1552-12-1Relevant articles and documents
Inverse Isotope Effects in Single-Crystal to Single-Crystal Reactivity and the Isolation of a Rhodium Cyclooctane σ-Alkane Complex
Doyle, Laurence R.,Furfari, Samantha K.,Galpin, Martin R.,Hicks, Scott A.,Lloyd-Jones, Guy C.,MacGregor, Stuart A.,Martínez-Martínez, Antonio J.,Tegner, Bengt E.,Weller, Andrew S.,Whitwood, Adrian C.
supporting information, p. 284 - 292 (2022/02/10)
The sequential solid/gas single-crystal to single-crystal reaction of [Rh(Cy2P(CH2)3PCy2)(COD)][BArF4] (COD = cyclooctadiene) with H2 or D2 was followed in situ by solid-state 31P{1H} NMR spectroscopy (SSNMR) and ex situ by solution quenching and GC-MS. This was quantified using a two-step Johnson-Mehl-Avrami-Kologoromov (JMAK) model that revealed an inverse isotope effect for the second addition of H2, that forms a σ-alkane complex [Rh(Cy2P(CH2)3PCy2)(COA)][BArF4]. Using D2, a temporal window is determined in which a structural solution for this σ-alkane complex is possible, which reveals an η2,η2-binding mode to the Rh(I) center, as supported by periodic density functional theory (DFT) calculations. Extensive H/D exchange occurs during the addition of D2, as promoted by the solid-state microenvironment.
Mechanistic Insight into High-Spin Iron(I)-Catalyzed Butadiene Dimerization
Lee, Heejun,Campbell, Michael G.,Hernández Sánchez, Raúl,B?rgel, Jonas,Raynaud, Jean,Parker, Sarah E.,Ritter, Tobias
supporting information, p. 2923 - 2929 (2016/11/06)
Iron complexes are commonly used in catalysis, but the identity of the active catalyst is often unknown, which prevents a detailed understanding of structure-reactivity relationships for catalyst design. Here we report the isolation and electronic structure determination of a well-defined, low-valent iron complex that is an active catalyst in the synthesis of cis,cis-1,5-cyclooctadiene (COD) from 1,3-butadiene. Spectroscopic and magnetic characterization establishes a high-spin Fe(I) center, which is supported by DFT studies, where partial metal-ligand antibonding orbital population is proposed to allow for facile ligand exchange during catalysis.
Guanidinato complexes of iridium: Ligand-donor strength, O2 reactivity, and (alkene)peroxoiridium(III) intermediates
Kelley, Matthew R.,Rohde, Jan-Uwe
, p. 2564 - 2580 (2013/04/10)
A series of seven [Ir{ArNC(NR2)NAr}(cod)] complexes (1a-1g; where R = Me or Et; Ar = Ph, 4-MeC6H4, 4-MeOC 6H4, 2,6-Me2C6H3, or 2,6-iPr2C6H3; and cod = 1,5-cyclooctadiene) were synthesized by two different methods from the neutral guanidines, ArN-C(NR2)NHAr, using either MeLi and [{Ir(cod)} 2(μ-Cl)2] or [{Ir(cod)}2(μ-OMe) 2]. Reaction of 1a-1g with CO produced the corresponding [Ir{ArNC(NR2)NAr}(CO)2] complexes (2a-2g), which were characterized by NMR and solution- and solid-state IR spectroscopy. Complexes 1b (R = Et, Ar = Ph), 1d (R = Et, Ar = 4-MeC6H4), 1f (R = Me, Ar = 2,6-Me2C6H3), and 2b (R = Et, Ar = Ph) were characterized by X-ray crystallography as mononuclear complexes with a guanidinato-κ2N,N′ ligand and a cod or two CO ligands coordinated to the Ir center in a distorted square-planar environment. On the basis of the CO stretching frequencies of 2a-2g [avg. νCO (n-pentane) = 2016-2019 cm-1] and the alkene 13C chemical shifts of 1a-1g [δ(13CC-C) = 58.7-61.0 ppm], the donor strength of the guanidinato ligands was evaluated and compared to that of related monoanionic ligands. Reaction of 1a-1g in solution with O2 at 20 C afforded (alkene)peroxoiridium(III) intermediates, [Ir{ArNC(NR 2)NAr}(cod)(O2)] (3). The steric properties of the supporting ligand play a decisive role in O2 binding in that complexes without ortho substituents react largely irreversibly with O 2 (1a-1e; where Ar = Ph, 4-MeC6H4 or 4-MeOC6H4), whereas complexes with ortho substituents exhibit fully reversible O2 binding (1f and 1g; where Ar = 2,6-Me2C6H3 or 2,6-iPr 2C6H3). Complexes 3a-3f were characterized by 1H NMR and IR spectroscopy (νOO = 857-872 cm -1). Decay of the new intermediates and subsequent reaction with cod produced 4-cycloocten-1-one and the respective IrI precursor.
ANTIOXIDANTS IN FISH OIL POWDER AND TABLETS
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, (2012/06/30)
This invention relates to antioxidants and combinations of antioxidants used to prevent oxidation of pharmaceutical and nutraceutical products in the form of powders, granulates, tablets, emulsions, gels and the like comprising one or more fatty acids and/or fatty acid derivatives and, optionally, at least one carbohydrate carrier alone or together with vitamins, minerals and/or pharmaceuticals. In particular, the invention concerns the use of antioxidants to reduce oxidation of powders, tablets, gels and emulsions comprising high concentrations and high doses of omega-3 fatty acids or derivatives thereof.
PROCESS FOR PRODUCING HIGH PURITY EXO-ALKENYLNORBORNENE
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Page/Page column 12, (2009/07/02)
Embodiments of the present invention are directed generally to methods for producing high purity exo-alkenylnorbornenes from a mixture of conformational isomers thereof.
Estimating the limiting reducing power of SmI2/H 2O/amine and YbI2/H2O/amine by efficient reduction of unsaturated hydrocarbons
Dahlen, Anders,Nilsson, Ake,Hilmersson, Goeran
, p. 1576 - 1580 (2007/10/03)
The mixture of samarium diiodide, amine, and water (SmI2/H 2O/Et3N) is known to be a particularly powerful reductant, but until now the limiting reducing power has not been determined. A series of unsaturated hydrocarbons with varying half-wave reduction potentials (E 1/2 = -1.6 to -3.4 V, vs SCE) have been treated with SmI 2/H2O/Et3N and YbI2/H 2O/Et3N, respectively. All hydrocarbons with potentials of -2.8 V or more positive were readily reduced with SmI2/H 2O/Et3N, whereas all hydrocarbons with potentials of -2.3 V or more positive were readily reduced using YbI2/H 2O/Et3N. This defines limiting values of the chemical reducing power of SmI2/H2O/Et3N to -2.8 V and of YbI2/H2O/Et3N to -2.3 V vs SCE.
Chiral monophosphites as ligands for assymetrical synthesis
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, (2008/06/13)
Certain chiral monophosphites and their monothio derivatives are suitable as ligands in the asymmetrical transition-metal-catalyzed hydrogenation, hydroborination and hydrocyanation of prochiral olefins, ketones and imines.
Process for preparing cyclododecatrienes with recycling of the catalyst
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Page column 5, (2008/06/13)
Cyclododecatrienes may be prepared in a continuous process by reacting 1,3-butadiene in the presence of a catalyst system and cyclooctadiene and/or cyclododecatriene. The resulting crude cyclododecatriene product may be separated from this mixture by distillation, and 50 to 100% of the catalyst system may be recycled back into the process.
Discontinuous pressure effect upon enantiodifferentiating photosensitized isomerization of cyclooctene
Kaneda, Masayuki,Asaoka, Sadayuki,Ikeda, Haruhiko,Mori, Tadashi,Wada, Takehiko,Inoue, Yoshihisa
, p. 1272 - 1273 (2007/10/03)
A hydrostatic pressure of up to 750 MPa induced discontinuous changes in the enantiomeric excess of the (E)-isomer obtained in the enantiodifferentiating photoisomerization of (Z)-cyclooctene and (Z,Z)-cycloocta-1,5-diene, sensitized by chiral benzene-1,2,4,5-tetracarboxylates; indicating a switching of the enantiodifferentiation mechanism, which is attributable to dramatic conformational changes of chiral alkoxycarbonyl auxiliaries at a specific pressure.
Mono- and bisadducts from the addition of thianthrene cation radical salts to cycloalkenes and alkenes
Qian, Ding-Quan,Shine, Henry J.,Guzman-Jimenez, Ilse Y.,Thurston, John H.,Whitmire, Kenton H.
, p. 4030 - 4039 (2007/10/03)
Thianthrene cation radical salts, Th.+ X-(X- = a, ClO4-; b, PF6-; c, SbF6-), add to cycloalkenes (C5-C8) in acetonitrile (MeCN) to form 1,2-bis(5-thianthreniumyl)cycloalkane salts and 1,2-(5,10-thianthreniumdiyl)cycloalkane salts, most of which have now been isolated and characterized. These are called bis- (3, 6, 9, 12) and monoadducts (4, 7, 10, 13). The proportional amount of the monoadduct obtained in the initial stage of the reaction varied with the cycloalkene in the order C6 ? C5 7 ? C8. Thus, the ratio bis:mono for C5 and C7 was, respectively, about 80/20 and 50/50. In contrast, only about 5% of the C6 monoadduct (7a) and none of 7b, c was obtained, while for C8 none of the bisadducts 12a-c was found. Bisadducts 3 and 9 lost thianthrene (Th) slowly in MeCN solution and changed into monoadducts 4 and 10. A comparable change from 6a into 7a was not observed. The monoadducts, themselves, lost a proton slowly in dry MeCN and opened into 1-(5-thianthreniumyl)cycloalkenes (5, 8, 11, 14). With 3 and 9, particularly, it was possible to follow with NMR spectroscopy the succession of changes, for example, 3 to 4 to 5. The opening of a monoadduct was made faster by adding a small amount of water to the solution. The bisadducts of 4-methylcyclohexene (15a) and 1,5- cyclooctadiene (17a) were isolated and characterized. Although a small amount of monodduct (16a) of 4-methylcyclohexene was found with NMR spectroscopy, it could not be isolated. Bis- and monoadducts were obtained also in additions of Th.+ ClO4- to acyclic alkenes, in relative amounts that, again, varied with the alkene. From cis-2-butene the dominant product was the bisadduct (18), while the monoaduct (19) was characterized with NMR spectroscopy but could not be isolated. In contrast, trans-3-hexene gave mainly the monoadduct (21), while the bis adduct (20) could not be isolated. With 4-methyl-cis-2-pentene, both bis- (22) and monoadduct (23) were isolated, the former being dominant. The conversion of 18 into 19 was characterized with NMR spectroscopy. In all cycloalkene bisadducts, the configurational relationship of the two thianthrenium groups was trans, while in the monoadducts, the bonds to the single thianthrene dication were (necessarily) cis. In both bis- and monoadducts of acyclic alkenes, the configuration of the alkene was retained. The mechanisms of addition with retention of configuration, of conversion of a bis- into a monoadduct, and of opening of a monoadduct are discussed. Products were identified with a combination of NMR spectroscopy, X-ray crystallography, elemental analysis, and (for cycloalkene adducts) reaction with thiophenoxide ion.
