- Two octahedral σ-borane metal (MnI and RuII) complexes containing a tripod κ3N,H,H-ligand: Synthesis, structural characterization, and theoretical topological study of the charge density
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Theoretical electron density (QTAIM) studies in the gas-phase have shown that the attachment of the BH3 group to the metal atom in complexes [Mn(κ3N,H,H-iPr2bzamBH3)(CO)3] (1) and [Ru(η5-C5Me5)(κ3N,H,H-iPr2bzamBH3)] (2) (HiPr2bzamBH3 = N-trihydridoborane-N,N′-bis(isopropyl) benzamidine) is symmetric in the latter but asymmetric in the former, and involves two B–H–metal interactions that are intermediate between κ1H (Shimoi type) and κ2H,B (agostic type). The herein reported results, coupled to previous ones on related complexes having a similar tripod κ3N,H,H-borane ligand, show that the bonding similarities and differences within each particular M(μ-H)2B moiety are not related to the type of metal atom, nor even to its coordination geometry, but mainly to the molecular symmetry.
- Van der Maelen, Juan F.,Brugos, Javier,García-álvarez, Pablo,Cabeza, Javier A.
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- Monometallic and bimetallic titanium κ1-Amidinate complexes as olefin polymerization catalysts
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A series of cyclopentadienyl-?1-amidinate titanium complexes Cp?Ti{NC(ArR)NiPr2}Me2 (ArR = 4-C6H4R, where R = H (1-Me), CF3 (5-Me), tBu (6-Me), or NMe2 (7-Me)) with different para-substituents in the amidinate ligand were synthesized and structurally characterized, along with three bimetallic analogues: 1,4-C6H4{C(NiPr2)N}2{Cp?TiMe2}2 (2-Me), 1,3-C6H4{C(NiPr2)N}2{Cp?TiMe2}2 (3-Me), and CH2{1,4-C6H4-C(NiPr2)N}2{Cp?TiMe2}2 (4-Me). 13C NMR spectroscopy, density function theory, and the quantum theory of atoms-in-molecules were used to evaluate the donor ability of the various NC(Ar R)NiPr2 ligands and the influence of the ArR group para-substituents. Reactions of 1-Me and certain homologues, as well as 2-Me, with borate and borane reagents [CPh3][BArF4] (ArF = C6F5), BArF3, in the absence or presence of Lewis bases or polar unsaturated substrates were carried out, forming adducts and migratory insertion products such as [Cp?Ti{NC(Ph)NiPr2}Me(THF)][BArF4], [Cp?Ti{NC(Ph)NiPr2}{MeC(NiPr)2}][BArF4], and [1,4-C6H4{C(NiPr2)N}2{Cp?Ti{MeC(NiPr)2}2][BArF4]2. Detailed olefin copolymerization studies for forming EPDM from ethylene, propylene, and certain dienes were carried out with mono- and bimetallic catalysts and borate and borane activators. Catalyst-activator effects on polymerization productivity and polymer composition relationships were mapped. Bimetallic catalysts 2 and 3 showed cooperative effects based on electronic factors, leading to enhanced propene incorporation, but unfavorable steric effects gave lower diene content. Related but less significant electronic effects on propene affinity were found for the monometallic catalysts Cp?Ti{NC(ArR)NiPr2}Me2 as the ArR moiety para-substituents were varied.
- Collins, Richard A.,Russell, Adam F.,Scott, Richard T. W.,Bernardo, Raffaele,Van Doremaele, Gerard H. J.,Berthoud, Alexandra,Mountford, Philip
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- Sulfated tungstate catalyzed activation of nitriles: addition of amines to nitriles for synthesis of amidines
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An efficient and mild method for the synthesis of amidines by direct nucleophilic addition of amines to nitriles using sulfated tungstate as heterogeneous catalyst is described. Highlight of the method is its applicability for the synthesis of amidines using a wide variety of amines including ammonia as ammonium acetate and nitriles. Catalyst is mildly acidic, stable, easy to prepare and separate from the reaction mass.
- Veer, Sachin D.,Katkar, Kamlesh V.,Akamanchi, Krishnacharya G.
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supporting information
p. 4039 - 4043
(2016/08/18)
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- Stereoselective Synthesis of trans-2-Aryl-3-(2-pyridyl)aziridines from an α-Silyl Carbanion
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Five para-substituted benzaldehyde oxime O-methyl ethers (3) reacted with 2-(trimethylsilylmethyl)pyridine (1) in the presence of lithium di-isopropylamide (LDA) in tetrahydrofuran to give the corresponding trans-2-aryl-3-(2-pyridyl)aziridines (4) in high yield (80, 85, 60, 58, and 74percent, respectively), with small amounts of (Z)-1-amino-1-aryl-2-(2-pyridyl)ethenes (5), and N',N'-di-isopropylbenzamidines (7) as byproducts.The yields of compounds (4) and (5) and their ratio were considerably influenced by experimental conditions (especially molar ratio and the addition method of the reactants).When treated with LDA, compounds (3) were quantitatively converted into benzonitriles, which reacted with anion (2) to give enamines (5) after elimination of a trimethylsilyl group from the corresponding N-trimethylsilyl derivatives, or with additional LDA to give the benzamidine (7); aziridines (4) were not transformed into enamines (5) by the action of LDA.On the basis of these results, a reaction mechanism has been discussed for the formation of compounds (4).
- Konakahara, Takeo,Matsuki, Masayuki,Sugimoto, Shinji,Sato, Kenji
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p. 1489 - 1494
(2007/10/02)
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