85575-95-7Relevant academic research and scientific papers
Structural diversity in pyridine and polypyridine adducts of ring slipped manganocene: Correlating ligand steric bulk with quantified deviation from ideal hapticity
Cannella, Anthony F.,Dey, Suman Kr,Macmillan, Samantha N.,Lacy, David C.
, p. 5171 - 5180 (2018)
We have synthesized several new manganocene-adduct ([Cp2Mn(L)] = 1-L) complexes using pyridine and polypyridine ligands and report their molecular structures and characterization data. Consistent with other molecules in this class [(ηx-Cp)2MnLn] or [(ηx-Cp)2Mn(L-L)] (n = 1, 2; x = 1, 3, or 5), the manganese-cyclopentadienide interaction deviates from the classical ηx interactions (x = 3 or 5). Such deviations have been ascribed to steric factors and often called non-ideal hapticity. However, there is no quantification of this non-ideal hapticity and thus it is difficult to evaluate the extent of ring slippage or assign hapticity. Furthermore, the hypothesis that non-ideal hapticity in high-spin MnII complexes is induced by steric interactions has not been systematically evaluated. Therefore, we report herein a quantified scale for deviation from ideal hapticity between zero (ideal η5 interaction) and one ( η1 interaction). This quantified deviation from ideal hapticity has an empirical relationship with the ligand's steric properties, which strongly supports the premise that steric interactions cause the deviations in ionic M-Cp interactions.
Tris(2-pyridyl) Bismuthines: Coordination Chemistry, Reactivity, and Anion-Triggered Pyridyl Coupling
álvarez, Celedonio M.,Bond, Andrew D.,García-Rodríguez, Raúl,García-Romero, álvaro,Miguel, Daniel,Plajer, Alex J.,Wright, Dominic S.
supporting information, p. 7103 - 7116 (2020/06/09)
A series of new tris(2-pyridyl) bismuthine ligands of the type [Bi(2-py′)3] have been prepared, containing a range of substituents at various positions within their pyridyl rings (py′). They can act as intact ligands or, as a result of the low C-Bi bond energy, exhibit noninnocent reactivity in the presence of metal ions. Structural studies of Li+ and Ag+ complexes show that the coordination to metal ions using their pyridyl-N atoms and to anions using the Lewis acidity of their Bi(III) centers can be modified by the presence of substituents within the 2-pyridyl rings, especially at the 6- or 3-positions, which can block the donor-N or Lewis acid Bi sites. Electron withdrawing groups (like CF3 or Br) can also severely reduce their ability to act as ligands to metal ions by reducing the electron donating ability of the pyridyl-N atoms. Noninnocent character is found in the reactions with Cu+ and Cu2+, resulting in the coupling of pyridyl groups to form bipyridines, with the rate of this reaction being dependent on the anion present in the metal salts. This leads to the formation of Bi(III)/Cu(I) complexes containing hypervalent [X2Bi(2-R-py)]- (X = Cl, Br) anions. Alternatively, the tris(2-pyridyl) bismuthine ligands can act as 2-pyridyl transfer reagents, transferring 2-py groups to Au(I) and Fe(II).
A Mild Method for Electrochemical Reduction of Heterocyclic N-Oxides
Fukazawa, Yasuaki,Rubtsov, Aleksandr E.,Malkov, Andrei V.
supporting information, p. 3317 - 3319 (2020/05/25)
Deoxygenation of heteroaromatic N-oxides is commonly accomplished using chemical or enzymatic methods. In this work, we report on an expedient protocol for electrochemical reduction of pyridine N-oxide derivatives under mild conditions. A diverse range of mono- and bis N-oxides were converted into the corresponding nitrogen bases in good yields. Importantly, the method is highly selective towards N-oxides and tolerates challenging halo and nitro substituents in the heteroaromatic ring.
Mechanistic insights into the potassium: Tert -butoxide-mediated synthesis of N-heterobiaryls
Stephens, David E.,Lakey-Beitia, Johant,Burch, Jessica E.,Arman, Hadi D.,Larionov, Oleg V.
supporting information, p. 9945 - 9948 (2016/08/11)
We report herein that symmetrical and non-symmetrical N-heterobiaryls are produced by a potassium tert-butoxide-mediated dimerization of heterocyclic N-oxides. The reaction is scalable and transition metal-free, and can be carried out under thermal and microwave conditions. Preliminary mechanistic studies point to the involvement of radical anionic intermediates arising from the N-oxide substrates and potassium tert-butoxide.
Ni(II) complexes with ligands derived from phenylpyridine, active for selective dimerization and trimerization of ethylene
Chandran, Deepak,Lee, Kyeong Mi,Chang, Hyuk Chul,Song, Ga Young,Kim, Il,Lee, Ji-Eun,Suh, Hongsuk
, p. 8 - 13,6 (2020/08/20)
An electrophilic substitution-carbonylation reaction on phenylpyridine based on the concept of 'umpolung' was used to prepare a series of pyridine based carbonyl compounds and bispyridine derivatives. The key intermediate which enhances this reaction is a base aggregate formed by the association of BuLi with lithium 2-dimethylaminoethanolate (LiDMAE) which is stabilized in nonpolar solvents. The presence of polar chelating amides that are used as acyl donors was found to collapse the superbase aggregates liberating nucleophilic 'free' BuLi. These nucleophiles lead a classical nucleophilic reaction to introduce butyl tails on the pre-ligand molecules. Pyridine carbonyl compounds produced by these electrophilic substitution-carbonylation reactions, on treatment with 2,6-diisopropylaniline and (DME)NiBr2 in glacial acetic acid at reflux temperature, gave Ni(II) complexes in good yields in a one pot protocol. These complexes are active toward ethylene, producing selective dimerization and trimerization products.
Synthesis, characterisation and application of iridium(III) photosensitisers for catalytic water reduction
Gaertner, Felix,Cozzula, Daniela,Losse, Sebastian,Boddien, Albert,Anilkumar, Gopinatan,Junge, Henrik,Schulz, Thomas,Marquet, Nicolas,Spannenberg, Anke,Gladiali, Serafino,Beller, Matthias
body text, p. 6998 - 7006 (2011/07/29)
The synthesis of novel, monocationic iridium(III) photosensitisers (Ir-PSs) with the general formula [IrIII(C^N)2(N^N)]+ (C^N: cyclometallating phenylpyridine ligand, N^N: neutral bidentate ligand) is described. The structures obtained were examined by cyclic voltammetry, UV/Vis and photoluminescence spectroscopy and X-ray analysis. All iridium complexes were tested for their ability as photosensitisers to promote homogeneously catalysed hydrogen generation from water. In the presence of [HNEt 3][HFe3(CO)11] as a water-reduction catalyst (WRC) and triethylamine as a sacrificial reductant (SR), seven of the new iridium complexes showed activity. [Ir(6-iPr-bpy)(ppy)2]PF 6 (bpy: 2,2′-bipyridine, ppy: 2-phenylpyridine) turned out to be the most efficient photosensitiser. This complex was also tested in combination with other WRCs based on rhodium, platinum, cobalt and manganese. In all cases, significant hydrogen evolution took place. Maximum turnover numbers of 4550 for this Ir-PS and 2770 for the Fe WRC generated in situ from [HNEt 3][HFe3(CO)11] and tris[3,5- bis(trifluoromethyl)phenyl]phosphine was obtained. These are the highest overall efficiencies for any Ir/Fe water-reduction system reported to date. The incident photon to hydrogen yield reaches 16.4 % with the best system. Copyright
A direct route to 6,6′-disubstituted-2,2′-bipyridines by double Diels-Alder/retro Diels-Alder reaction of 5,5′-bi-1,2,4-triazines
Branowska, Danuta
, p. 274 - 278 (2007/10/03)
Inverse electron demand Diels-Alder reaction of functionalized 5,5′-bi-1,2,4-triazines with bicyclo[2.2.1]hepta-2,5-diene in boiling p-cymene leads to a range of 6,6′-disubstituted-2,2′-bipyridines in good yield.
The use of Ni(CO)2(PPh3)2 in aryl and pyridyl coupling reactions
Leadbeater, Nicholas E.,Resouly, Sarah M.
, p. 4243 - 4246 (2007/10/03)
The zerovalent nickel complex Ni(CO)2(PPh3)2 has been used for the coupling of aryl halides to form biaryls and for the coupling of bromopyridines to form polypyridines. The effects of solvent, halide and substituents have also been investigated.
Unusual formation of 5-halo-2,2'-bipyridyls by treatment of tris(2-pyridyl)phosphine derivatives with halogens
Uchida,Kajita,Kawasaki,Oae
, p. 4077 - 4080 (2007/10/02)
Reaction of tris(2-pyridyl)phosphine with chlorine in dichloromethane or acetonitrile gave chlorotris(2-pyridyl)phosphonium chloride which afforded a coupling product, 2,2'-bipyridyl, by treating with dilute HCl. Treatment of tris(2-pyridyl)phosphine or tris(2-pyridyl)phosphine oxide with chlorine or bromine in methanol gave unusual 5-halo-2,2'-bipyridyl as a major coupling product. This is undoubtedly an electrophilic substitution on a pyridyl ring in the pentacovalent phosphorane.
