- A Drastic Effect of TEMPO in Zinc-Catalyzed Stannylation of Terminal Alkynes with Hydrostannanes via Dehydrogenation and Oxidative Dehydrogenation
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With a system consisting of a catalytic zinc Lewis acid, pyridine, and TEMPO in a nitrile medium, terminal alkynes coupled with HSnBu3, providing alkynylstannanes with structural diversity. The resulting alkynylstannane, without being isolated, could be directly used for Pd- and Cu-catalyzed transformations to deliver internal alkynes and more intricate tin-atom-containing molecules. Mechanistic studies indicated that TEMPOSnBu3 formed in situ from TEMPO and HSnBu3 works to stannylate the terminal alkyne in collaboration with the zinc catalyst, and that both of dehydrogenation and oxidative dehydrogenation processes are uniquely involved in a single reaction. (Figure presented.).
- Kai, Yuichi,Oku, Shinya,Sakurai, Kyoko,Tani, Tomohiro,Tsuchimoto, Teruhisa
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supporting information
(2019/08/21)
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- Fluoride ion mediated reactions of disubstituted acetylenes Me3SiCCMMe3 (M=C, Si, Ge, Sn) with terminal acetylenes
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The CsF-18-crown-6 mediated reactions of disubstituted acetylenes Me3SiCCMMe3 (M=C, Si, Ge, Sn) with phenylacetylene and 2-methyl-5-pyridylacetylene in benzene have been studied. The first step of the reaction is the deprotonation of
- Lukevics, Edmunds,Rubina, Kira,Abele, Edgars,Fleisher, Mendel,Arsenyan, Pavel,Grinberga, Solveiga,Popelis, Juris
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- Versatile routes to mono- and bis(alkynyl) manganese(II) and manganese (III) complexes via manganocenes
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With the manganocenes (RC5H4)2Mn (R = H, Me) as starting materials, paramagnetic d5 half-sandwich complexes (RC5H4)Mn(dmpe)(C≡CR′) (dmpe = 1,2-bis(dimethylphosphino)-ethane; R = Me, R′ = Ph, 1a; R = Me, R′ = SiMe3, 2a; R = H, R′ = Ph, 1b; R = H, R′ = SiMe3, 2b) have been prepared by the reaction with terminal or SnMe3-substituted acetylenes and dmpe. The derivatives 1a and 2a could be isolated, while 1b and 2b have been identified in mixtures with the bis(dmpe)bis(acetylide)manganese species 3 (R′ = Ph) and 4 (R′ = SiMe3). The latter compounds are obtained as the sole products, when the manganocenes are reacted with dmpe and the corresponding acetylenes in a 1:2:2 ratio. 1a and 2a can be reversibly oxidized to the corresponding cationic Mn(III) complexes [(MeC5H4)Mn(dmpe)-(C≡CR′)][BF4] (R′ = Ph, [1a]+; R′ = SiMe3, [2b]+). Compounds 1a and 2a act as scavengers of H? radicals in the 1:1:1 reaction mixtures or in the presence of n-Bu3SnH or (C5Me5)Mo-(CO)3H, forming the vinylidene species (MeC5H4)Mn(dmpe)(=C=C(H)R′) (R′ = Ph, 5; R′ = SiMe3, 6). In the absence of a special H? donor, 1a slowly dimerizes to give the binuclear complex 7. A similar process occurs with [1a]+ to form the bis(carbyne) complex 8. 8 can be reduced to 7 by a reaction with 2 equiv of (MeC5H4)2Co, and in turn 7 can be oxidized to 8 with 2 equiv of a ferrocenium salt. Equal amounts of 7 and 8 comproportionate to afford the mixed-valence complex [7]+. If applicable, the new compounds have been characterized by spectroscopic (NMR, EPR, near-IR) and electrochemical measurements, as well as X-ray diffraction studies (2a, 5, 7, and 8) and DFT calculations.
- Unseld, Dieter,Krivykh, Vassily V.,Heinze, Katja,Wild, Ferdinand,Artus, Georg,Schmalle, Helmut,Berke, Heinz
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p. 1525 - 1541
(2008/10/08)
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- Alkynyl-siibstituted tricarbonyl(cyclobutadlene)iron complexes: coupling of complexes sfannylalkynes
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The synthesis of mono-, di-, tri- and tetraalkynylated tricartaonyl(cyclobutadiene)iron complexes is accomplished by a repetitive metalation/iodination/coupling sequence. Application of this sequence leads to the synthesis of oligomeric cyclobutadiene complexes with various topologies, inter alia to the synthesis of a perethynylated aimer 24. Alternatively a one-step coupling procedure (Stille-Farina) has been used to synthesize tetraalkynylated tricarbonyl(cyclobutadiene)irons 26, VCH Verlagsgesellschaft mbH, : 1996.
- Bunz, Uwe H. F.,Jutta
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p. 785 - 797
(2007/10/03)
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- The Synthesis and Some Properties of the First Boron-Stabilized Alkenyl Carbanions
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Calculations indicate a high degree of stabilization of H2BC=CH2 and that it has an allene-type structure H2B=C=CH2.Routes to boron-stabilized alkenyl carbanions have been established for the first time, and alkylation and protonation studies are described.
- Pelter, Andrew,Smith, Keith,Parry, David E.,Jones, Kevin D.
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- Addition of stannyl phosphines to alkynes and allenes
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Diphenyl(trimethylstannyl)phosphine adds to alkynes (both terminal and nonterminal) and allenes under free radical conditions.The former reaction occurs regiospecifically with preferential formation of E-isomers, the latter regioselectively.Product identi
- Mitchell, Terence N.,Belt, Heinz-Joachim
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p. 167 - 176
(2007/10/02)
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- A 15N NMR Study of Some Trimethylstannylhydrazines
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The trimethylstannylhydrazines (Me3Sn)2N-NMe2 (1), Me3Sn(Me)N-N(Me)SnMe3 (2), (Me3Sn)2N-N(Me)SnMe3 (3), and (Me3Sn)2N-N(Ph)SnMe3 (4) have been studied by 15N NMR at natural abundance.A correlation between δ15N of hydrazines and δ15N of corresponding amines (replacement of one N-atom by the CH-unit) is proposed in order to estimate δ15N values and to support the non-trivial assignment of 15N resonances of hydrazines.Geminal coupling constants 2J(119SnN15N) have been observed for the first time.Their relative magnitude is related to the probability of the N-Sn bond being in cis-position with respect to the orientation of the lone electron pair at the 15N nucleus in the 119Sn-N-15N fragment.Treatment of 4 with phenylacetylene causes non-selective cleavage of the Sn-N bonds, leading to the trimethylstannylhydrazines 5 and 6 which have been characterized by 119Sn and 15N NMR spectroscopy in solution. - keywords: Trimethylstannylhydrazines, Conformation, 119Sn NMR Spectra, 15N NMR Spectra, 119Sn-15N Coupling Constants
- Wrackmeyer, Bernd,Gasparis-Ebeling, Theo,Noeth, Heinrich
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p. 653 - 658
(2007/10/02)
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- FLUXIONALITY OF M2C2 TETRAHEDRAL CLUSTERS CONTAINING CYCLOPENTADIENYLDICARBONYLMETAL VERTICES: UNEXPECTEDLY DIFFERENT BEHAVIOUR OF MOLYBDENUM AND TUNGSTEN
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The syntheses of a series of molecules 2(RCCR'), where Cp' = C5Me5, C5H4Me; M = Mo, W; R = Ph, R' = H, Et, CO2Me, SnMe3 are described.The molybdenum complexes possess a semi-bridged carbonyl thus rendering the molecules chiral; their 13C NMR spectra show four carbonyl resonances and two cyclopentadienyl environments.The barrier to racemisation depends on the bulk of the substituents on the ring.In contrast, the NMR spectra of the tungsten analogues show only single carbonyl and cyclopentadienyl environments even at -90 deg C and 9.4 T.
- Bougeard, Peter,Peng, Shane,Mlekuz, Michael,McGlinchey, Michael J.
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p. 383 - 392
(2007/10/02)
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- REACTIONS OF DIPHOSPHINEPLATINUM(II) OXALATE COMPLEXES WITH PHENYLACETYLENE. FORMATION OF PHENYLALKYNYLPLATINUM COMPLEXES
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reacts thermally with PhCCH to produce CPh)2(dppe)>, which has been prepared by alternative routes.Similar treatment of initially produces CPh)2(dpmm)>, which rearranges to give cis,cis-CPh)4(μ-dppm)2>.Reaction of with PhCCH/KOH/18-crown-6, or with (PhCC)SnMe3, gives CPh)2(dpmm)>, which may be converted to the cis,cis-dimer by addition of oxalic acid.Ultraviolet irradiation or refluxing with a trace amount of dppm converts CPh)2(dppm)> to trans,trans-CPh)4(μ-dppm)2>, but the cis,cis-dimer is stable under these conditions. (L = PPh3, PEt3) complexes also react thermally with PhCCH to yield CPh)2L2> species.
- Anderson, Gordon K.,Lumetta, Gregg J.
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p. 257 - 264
(2007/10/02)
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