- Design, Isolation, and Spectroscopic Analysis of a Tetravalent Terbium Complex
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Synthetic strategies to yield molecular complexes of high-valent lanthanides, other than the ubiquitous Ce4+ ion, are exceptionally rare, and thorough, detailed characterization in these systems is limited by complex lifetime and reaction and isolation conditions. The synthesis of high-symmetry complexes in high purity with significant lifetimes in solution and the solid state is essential for determining the role of ligand-field splitting, multiconfigurational behavior, and covalency in governing the reactivity and physical properties of these potentially technologically transformative tetravalent ions. We report the synthesis and physical characterization of an S4 symmetric, four-coordinate tetravalent terbium complex, [Tb(NP(1,2-bis-tBu-diamidoethane)(NEt2))4] (where Et is ethyl and tBu is tert-butyl). The ligand field in this complex is weak and the metal-ligand bonds sufficiently covalent so that the tetravalent terbium ion is stable and accessible via a mild oxidant from the anionic, trivalent, terbium precursor, [(Et2O)K][Tb(NP(1,2-bis-tBu-diamidoethane)(NEt2))4]. The significant stability of the tetravalent complex enables its thorough characterization. The stepwise development of the supporting ligand points to key ligand control elements for further extending the known tetravalent lanthanide ions in molecular complexes. Magnetic susceptibility, electron paramagnetic resonance (EPR) spectroscopy, X-ray absorption near-edge spectroscopy (XANES), and density functional theory studies indicate a 4f7 ground state for [Tb(NP(1,2-bis-tBu-diamidoethane)(NEt2))4] with considerable zero-field splitting, demonstrating that magnetic, tetravalent lanthanide ions engage in covalent metal-ligand bonds. This result has significant implications for the use of tetravalent lanthanide ions in magnetic applications since the observed zero-field splitting is intermediate between that observed for the trivalent lanthanides and for the transition metals. The similarity of the multiconfigurational behavior in the ground state of [Tb(NP(1,2-bis-tBu-diamidoethane)(NEt2))4] (measured by Tb L3-edge XAS) to that observed in TbO2 implicates ligand control of multiconfigurational behavior as a key component of the stability of the complex.
- Rice, Natalie T.,Popov, Ivan A.,Russo, Dominic R.,Bacsa, John,Batista, Enrique R.,Yang, Ping,Telser, Joshua,La Pierre, Henry S.
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- Synthesis and reactivity of the stable silylene N,N′-di-tert-butyl-1,3-diaza-2-sila-2-ylidene
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The synthesis and several reactions of the stable silylene 1 (N,N′-di-tert-butyl-1,3-diaza-2-sila-2-ylidene) are reported. Overreduction of 1 with alkali metals results in the formation of a dimeric dianion, which can be trapped with a proton source to give the dihydride derivative 9. In the solid state or in concentrated solutions, 1 undergoes a reversible conversion into the novel tetrameric disilene, 10. 1 reacts with ethanol, phenol, and water via insertion into the O - H bond, and with iodomethane by insertion into the C - I bond. A reaction of 1 with the diene 2,3-dimethyl-1,3-butadiene affords the silacyclopentene, 15. This reaction is markedly different from the one found for the unsaturated analog of the silylene, 2, which catalyzes the conversion of this diene into a highly cross-linked polymer.
- Haaf,Schmedake,Paradise,West
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- Near quantitative synthesis of urea macrocycles enabled by bulky N-substituent
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Macrocycles are unique molecular structures extensively used in the design of catalysts, therapeutics and supramolecular assemblies. Among all reactions reported to date, systems that can produce macrocycles in high yield under high reaction concentration
- Yang, Yingfeng,Ying, Hanze,Li, Zhixia,Wang, Jiang,Chen, Yingying,Luo, Binbin,Gray, Danielle L.,Ferguson, Andrew,Chen, Qian,Z, Y.,Cheng, Jianjun
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- Method for synthesizing N, N-di-di-tert-butyl ethylenediamine
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The invention belongs to medicine. The invention relates to the field of organic synthesis, such as biological reagents. The invention specifically relates to a synthetic method N of N-di-tert-butyl ethylenediamine. The existing synthesis method has the advantages of tedious treatment steps, poor reaction selectivity, multiple by-products, difficult separation and low yield, and simultaneously adopts an expensive Pd / C catalyst, so that the reaction pressure is high, and the cost is high. The synthesis method is characterized in that the tert-butylamine and 40% glyoxal are condensed in toluene to form an imine, and a part of tert-butylamine is added into the organic phase after layered dehydration. N-di-tert-butyl ethylenediamine is obtained by catalytic hydrogenation of Raney nickel; 2:1 - 5.1. The reaction selectivity is better. The yield is high, and the cheap Raney nickel is adopted as a hydrogenation catalyst, so that the production cost is effectively reduced, the reaction is simple, and the operation is convenient.
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Paragraph 0016-0023
(2021/10/11)
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- Effect of ligand substituents in olefin polymerisation by half-sandwich titanium complexes containing monoanionic iminoimidazolidide ligands-MAO catalyst systems
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Various half-sandwich titanium complexes containing iminoimidazolidide ligands, CpTiCl2[1,3-R2(CH2N)2CN] (1a-d) [R = Ph (a), 2,6-Me2C6H3 (b), cyclohexyl (c), tBu (d)], have been employed as the catalyst precursors for ethylene polymerisation, syndiospecific styrene polymerisation, and copolymerisation of ethylene with 1-hexene in the presence of MAO cocatalyst; 1d showed the highest catalytic activity for ethylene polymerisation whereas 1b showed the highest activity for syndiospecific styrene polymerisation.
- Nomura, Kotohiro,Fukuda, Hiroya,Katao, Shohei,Fujiki, Michiya,Kim, Hyun Joon,Kim, Dong-Hyun,Zhang, Shu
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scheme or table
p. 7842 - 7849
(2011/09/20)
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- N,N′-dialkyl- and N-aIkyl-N-mesityl-substituted N-heterocyclic carbenes as ligands in Grubbs catalysts
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Various symmetrically and asymmetrically substituted N-heterocyclic carbene (NHC) ligands bearing aliphatic nitrogen-containing side groups have been synthesised. In our attempts to isolate the corresponding second-generation Grubbs catalysts, we were unsuccessful when using the symmetrical aliphatic NHC ligands. For the asymmetrical ligands bearing an aliphatic moiety on one side and an aromatic mesityl group on the other side, substitution of a phosphine ligand was achieved. The performance of a soformed series of Ru-based metathesis initiators has been evaluated for the ring-opening metathesis polymerisation (ROMP) of cycloocta-1,5-diene and the ring-dosing metathesis (RCM) of diethyl diallylmalonate.
- Ledoux, Nele,Allaert, Bart,Pattyn, Siegfried,Mierde, Hans Vander,Vercaemst, Carl,Verpoort, Francis
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p. 4654 - 4661
(2008/02/08)
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- Reaction of 1,2-dibromoethane with primary amines: Formation of N,N′-disubstituted ethylenediamines RNH-CH2CH2-NHR and homologous polyamines RNH-[CH2CH2NR]n-H
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The reaction of primary amines RNH2 (R: Me, Et, iPr, tBu and Ph) with 1,2-dibromoethane gave N,N′-disubstituted ethylenediamines R-NH-CH2CH2-NH-R (1) in yields ranging from 10% (1a; R=Me) to 70% (1d, R=tBu; 1e, R=Ph). Pipe
- Denk, Michael K.,Krause, Mike J.,Niyogi, Debyani F.,Gill, Nachhattarpal K.
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p. 7565 - 7570
(2007/10/03)
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- Carbanion-Accelerated Claisen Rearrangements. 8. Phosphonamide Anion-Stabilizing Groups
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The utility of various phosphonamide groups has been examined in the context of the carbanion-accelerated Claisen rearrangement (CACR).An extensive survey has identified the N,N'-dibenzyl-1,3,2-diazaphospholidine group 11 to be optimal in the ease of construction of the CACR precursors and the facility and stereoselectivity of the rearrangement.Using n-butyllithium as the base, the phosphonamides rearranged readily at -20 deg C with complete regioselectivity and in good yield (74-79percent).The phosphonates also showed a high level of diastereoselectivity (>95percent de) but the yield from the (Z)-2-butenyl precursor (anti product) was only 45percent.A chiral N,N'-dibenzyl-1,3,2-diazaphospholidine 12 derived from trans-1,2-cyclohexanediamine was examined.Although the CACR proceeded very cleanly (71-85percent) and with high internal selectivity (94percent de), the relative asymmetric induction was poor (16-20percent de).This was also the case for a chiral N,N'-dibenzyl-1,3,2-diazaphosphorinane 15 derived from (R,R)-1,3-diphenyl-1,3-propanediamine and N,N'-dibenzyl-1,3,2-diazaphosphepine 16 derived from 6,6'-dimethyl-2,2'-diaminobiphenyl.The characteristic features of the CACR were compared with the aryl sulfone and phosphonate versions.
- Denmark, Scott E.,Stadler, Heinz,Dorow, Roberta L.,Kim, Jung-Ho
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p. 5063 - 5079
(2007/10/02)
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- Glyoxal as Synthone, III. - A Simple Synthesis of Aminopyrroles and of Dihydropyrrolopyrroles
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The alcoholysis of diazasilacyclopentenes 2, easily obtained from glyoxaldiimines 1 with alkali metal and dichlorosilanes, gives either 3-amino-substituted pyrroles 4 or, with only small amounts of alcohol, N-substituted dihydropyrrolopyrroles 5.Reduction of 1 with hydrogen in ethanol in the presence of small amounts of a Pd/C catalyst also gives 4 and 5, together with smaller quantities of a 3,4-diaminopyrrole 7.With more of the catalyst the formation of the 1,2-diaminoethanes 6 predominates.A single-crystal X-ray diffraction study was performed for the N,N'-di-tert-butyl derivative 5a, which confirms the expected centrosymmetric structure. - Keywords: Aminopyrroles / Diaminopyrroles / 1,4-Diaza-1,3-dienes / Glyoxal / Pyrrolopyrroles
- Dieck, Heindirk tom,Verfuerth, Uwe,Diblitz, Klaus,Ehlers, Jens,Fendesak, Gert
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p. 129 - 132
(2007/10/02)
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- Reduction of diimino compounds to diamino compounds
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Organic diamines can be prepared by hydrogenating a preformed diimine in the presence of methanol and in the further presence of the tertiary alkyl mono-amine used to make the diimino compound. The diamino compounds thus obtained are useful as catalysts in the preparation of polyphenylene oxide resins.
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