142946-79-0Relevant articles and documents
Synthesis of bis(trifluoromethyl)-2,2'-bipyridines by nickel catalysed homocoupling reactions
Chan,Tse
, p. 1929 - 1934 (1993)
Bis(trifluoromethyl)-2,2'-bipyridines have been synthesized in moderate yields by nickel or palladium catalysed homocoupling of 2-chloro-(trifluoromethyl)pyridines.
Photoacidic and Photobasic Behavior of Transition Metal Compounds with Carboxylic Acid Group(s)
O'Donnell, Ryan M.,Sampaio, Renato N.,Li, Guocan,Johansson, Patrik G.,Ward, Cassandra L.,Meyer, Gerald J.
, p. 3891 - 3903 (2016)
Excited state proton transfer studies of six Ru polypyridyl compounds with carboxylic acid/carboxylate group(s) revealed that some were photoacids and some were photobases. The compounds [RuII(btfmb)2(LL)]2+, [RuII(dtb)2(LL)]2+, and [RuII(bpy)2(LL)]2+, where bpy is 2,2′-bipyridine, btfmb is 4,4′-(CF3)2-bpy, and dtb is 4,4′-((CH3)3C)2-bpy, and LL is either dcb = 4,4′-(CO2H)2-bpy or mcb = 4-(CO2H),4′-(CO2Et)-2,2′-bpy, were synthesized and characterized. The compounds exhibited intense metal-to-ligand charge-transfer (MLCT) absorption bands in the visible region and room temperature photoluminescence (PL) with long τ > 100 ns excited state lifetimes. The mcb compounds had very similar ground state pKa's of 2.31 ± 0.07, and their characterization enabled accurate determination of the two pKa values for the commonly utilized dcb ligand, pKa1 = 2.1 ± 0.1 and pKa2 = 3.0 ± 0.2. Compounds with the btfmb ligand were photoacidic, and the other compounds were photobasic. Transient absorption spectra indicated that btfmb compounds displayed a [RuIII(btfmb-)L2]2+? localized excited state and a [RuIII(dcb-)L2]2+? formulation for all the other excited states. Time dependent PL spectral shifts provided the first kinetic data for excited state proton transfer in a transition metal compound. PL titrations, thermochemical cycles, and kinetic analysis (for the mcb compounds) provided self-consistent pKa? values. The ability to make a single ionizable group photobasic or photoacidic through ligand design was unprecedented and was understood based on the orientation of the lowest-lying MLCT excited state dipole relative to the ligand that contained the carboxylic acid group(s).
Improved synthesis of electron deficient bipyridines
Li, Hao,Oppenheimer, Jossian,Smith, Milton R.,Maleczka, Robert E.
, p. 2231 - 2232 (2016)
Symmetric bipyridines commonly serve as ligands for various types of catalytic processes. Nickel catalyzed Ullmann couplings are often used to prepare such bipyridines, however for electron deficient substrates low conversions and/or yields are often reported. We herein report an improved synthesis of trifluoromethyl substituted bipyridines using stoichiometric amounts of Zn(0), NiCl2·6H2O, and Ph3P. This modified procedure enables a >20 fold improvement over the previously reported yield for the synthesis of 4,4′,5,5′-tetrakis(trifluoromethyl)-2,2′-bipyridine.
Structural and spectroscopic studies of reduced [Re(bpy-R)(CO) 3]-1 species relevant to CO2 reduction
Benson, Eric E.,Grice, Kyle A.,Smieja, Jonathan M.,Kubiak, Clifford P.
, p. 229 - 234 (2013)
Spectroscopic and structural comparisons are made between the rhenium anions with bpy-R ligands spanning a wide range of electron-withdrawing and donating abilities (R = CF3, H, Me, tBu, OMe). The synthesis and characterization of the rhenium anions [Re(bpy-R)(CO)3]-1 (bpy-R = 4,4′-disubstitued- 2,2′-bipyridine; R = CF3, Me, OMe) are reported. The anions [Re(bpy-R)(CO)3]1 (R = Me and OMe) were structurally characterized. X-ray characterization of [Re(bpy-CF3)(CO)3]-1 was unsuccessful. However, the structure of a mono-reduced complex, [Re(bpy-CF3)(CO) 3Cl][K(18-crown-6)] was obtained. This compound is a rare example of a structurally characterized 19e- intermediate formed in the chemical and electrochemical reduction of a Re(bpy-R)(CO)3Cl species.
A Systematic Study of the Effects of Complex Structure on Aryl Iodide Oxidative Addition at Bipyridyl-Ligated Gold(I) Centers
Bower, John F.,Cadge, Jamie A.,Russell, Christopher A.
supporting information, p. 24976 - 24983 (2021/10/20)
A combined theoretical and experimental approach has been used to study the unusual mechanism of oxidative addition of aryl iodides to [bipyAu(C2H4)]+ complexes. The modular nature of this system allowed a systematic assessment of the effects of complex structure. Computational comparisons between cationic gold and the isolobal (neutral) Pd0 and Pt0 complexes revealed similar mechanistic features, but with oxidative addition being significantly favored for the group 10 metals. Further differences between Au and Pd were seen in experimental studies: studying reaction rates as a function of electronic and steric properties showed that ligands bearing more electron-poor functionality increase the rate of oxidative addition; in a complementary way, electron-rich aryl iodides give faster rates. This divergence in mechanism compared to Pd suggests that Ar?X oxidative addition with Au can underpin a broad range of new or complementary transformations.
Discovery and Elucidation of Counteranion Dependence in Photoredox Catalysis
Farney, Elliot P.,Chapman, Steven J.,Swords, Wesley B.,Torelli, Marco D.,Hamers, Robert J.,Yoon, Tehshik P.
, p. 6385 - 6391 (2019/05/02)
Over the past decade, there has been a renewed interest in the use of transition metal polypyridyl complexes as photoredox catalysts for a variety of innovative synthetic applications. Many derivatives of these complexes are known, and the effect of ligand modifications on their efficacy as photoredox catalysts has been the subject of extensive, systematic investigation. However, the influence of the photocatalyst counteranion has received little attention, despite the fact that these complexes are generally cationic in nature. Herein, we demonstrate that counteranion effects exert a surprising, dramatic impact on the rate of a representative photocatalytic radical cation Diels-Alder reaction. A detailed analysis reveals that counteranion identity impacts multiple aspects of the reaction mechanism. Most notably, photocatalysts with more noncoordinating counteranions yield a more powerful triplet excited state oxidant and longer radical cation chain length. It is proposed that this counteranion effect arises from Coulombic ion-pairing interactions between the counteranion and both the cationic photoredox catalyst and the radical cation intermediate, respectively. The comparatively slower rate of reaction with coordinating counteranions can be rescued by using hydrogen-bonding anion binders that attenuate deleterious ion-pairing interactions. These results demonstrate the importance of counteranion identity as a variable in the design and optimization of photoredox transformations and suggest a novel strategy for the optimization of organic reactions using this class of transition metal photocatalysts.
Anti-Markovnikov Hydroamination of Unactivated Alkenes with Primary Alkyl Amines
Miller, David C.,Ganley, Jacob M.,Musacchio, Andrew J.,Sherwood, Trevor C.,Ewing, William R.,Knowles, Robert R.
supporting information, p. 16590 - 16594 (2019/11/03)
We report here a photocatalytic method for the intermolecular anti-Markovnikov hydroamination of unactivated olefins with primary alkyl amines to selectively furnish secondary amine products. These reactions proceed through aminium radical cation (ARC) intermediates and occur at room temperature under visible light irradiation in the presence of an iridium photocatalyst and an aryl thiol hydrogen atom donor. Despite the presence of excess olefin, high selectivities are observed for secondary over tertiary amine products, even though the secondary amines are established substrates for ARC-based olefin amination under similar conditions.
