F:Flammable;
75-83-2Relevant articles and documents
Mechanistic Studies of the Reactions of 3,3-Dimethylbut-1-ene with Deuterium over Supported-metal Catalysts
Brown, Ronald,Kemball, Charles
, p. 2519 - 2526 (1993)
The reactions of 3,3-dimethylbut-1-ene with deuterium have been followed over a number of silica-supported metal catalysts at 254 K and the products analysed by mass spectrometry (MS) and deuterium NMR spectroscopy.The main reaction was the formation of the alkane, 2,2-dimethylbutane, in which extensive redistribution of H and D atoms had occurred in the ethyl group.It was possible to make a complete analysis of all 12 isotopic alkanes, i.e. (CH3)3CCX2CX3 where X represents H or D, in the products formed over supported Pd and Rh using both the NMR and MS results.Relatively little exchange of alkene occurred but it was most noticeable over Pd/SiO2.The results were interpreted in terms of a mechanistic model involving three types of adsorbed species: alkene, 1-alkyl and 2-alkyl.Any adsorbed alkene may either be desorbed or form one of the alkyls, both alkyls may either be desorbed as alkane product or revert to alkene.By choosing suitable parameters and solving 23 simultaneous equations, it was possible to obtain calculated distributions for the 12 isotopic products in good agreement with the experimental results.The presence of the tertiary butyl group has an influence on the relative stability of the adsorbed intermediates and also on the relative ease of activation (addition or removal) of primary and secondary H or D atoms.
Synthesis of a 14-electron iridium(III) complex with a xanthene-based bis(silyl) chelate ligand (xantsil): A distorted seesaw-shaped fourcoordinate geometry and reactions leading to 16-electron complexes
Komuro, Takashi,Furuyama, Keisuke,Kitano, Takeo,Tobita, Hiromi
, p. 686 - 694 (2014)
Synthesis, structure determination, and reactions of a 14-electron four-coordinate iridium(III) complex bearing a xanthene-based bis(silyl) chelate ligand, i.e., Ir{κ2(Si,Si)-xantsil}(PCy3)Cl (1a, xantsil = (9,9-dimethylxanthene-4,5-diyl)bis(dimethylsilyl)), are reported. A precursor of 1a, the 16-electron (dihydrido)iridium(V) complex Ir{κ2 (Si,Si)-xantsil}(H)2(PCy3)Cl (2), was prepared by the reaction of [IrCl-(coe)2]2 (coe = cyclooctene) with 4,5-bis(dimethylsilyl)-9,9-dimethylxanthene (xantsilH2) and PCy 3. Dehydrogenation reaction of 2 with 3,3-dimethylbut-1-ene, a hydrogen acceptor, afforded a mixture of 1a and its isomer 1b, abbreviated as 1a + 1b, together with 2,2-dimethylbutane. Single crystals obtained from a CH 2Cl2 solution of 1a + 1b contained only isomer 1a. X-ray crystal structure analysis of one of the crystals revealed that 1a adopts a distorted seesaw-shaped four-coordinate geometry where the coordinatively unsaturated metal center is stabilized by weak agostic interaction of two γ-C-H bonds of the PCy3 ligand. On the other hand, NMR spectroscopic analysis of 1a + 1b demonstrated that 1a is in fast equilibrium with a minor amount of 1b in solution. Replacement of the chloro ligand in complexes 1a + 1b by a triflato ligand with AgOTf (OTf = OSO2CF 3) afforded quantitatively a single product, i.e., the 16-electron iridiumetriflato complex Ir{κ3(Si,O,Si)-xantsil}(PCy 3)(OTf) (3). 1a + 1b and 16-electron complex 2 are interconvertible via oxidative addition of dihydrogen (from 1a + 1b to 2) and alkene hydrogenation (from 2 to 1a + 1b). Complexes 1a + 1b and 2 were found to catalyze hydrogenation of 3,3-dimethylbut-1-ene.
Formation of a C-C double bond from two aliphatic carbons. Multiple C-H activations in an iridium pincer complex
Polukeev, Alexey V.,Marcos, Rocío,Ahlquist, M?rten S. G.,Wendt, Ola F.
, p. 2060 - 2067 (2015)
The search for novel, atom-economic methods for the formation of C-C bonds is of crucial importance in synthetic chemistry. Especially attractive are reactions where C-C bonds are formed through C-H activation, but the coupling of unactivated, alkane-type Csp3-H bonds remains an unsolved challenge. Here, we report iridium-mediated intramolecular coupling reactions involving up to four unactivated Csp3-H bonds to give carbon-carbon double bonds under the extrusion of dihydrogen. The reaction described herein is completely reversible and the direction can be controlled by altering the reaction conditions. With a hydrogen acceptor present a C-C double bond is formed, while reacting under dihydrogen pressure leads to the reverse process, with some of the steps representing net Csp3-Csp3 bond cleavage. Mechanistic investigations revealed a conceptually-novel overall reactivity pattern where insertion or deinsertion of an Ir carbene moiety, formed via double C-H activation, into an Ir-C bond is responsible for the key C-C bond formation and cleavage steps.
Hydroformylation of olefins catalyzed by alkene complexes of platinum(0)
Botteghi, Carlo,Paganelli, Stefano
, p. C41 - C45 (1991)
In the presence of methanesulfonic acid the platinum(0) complex catalyses the hydroformylation of various olefins.In some cases there is quite good chemoselectivity and high regioselectivity towards n-aldehyde.
Synthesis of A Pincer-IrV Complex with A Base-Free Alumanyl Ligand and Its Application toward the Dehydrogenation of Alkanes
Morisako, Shogo,Watanabe, Seiya,Ikemoto, Satoru,Muratsugu, Satoshi,Tada, Mizuki,Yamashita, Makoto
, p. 15031 - 15035 (2019)
A pincer-iridium complex bearing a Lewis-base-free X-type alumanyl ligand has been synthesized. X-ray diffraction, NMR and IR spectroscopy, as well as XANES analysis confirmed its tetrahydrido-IrV structure and Lewis acidity at the Al center as supported by DFT calculations. The resulting complex was applied as a catalyst for the transfer dehydrogenation of cyclooctane.
Boosting homogeneous chemoselective hydrogenation of olefins mediated by a bis(silylenyl)terphenyl-nickel(0) pre-catalyst
Lücke, Marcel-Philip,Yao, Shenglai,Driess, Matthias
, p. 2909 - 2915 (2021/03/14)
The isolable chelating bis(N-heterocyclic silylenyl)-substituted terphenyl ligand [SiII(Terp)SiII] as well as its bis(phosphine) analogue [PIII(Terp)PIII] have been synthesised and fully characterised. Their reaction with Ni(cod)2(cod = cycloocta-1,5-diene) affords the corresponding 16 VE nickel(0) complexes with an intramolecularη2-arene coordination of Ni, [E(Terp)E]Ni(η2-arene) (E = PIII, SiII; arene = phenylene spacer). Due to a strong cooperativity of the Si and Ni sites in H2activation and H atom transfer, [SiII(Terp)SiII]Ni(η2-arene) mediates very effectively and chemoselectively the homogeneously catalysed hydrogenation of olefins bearing functional groups at 1 bar H2pressure and room temperature; in contrast, the bis(phosphine) analogous complex shows only poor activity. Catalytic and stoichiometric experiments revealed the important role of the η2-coordination of the Ni(0) site by the intramolecular phenylene with respect to the hydrogenation activity of [SiII(Terp)SiII]Ni(η2-arene). The mechanism has been established by kinetic measurements, including kinetic isotope effect (KIE) and Hammet-plot correlation. With this system, the currently highest performance of a homogeneous nickel-based hydrogenation catalyst of olefins (TON = 9800, TOF = 6800 h?1) could be realised.
Photo-Initiated Cobalt-Catalyzed Radical Olefin Hydrogenation
Sang, Sier,Unruh, Tobias,Demeshko, Serhiy,Domenianni, Luis I.,van Leest, Nicolaas P.,Marquetand, Philipp,Schneck, Felix,Würtele, Christian,de Zwart, Felix J.,de Bruin, Bas,González, Leticia,V?hringer, Peter,Schneider, Sven
, p. 16978 - 16989 (2021/08/09)
Outer-sphere radical hydrogenation of olefins proceeds via stepwise hydrogen atom transfer (HAT) from transition metal hydride species to the substrate. Typical catalysts exhibit M?H bonds that are either too weak to efficiently activate H2 or too strong to reduce unactivated olefins. This contribution evaluates an alternative approach, that starts from a square-planar cobalt(II) hydride complex. Photoactivation results in Co?H bond homolysis. The three-coordinate cobalt(I) photoproduct binds H2 to give a dihydrogen complex, which is a strong hydrogen atom donor, enabling the stepwise hydrogenation of both styrenes and unactivated aliphatic olefins with H2 via HAT.
Synthesis and reactivity of nitridorhenium complexes incorporating the mercaptoethylsulfide (SSS) ligand
Ison, Elon A.,Lambic, Nikola S.,Sommer, Roger D.
, p. 6127 - 6134 (2020/05/25)
A method for the preparation of nitridorhenium(v) complexes of the form (SSS)Re(N)(L) (where SSS = 2-mercaptoethylsulfide and L = PPh3andt-BuNC) has been described. These complexes react with Lewis acids allowing for the isolation of adducts. The lack of a significant steric profile on the SSS ligand combined with enhanced nucleophilicity of the nitrido group does not allow for the effective formation of frustrated Lewis pairs with these complexes and as a result these species are poor catalysts for the hydrogenation of unactivated olefins.
Highly Active Superbulky Alkaline Earth Metal Amide Catalysts for Hydrogenation of Challenging Alkenes and Aromatic Rings
Eyselein, Jonathan,F?rber, Christian,Grams, Samuel,Harder, Sjoerd,Knüpfer, Christian,Langer, Jens,Martin, Johannes,Thum, Katharina,Wiesinger, Michael
supporting information, p. 9102 - 9112 (2020/03/30)
Two series of bulky alkaline earth (Ae) metal amide complexes have been prepared: Ae[N(TRIP)2]2 (1-Ae) and Ae[N(TRIP)(DIPP)]2 (2-Ae) (Ae=Mg, Ca, Sr, Ba; TRIP=SiiPr3, DIPP=2,6-diisopropylphenyl). While monomeric 1-Ca was already known, the new complexes have been structurally characterized. Monomers 1-Ae are highly linear while the monomers 2-Ae are slightly bent. The bulkier amide complexes 1-Ae are by far the most active catalysts in alkene hydrogenation with activities increasing from Mg to Ba. Catalyst 1-Ba can reduce internal alkenes like cyclohexene or 3-hexene and highly challenging substrates like 1-Me-cyclohexene or tetraphenylethylene. It is also active in arene hydrogenation reducing anthracene and naphthalene (even when substituted with an alkyl) as well as biphenyl. Benzene could be reduced to cyclohexane but full conversion was not reached. The first step in catalytic hydrogenation is formation of an (amide)AeH species, which can form larger aggregates. Increasing the bulk of the amide ligand decreases aggregate size but it is unclear what the true catalyst(s) is (are). DFT calculations suggest that amide bulk also has a noticeable influence on the thermodynamics for formation of the (amide)AeH species. Complex 1-Ba is currently the most powerful Ae metal hydrogenation catalyst. Due to tremendously increased activities in comparison to those of previously reported catalysts, the substrate scope in hydrogenation catalysis could be extended to challenging multi-substituted unactivated alkenes and even to arenes among which benzene.
Zero valent iron complexes as base partners in frustrated Lewis pair chemistry
Fraser, Craig,Tinnermann, Hendrik,Young, Rowan D.
supporting information, p. 15184 - 15189 (2020/11/18)
The prototypical iron(0) complex [Fe(CO)3(PMe3)2] (1) forms a frustrated Lewis pair (FLP) with B(C6F5)3 (BCF). In this FLP, the iron complex acts as the Lewis base partner, and the borane as the Lewis acid partner. This FLP is able to cleave H-H, H-Cl, H-O and H-S bonds in H2, HCl, H2O and HSPh. The FLP 1/BCF is shown to catalyze the hydrogenation of alkenes under mild conditions, where terminal alkenes are preferentially reduced. Mechanistic studies using D2 gas suggest that a branched intermediate in an alkene insertion cycle or an ionic cycle is favored for this catalytic reaction.
