604-88-6Relevant academic research and scientific papers
Aktivierung von Kohlendioxid an Uebergangsmetallzentren: Selektive Cooligomerisation mit Hexin(-3) durch das Katalysatorsystem Acetonitril/Trialkylphosphan/Nickel(0) und Struktur eines Nickel(0)-Komplexes mit side-on gebundenem Acetonitril
Walther, Dirk,Schoenberg, Hartmut,Dinjus, Eckard,Sieler, Joachim
, p. 377 - 388 (1987)
CO2 reacts with hexyne(-3) in a catalytic reaction under formation of tetraethyl-2-pyrone, when the catalytic system alkyl3P/acetonitrile/nickel(0) is used.The selectivity of this homogeneous-catalytic reaction can be increased to values of 96percent when phosphanes of high basicity and small cone angle are used.The investigation of the system Ni(COD)2/tricyclohexylphosphane/acetonitrile shows that acetonitrile can act as ligand in complexes of nickel(0).A yellow-brown tetranuclear complex was isolated, the structure of which was determined by X-ray diffraction studies.Acetonitrile acts as bridging ligand and is coordinated alkyne-analogously to one nickel center with its triple bond.The free electron pair of the nitrogen atom is bonded to a second nickel atom.Some reaction steps of this selective catalytic reaction are discussed.This reaction represents the first example of a selective homogeneous-catalytic co-oligomerization between CO2 and an unsaturated substrate which takes place under C-C linkage with a 3d-transition metal.
Elementary steps of iron catalysis: Exploring the links between iron alkyl and iron olefin complexes for their relevance in C-H activation and C-C bond formation
Casitas, Alicia,Krause, Helga,Goddard, Richard,Fürstner, Alois
, p. 1521 - 1526 (2015)
The alkylation of complexes 2 and 7 with Grignard reagents containing β-hydrogen atoms is a process of considerable relevance for the understanding of C-H activation as well as C-C bond formation mediated by low-valent iron species. Specifically, reaction of 2 with EtMgBr under an ethylene atmosphere affords the bis-ethylene complex 1 which is an active precatalyst for prototype [2+2+2] cycloaddition reactions and a valuable probe for mechanistic studies. This aspect is illustrated by its conversion into the bis-alkyne complex 6 as an unprecedented representation of a cyclo-addition catalyst loaded with two substrates molecules. On the other hand, alkylation of 2 with 1 equivalent of cyclohexylmagnesium bromide furnished the unique iron alkyl species 11 with a 14-electron count, which has no less than four β-H atoms but is nevertheless stable at low temperature against β-hydride elimination. In contrast, the exhaustive alkylation of 1 with cyclohexylmagnesium bromide triggers two consecutive C-H activation reactions mediated by a single iron center. The resulting complex has a diene dihydride character in solution (15), whereas its structure in the solid state is more consistent with an η3-allyl iron hydride rendition featuring an additional agostic interaction (14). Finally, the preparation of the cyclopentadienyl iron complex 25 illustrates how an iron-mediated C-H activation cascade can be coaxed to induce a stereoselective C-C bond formation. The structures of all relevant new iron complexes in the solid state are presented.
Bimetallic Mechanism for Alkyne Cyclotrimerization with a Two-Coordinate Fe Precatalyst
Chakarawet, Khetpakorn,Hait, Diptarka,Head-Gordon, Martin,Tilley, T. Don,Witzke, Ryan J.
, p. 7800 - 7807 (2020)
The two-coordinate compound (IPr)Fe[N(SiMe3)DIPP] (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene; DIPP = 2,6-diisopropylphenyl) catalyzes the cyclotrimerization of alkynes to arenes. Treatment of the Fe complex with 1 equiv of diphenylacetylene results in the formation of a bimetallic bridging alkyne complex, along with dissociation of IPr from Fe. At elevated temperatures, the bridging alkyne complex undergoes oxidative coupling to form a dimetallacyclopentadiene complex, formally by a one-electron oxidation at each metal center. Each complex catalyzes the cyclotrimerization of diphenylacetylene. Kinetic studies exhibit first-order dependence on the bimetallic complexes, providing further support for the presence of these species in the catalytic cycle. DFT calculations support the experimental mechanistic data and suggest that the catalytic cycle is completed by binding of an alkyne to the diene complex, followed by insertion to form a hexatriene species that then undergoes ring closure to form an inverse sandwich complex, [DIPP(Me3Si)N]Fe(η6-arene)Fe[N(SiMe3)DIPP]. The arene product is then displaced by alkyne to close the catalytic cycle.
Ring Expansion to 1-Bromo-1-alumacyclonona-2,4,6,8-tetraene by Insertion of Two Alkyne Molecules into the AlC Bonds
Agou, Tomohiro,Wasano, Tatsuya,Sasamori, Takahiro,Guo, Jing-Dong,Nagase, Shigeru,Tokitoh, Norihiro
, p. 9568 - 9571 (2015)
Treatment of 1-bromo-2,3,4,5-tetraethylalumole (1) with 3-hexyne afforded the corresponding product 1-bromo-1-alumacyclonona-2,4,6,8-tetraene (2), accompanied by the formation of hexaethylbenzene. In the crystalline state, 2 forms a Br-bridged dimer with a pseudo C2-symmetric and twisted AlC8 nine-membered ring. Deuterium-labeling experiments and DFT calculations on the reaction of 1 with 3-hexyne suggested that 1-bromo-1-alumacyclohepta-2,4,6-triene, which is formed by the insertion of one molecule of 1-hexyne into the AlC bond of alumole 1, is the key intermediate for the generation of 2 as well as hexaethylbenzene. Expanding Al's horizons: A stable alumacyclononatetraene 1 was obtained by the reaction of the corresponding alumole with 3-hexyne accompanied by the formation of hexaethylbenzene. Deuterium-labeling experiments and DFT calculations suggested that an alumacycloheptatriene is the key intermediate (see picture).
Alkyne-Induced Facile C-C Bond Formation of Two I2-Alkynes on Dinuclear Tantalum Bis(alkyne) Complexes to Give Dinuclear Tantalacyclopentadienes
Yamamoto, Keishi,Tsurugi, Hayato,Mashima, Kazushi
, p. 1573 - 1581 (2016)
The dinuclear tantalum-alkyne complexes [(2-RCi -CR)TaCl2]2(I-OMe)2(-thf) (2a, R = Et; 2b, R = nPr) were synthesized by treating the mononuclear tantalum-alkyne complexes (I2-RCI- CR)TaCl3(dme) (1a, R = Et; 1b, R = nPr) with 1 equiv of NaOMe in THF. We found that adding a catalytic amount (20 mol %) of 3-hexyne to 2a induced the spontaneous formation of Ta2Cl4(OMe)2(-C4Et4)(thf) (4a). Similarly, Ta2Cl4(OMe)2(-C4nPr4)(thf) (4b) was obtained by treatment of 2b with a catalytic amount (20 mol %) of 4-octyne. Reaction of 4a,b with 4-dimethylaminopyridine gave 4-dimethylaminopyridine-coordinated complexes 6a,b, whose structures were elucidated by the X-ray structure of 6a. We conducted a control experiment in which 10 equiv of 4-octyne was added to 2a to give Ta2Cl4(OMe)2(-C4-2,3-nPr2-4,5-Et2)(thf) (7) in 90% yield, indicating that free 4-octyne reacted with the tantalacyclopropene moiety of 2a to form a dissymmetric tantalacyclopentadiene, followed by the release of 3-hexyne. The catalytic activity of 4a-6a for [2 + 2 + 2] cyclotrimerization of 3-hexyne was examined, and we found that their activities were in the order 5a > 4a 6a.
Graphdiyne:Structure of Fluorescent Quantum Dots
Chen, Chunying,Guo, Jie,Guo, Mengyu,Jin, Weiyue,Li, Yuliang,Liu, Huibiao,Wang, Fuhui
, p. 16712 - 16716 (2020)
Graphdiyne (GDY) as an emerging two-dimensional carbon allotrope exhibits excellent performance in energy chemistry, catalytic chemistry, optoelectronics, electronics, etc. because of the unique structure combining an sp- and sp2-hybrid carbon network. However, the poor solubility of pristine GDY is a major obstacle to its applications in many fields. Proposed here is a facile strategy to control the preparation of GDY quantum dots (GDY-Py QDs), in which pyrene groups are covalently linked to GDY by using a Sonogashira cross-coupling reaction. The as-prepared GDY-Py QDs, with an average diameter of about 3±0.1 nm, show superior dispersibility in many organic solvents and water. The GDY-Py QDs display not only bright fluorescent with a high relative quantum yield (QY) of 42.82 %, but they are also well-behaved as contrast agents in cell imaging. The GDY-Py QDs are bestowed with high stability and non-cytotoxicity, and exhibit long fluorescent times, and have potential for optical imaging and biomedical applications.
Three-coordinate Bis(N-heterocyclic carbene)iron(0) complexes with alkene and alkyne ligation: Synthesis and characterization
Wang, Lijun,Cheng, Jun,Ma, Yingjie,Chen, Qi,Leng, Xuebing,Deng, Liang
, (2021)
The synthesis and characterization of the three-coordinate iron(0) complex [(IMesMe)2Fe(η2-CH2CHSiMe3)] (1, IMesMe = 1-(2′4′6′-trimethylphenyl)-3-methyl-2-ylidene) as well as its reactions with alkynes have been investigated. Complex 1 was prepared in 76% yield from the reaction of FeCl2 with two equiv. of IMesMe, one equiv. of CH2[dbnd]CHSiMe3, and two equiv. of KC8. The characterization data obtained from solution magnetic susceptibility measurement, single-crystal X-ray diffraction study, and 57Fe M?ssbauer spectroscopy, in combination with theoretical calculations suggest an S = 1 ground spin-state for 1 that has enhanced iron-to-alkene π-backdonation as compared to that in the bis(alkene) complex [(IPr)Fe(η2-CH2CHSiMe3)2] (IPr = 1,3-di-(2′6′-diisopropylphenyl)-2-ylidene). The equimolar reactions of 1 with the internal alkynes PhC[tbnd]CPh, EtC[tbnd]CEt, and PhC[tbnd]CMe yield the iron(0) alkyne complexes [(IMesMe)2Fe(η2-RCCR′)] (R = R′ = Ph, 2; R = R′ = Et, 3; R = Ph, R′ = Me, 4). In addition, the reaction of 1 with five equiv. of PhC[tbnd]CMe is found to give a paramagnetic cyclobutadiene iron complex [(IMesMe)2Fe(η4-C(Ph)C(CH3)C(Ph)C(CH3))] (5). The molecular structure and 57Fe M?ssbauer spectroscopy data indicate an S = 1 ground spin-state for 2–5. Complex 1 is an effective catalyst for cyclotrimerization reactions of internal alkynes R1C[tbnd]CR2 (R1 = R2 = Ph; R1 = R2 = Et; R1 = Me, R2 = Ph).
Straightforward Access to Stable, 16-Valence-Electron Phosphine-Stabilized Fe0 Olefin Complexes and Their Reactivity
Burcher, Benjamin,Sanders, Kevin J.,Benda, Ladislav,Pintacuda, Guido,Jeanneau, Erwann,Danopoulos, Andreas A.,Braunstein, Pierre,Olivier-Bourbigou, Hélène,Breuil, Pierre-Alain R.
, p. 605 - 613 (2017)
The use of the dialkene divinyltetramethyldisiloxane (dvtms) allows easy access to the reactive 16-valence-electron complexes [Fe0(L-L)(dvtms)] (L-L = dppe (1,2-bis(diphenylphosphino)ethane; 1), dppp (1,2-bis(diphenylphosphino)propane; 2), pyNMeP(iPr)2 (N-(diisopropylphosphino)-N-methylpyridin-2-amine; 4), dipe (1,2-bis(diisopropylphosphino)ethane; 5)) and [Fe0(L)2(dvtms)] (L = PMe3; 3) by a mild reductive route using AlEt2(OEt) as reducing agent. In contrast, by the same methodology, the 18-valence-electron complexes [Fe0(L-L)2(ethylene)] (L-L = dppm (1,2-bis(diphenylphosphino)methane; 6), dppa (1,2-bis(diphenylphosphino)amine; 7), dppe (8)) were obtained, which do not contain dvtms. In addition, a combined DFT and solid-state paramagnetic NMR methodology is introduced for the structure determination of 5. A comparative study of the reactivity of 1, 2, 4-6, and 8 with 3-hexyne highlights emerging mechanistic implications for C-C coupling reactions using these complexes as catalysts.
Synthesis and Structures of Bis(indolyl)-Coordinated Titanium Dichlorido Complexes and Their Catalytic Application in the Cyclotrimerization of Alkynes
Itoh, Keigo,Miura, Narumi,Miyamoto, Ryo,Ohta, Shun,Okazaki, Masaaki,Saitoh, Keiichiro,Satoh, Sora
, p. 2826 - 2835 (2021/09/02)
The impact of the terminal ligands on the titanium center on the coordination features of deprotonated 2,2′-bis(indolyl)methanes (henceforth: bis(indolyl)s) was studied via a structural comparison between {bis(indolyl)}Ti(NEt2)2 complexes and the corresponding dichlorido complexes. As a result, several flexible aspects of bis(indolyl) coordination were found. For example, it was revealed that an η1-coordinated indolyl moiety can change its coordination mode to coordination via the five-membered ring of indolyl when the terminal diethylamido ligands are replaced by chlorido ligands. Moreover, we found that the methoxy group in the central aromatic ring of the bis(indolyl) ligand can coordinate to the titanium center. The synthesized dichlorido complexes were applied for catalytic alkyne cyclotrimerization reactions, as Ti-based catalyst systems are less developed than Co-, Ni-, Ru-, Rh-, and Ir-based systems. During this study, the cyclotrimerization of HCCSiMe3 was found to preferentially produce the 1,3,5-form (1,3,5-form:1,2,4-form = 79:21), contrary to the typical trend of transition-metal-mediated alkyne cyclotrimerization, and the isolated yield (72%) is the highest among the known 1,3,5-favoring reactions using Ti-based catalyst systems. Furthermore, the reaction mechanism was experimentally verified to proceed through a typical stepwise mechanism involving monomeric species.
Generation of Masked TiIIIntermediates from TiIVAmides via β-H Abstraction or Alkyne Deprotonation: An Example of Ti-Catalyzed Nitrene-Coupled Transfer Hydrogenation
Pearce, Adam J.,Cheng, Yukun,Dunscomb, Rachel J.,Tonks, Ian A.
supporting information, p. 3771 - 3774 (2020/11/13)
Simple Ti amide complexes are shown to act as sources for masked TiII intermediates via several pathways, as demonstrated through the investigation of a unique Ti-catalyzed nitrene-coupled transfer hydrogenation of 3-hexyne. This reaction proceeds through reduction of azobenzene by a masked TiII catalyst, wherein both amines and 3-hexyne can serve as the hydrogen source/reductant for Ti by forming putative titanaziridines via β-H abstraction or putative titanacyclopentynes via protonolysis, respectively.
