefins in acceptable yields.
β'β ANIONIC ELIMINATION OF CARBOXYLIC ESTERS
Aubert, Corinne,Begue, Jean-Pierre,Biellmann, Jean-Francois
, p. 5581 - 5590 (2007/10/02)
The elimination of lithium, magnesium and aluminium enolates of isobutyrates of medium ring cyclanols occurs in a syn fashion.A set of experimental procedures is presented.This elimination seems to be restricted to strained systems.The stereochemistry has been determined on stereospecifically deuterated cyclooctanol isobutyrates.The primary isotope effect kH/k2 was 3.0 +/- 0.1 and the secondary 1.1.The name β'β elimination is proposed for this syn elimination and related elimination.
Diphenylphosphinated Ethylene Oligomers as polymeric Reagents for Synthesis of Alkyl Chlorides from Alcohols
Bergbreiter, David E.,Blanton, James R.
, p. 337 - 338 (2007/10/02)
Diphenylphosphinated ethylene oligomers can be used as homogeneous polymeric reagents at 90 deg C in carbon tetrachloride to form alkyl chlorides from alcohols and since these funcionalized ethylene oligomers precipitate quantitatively from solution at 25 deg C, they can be easily recovered and separated from the reaction products and can be partially recycled.
