563-78-0Relevant articles and documents
REACTIONS OF DIMETHYLBUTENES ON NICKEL-EXCHANGED AND ZINC-EXCHANGED 13X-TYPE ZEOLITES
Moller, Bernard W.,Kemball, Charles,Leach, H. Frank
, p. 453 - 466 (1983)
Reactions involving 3,3-dimethylbut-1-ene (I), 2,3-dimethylbut-1-ene (II) and 2,3-dimethylbut-2-ene (III), including isomerization and exchange with D2 or D2O, have been studied on zinc-exchanged and nickel-exchanged X-type zeolites.The effect of various pretreatments (with hydrogen, carbon monoxide or oxygen) was examined with NiX (21percent exchanged) which, unlike the ZnX zeolites, was a catalyst for the hydrogenation of the C6 alkenes.The acid-catalysed isomerization of I (to II and III) occured on both ZnX and NiX and the activity of the zeolites increased sharply with M2+ ion content.With ZnX(21) or NiX(21) inclusion of H2O or D2O (which gave exchanged products) in the reaction mixture enhanced the rate of isomerization of I, presumably by the creation of more Bronsted acidity.Hydrogenation activity was found only with NiX and was attributed to the reduction of some of the accessible Ni2+ ions by the alkene + hydrogen mixture to Ni+ or possibly Ni0.Treatment with carbon monoxide or oxygen demonstrated the dual-function behaviour of NiX(21), not influencing the acidic catalysis but inhibiting almost completely the hydrogenation activity.
Tautomerization of pyridine and 2-substituted pyridines to pyridylidene ligands by the iridium(I)-diene complex TpMe2Ir(η4- CH2=C(Me)C(Me)=CH2)
Vattier, Florencia,Salazar, Veronica,Paneque, Margarita,Poveda, Manuel L.,Alvarez, Eleuterio
, p. 498 - 510 (2014)
The complex TpMe2Ir(η4-CH2=C(Me)C(Me)= CH2) (3; TpMe2 = hydrotris(3,5-dimethylpyrazolyl)borate) reacts with pyridines NC5H4-2-R (R = H, Me, SiMe 3, F, OMe, NMe2, C(=O)Me) in cyclohexane, with formation of Ir(III) products whose natures depend strongly on the reaction conditions and on the R substituent. The simplest case is for R = NMe2, C(=O)Me, where κ2:σ2-but-2-enediyl N-H pyridylidenes, i.e. the result of the metal-promoted tautomerization of the pyridines, are the only species obtained from 60 to 150 C. For R = Me, F the N-bonded adducts TpMe2Ir(κ2-CH2C(Me)=C(Me)CH 2)(NC5H4-2-R) are formed at 60 C but, under harsher conditions (120-150 C), the observed products are, exclusively and respectively, the N-H pyridylidene and a bicyclic carbene compound derived from the formal, trans-stereospecific transfer of the N-H hydrogen of the corresponding (not observed) pyridylidene onto one of the carbons of the C=C double bond of the but-2-enediyl moiety, the other experiencing C-N formation. For R = OMe, the N adduct formed at 60 C transforms, at higher temperatures, into a mixture of the N-H pyridylidene and the bicyclic carbene, with no further evolution. More complex behavior is observed for the rest of the pyridines studied. Thus, when R = SiMe3, in addition to the expected N-H pyridylidene, two isomeric N-H pyridylidenes containing a κ2: σ2-but-1-enediyl coligand are also formed under kinetic control (60 C) but with both cleanly transforming into the former compound at higher temperatures. Finally, for R = H only the N adduct is formed under kinetic control at 25 C but this species transforms almost completely into a mixture of the N-H pyridylidene and two epimeric, N-C bicyclic carbenes after prolonged heating at 150 C. A detailed study of the temperature-dependent behavior of 3 in C6H6 has also been undertaken, revealing the interesting deuteration of its =CH2 termini by C6D6.
CATALYTIC PROPERTIES OF EIVB-SUBSTITUTED TUNGSTEN CARBONYL COMPLEXES (EIVB=Ge, Sn) IMMOBILIZED ON A SILICA SUPPORT
Linthoudt, J. P. van,Delmulle, L.,Kelen, G. P. van der
, p. 39 - 48 (1980)
The catalytic activity in olefin disproportionation of a 3,3-dimethyl-1-butene substrate has been investigated for a series of EIVB-W(CO)3C5H5 species (EIVB=Ge, Sn) chemically bonded to a high surface silica carrier.Different product distributions and conversion factors were obtained by thermal and UV activation of the catalysts, whereas variation of the EIVB element had little effect.In all cases, isomerization was observed rather than disproportionation, probably because of steric interaction between the rather bulky t-Bu groups at the active W sites.
The methylation of alkenes to triptyls with dimethyl carbonate
Armitage, Gareth G.,Bonati, Matteo L. M.,Guo, Neng,Gaemers, Sander,Shabaker, John W.
, p. 370 - 374 (2013)
A series of methylating reagents: methanol, dimethylether and dimethylcarbonate, have been evaluated for their ability to methylate 2,3-dimethylbut-2-ene to yield triptyls (a mixture of triptane and triptene). The results presented highlight that dimethylcarbonate is a far superior methylating agent compared to methanol or dimethylether, providing a higher yield of triptyls.
Solid-State 1H MAS NMR Study on the Highly Active Protons in Partially Reduced Ag3PW12O40
Baba, Toshihide,Nomura, Mamoru,Ono, Yoshio,Ohno, Yo-ichi
, p. 12888 - 12893 (1993)
The physicochemical nature of protons generated by the partial reduction of Ag+ cations in Ag3PW12O40 with hydrogen was investigated by means of 1H MAS NMR.When Ag3PW12O40 was partially reduced with hydrogen, the 1H MAS NMR spectrum demonstrated the generation of two kinds of acidic protons, which are observed at 6.4 and 9.3 ppm.The protons at 6.4 ppm exist only in the presence of hydrogen in the gas phase.The amount of these protons reversibly changes with the hydrogen pressure.In contrast, the amount of protons at 9.3 ppm is independent of the hydrogen pressure.The amount of protons at 6.4 and 9.3 ppm depended on the degree of the reduction of Ag+ cations in Ag3PW12O40.When the degree of the reduction of Ag+ was 13 percent, the protons at 6.4 ppm were mainly observed and the protons at 9.3 ppm were only slightly observed.The amount of protons at 6.4 ppm increased by increasing the degree of the reduction of Ag+ cations from 13 percent to 32 percent.These protons were scarcely observed when the degree of reduction of Ag+ cations reached 67 percent.In contrast, the amount of protons at 9.3 ppm increased by increasing the degree of reduction of Ag+ cations from 13 percent to 67 percent.The acid strength of the protons observed at 6.4 ppm is higher than that of the protons at 9.3 ppm.The catalytic activity of partially reduced Ag3PW12O40 for the isomerization of 3,3-dimethylbut-1-ene and hexane reversibly changes with hydrogen pressure.
Silica supported copper nanoparticles prepared via surface organometallic chemistry: active catalysts for the selective hydrogenation of 2,3-dimethylbutadiene
Boukebbous,Merle,Larabi,Garron,Darwich,Laifa,Szeto,De Mallmann,Taoufik
, p. 427 - 431 (2017)
2,3-Dimethylbutadiene can be highly selectively hydrogenated to 2,3-dimethyl-1-butene with a new catalyst based on silica supported copper nanoparticles (Cu-NPs) prepared via surface organometallic chemistry. Mesityl-copper was firmly grafted onto silica and the reduction of the resulting surface species under hydrogen at 350 °C led to well-dispersed Cu-NPs. Prior to catalytic tests, the final catalysts as well as the intermediates were characterised by DRIFT, SS NMR, EPR, TEM, XRD and elemental analyses.
Studies on Nickel-Containing Ziegler-Type Catalysts. IV. Dimerization of Propylene to 2,3-Dimethylbutenes. Part-II
Sato, Hiroshi,Tojima, Hideto
, p. 3079 - 3084 (1993)
A small amount of water was found to increase the activity of catalyst (A) for the selective dimerization of propylene to 2,3-dimethylbutenes (DMBS), Ni(naph)2/AlEt3/PR3/Diene/Chlorinated phenol, (A) where Ni(naph)2 denotes nickel naphthenate. The activity increased by about three to five times upon the addition of H2O in amounts of 0.2 to 0.8 mole per mole of AlEt3; the maximum activity was obtained at around 0.5 molar ratio of H2O to AlEt3. On the other hand, the reaction product between H2O and AlEt3 in a molar ratio of 0.5 was isolated and was identified to be μ-oxo-bis(diethylaluminum), the accelerating effect of which was also proved to be high. It is, therefore, concluded that the Lewis acidity of μ-oxo-bis(diethylaluminum) activates the Ni-H bond of the active species through coordination to the square-planar complex of nickel.
Synthesis and Molecular Structure of the Cyclic Hexamer of 2,3-Dimethylbutene Aluminium Monochloride
Dohmeier, Carsten,Mattes, Rainer,Schnoeckel, Hansgeorg
, p. 358 - 359 (1990)
The compound cyclo->6(μ-Cl)6Al6, (AlCl*DMB)6, prepared as a toluene solvate from a solution of AlCl and dimethylbutadiene in toluene, has been characterized crystallographically.
Studies on Nickel-Containing Ziegler-Type Catalysts. III. Dimerization of Propylene to 2,3-Dimethylbutenes. Part-I
Sato, Hiroshi,Noguchi, Takanobu,Yasui, Seimei
, p. 3069 - 3078 (1993)
A new selective catalyst was developed for the dimerization of propylene to 2,3-dimethylbutenes (DMBS). It comprises five components: nickel naphthenate (Ni(naph)2)/AlEt3/PR3/diene/chlorinated phenol. Among them, chlorinated phenol is an essential component for activating the catalyst. Both the dimerization of propylene and the isomerization of the produced 2,3-dimethyl-1-butene (DMB-1) to 2,3-dimethyl-2-butene (DMB-2) are accelerated in proportion to the content of the chlorinated phenol as well as to the number of chlorine atoms on the chlorinated phenol. These effects are attributed to the Lewis acidity of the reaction product between AlEt3 and the chlorinated phenol. Thus, either DMB-1 or DMB-2 can be produced selectively by controlling the composition of the catalyst. The content of DMBS mainly depends upon the phosphine ligand; this ligand effect is discussed in terms of the 31P NMR chemical shift. A high content of DMBS of up to 85percent in propylene dimers was attained when phosphines with chemical shifts between 0 and -30 ppm were used.
Reactions of Alkenes and the Equilibration of Hydrogen and Deuterium on Zirconia
Bird, Robert,Kemball, Charles,Leach, H. Frank
, p. 3069 - 3082 (1987)
The hydrogenation of various alkenes, the equilibration of H2/D2 and the isomerization of some C6-alkenes have been studied over a range of temperatures on zirconia catalysts.Products from the reaction of some of the alkenes with deuterium were examined by (2)D n.m.r. spectroscopy.The rate of hydrogenation varied only to a small extent with the nature of the alkene, apart from some steric hindrance with some of the C6-compounds, and the supply of hydrogen to the surface appeared to be rate-determining.Reactions of alkenes with deuterium below 400 K gave D2-alkanes.As the temperature was raised, exchange of alkene was observed to an increasing extent, and the location of the deuterium atoms in the products provided evidence of possible mechanisms.
