89488-29-9Relevant articles and documents
Preparation of substituted alkoxypyridines via directed metalation and metal-halogen exchange
Bori, Ibrahim D.,Comins, Daniel L.
, p. 57 - 72 (2021/03/15)
Several halo-substituted alkoxypyridines were prepared and subjected to directed metalation and metal-halogen exchange reactions. The studies resulted in useful methods for synthesis of numerous substituted pyridines via regioselective lithiation, magnesation and halogen dance reactions.
Photocatalytic CO2 Reduction by Trigonal-Bipyramidal Cobalt(II) Polypyridyl Complexes: The Nature of Cobalt(I) and Cobalt(0) Complexes upon Their Reactions with CO2, CO, or Proton
Shimoda, Tomoe,Morishima, Takeshi,Kodama, Koichi,Hirose, Takuji,Polyansky, Dmitry E.,Manbeck, Gerald F.,Muckerman, James T.,Fujita, Etsuko
, p. 5486 - 5498 (2018/05/17)
The cobalt complexes CoIIL1(PF6)2 (1; L1 = 2,6-bis[2-(2,2′-bipyridin-6′-yl)ethyl]pyridine) and CoIIL2(PF6)2 (2; L2 = 2,6-bis[2-(4-methoxy-2,2′-bipyridin-6′-yl)ethyl]pyridine) were synthesized and used for photocatalytic CO2 reduction in acetonitrile. X-ray structures of complexes 1 and 2 reveal distorted trigonal-bipyramidal geometries with all nitrogen atoms of the ligand coordinated to the Co(II) center, in contrast to the common six-coordinate cobalt complexes with pentadentate polypyridine ligands, where a monodentate solvent completes the coordination sphere. Under electrochemical conditions, the catalytic current for CO2 reduction was observed near the Co(I/0) redox couple for both complexes 1 and 2 at E1/2 = -1.77 and -1.85 V versus Ag/AgNO3 (or -1.86 and -1.94 V vs Fc+/0), respectively. Under photochemical conditions with 2 as the catalyst, [Ru(bpy)3]2+ as a photosensitizer, tri-p-tolylamine (TTA) as a reversible quencher, and triethylamine (TEA) as a sacrificial electron donor, CO and H2 were produced under visible-light irradiation, despite the endergonic reduction of Co(I) to Co(0) by the photogenerated [Ru(bpy)3]+. However, bulk electrolysis in a wet CH3CN solution resulted in the generation of formate as the major product, indicating the facile production of Co(0) and [Co-H]n+ (n = 1 and 0) under electrochemical conditions. The one-electron-reduced complex 2 reacts with CO to produce [Co0L2(CO)] with νCO = 1894 cm-1 together with [CoIIL2]2+ through a disproportionation reaction in acetonitrile, based on the spectroscopic and electrochemical data. Electrochemistry and time-resolved UV-vis spectroscopy indicate a slow CO binding rate with the [CoIL2]+ species, consistent with density functional theory calculations with CoL1 complexes, which predict a large structural change from trigonal-bipyramidal to distorted tetragonal geometry. The reduction of CO2 is much slower than the photochemical formation of [Ru(bpy)3]+ because of the large structural changes, spin flipping in the cobalt catalytic intermediates, and an uphill reaction for the reduction to Co(0) by the photoproduced [Ru(bpy)3]+.
4,4″-disubstituted terpyridines and their homoleptic FeII complexes
Harzmann, Gero D.,Neuburger, Markus,Mayor, Marcel
, p. 3334 - 3347 (2013/07/26)
A novel synthetic route to 4,4″-disubstituted-2,2′:6′, 2″-terpyridine ligands by Suzuki-Miyaura cross-coupling was elaborated by synthesizing compounds 4a-5c. The considerable stability of 4-substituted lithium triisopropyl 2-pyridylborates 2a-c, which are less prone to protodeboronation than similarly functionalized neutral boronic acid derivatives, enabled this synthetic route. The terpyridine core structure was further functionalized by exposing 4,4″-dichloroterpyridine (4b) to Suzuki coupling conditions to yield 4,4″-diarylterpyridines 5a-c. Homoleptic FeII complexes 8a-f of the reported terpyridine ligands were formed quantitatively, which demonstrates the lack of steric repulsion of substituents at the 4- and 4″-positions during complexation. The solid-state structures of particular ligands and FeII complexes were analyzed by single-crystal X-ray crystallography. UV/Vis absorption data for the Fe II complexes are also provided to complement the results reported here. A novel synthetic route to terpyridine ligands is reported. Pyridine building blocks are interlinked by Suzuki-Miyaura cross-coupling reactions. The potential of the method is demonstrated by assembling the 4,4″- disubstituted terpyridine ligands shown, which are subsequently converted into their homoleptic FeII complexes. Copyright
