2116-62-3Relevant articles and documents
Photochemistry of chromium arene tricarbonyl complexes with tethered pyridinyl and propenyl groups: Investigations of the effect of ring size on chelate formation, structure, and linkage isomerization
Duke, Charles B.,Letterman, Roger G.,Johnson, Jermaine O.,Barr, James W.,Hu, Songnan,Ross, Charles R.,Webster, Charles Edwin,Burkey, Theodore J.
, p. 485 - 497 (2014)
Chromium arene tricarbonyl complexes with tethered pyridinyl groups [Cr{η6-C6H5(CH2) n(2-Py)}(CO)3] (4-6) (2-Py = 2-pyridinyl, n = 1-3, respectively) were synthesized and irradiated to form the chelates [Cr{η6-C6H5(CH2) n(2-Py)-κN}(CO)2] (7-9). Studies examined the effect of ring size and structure on chromophore λmax, stability, and photosensitivity, which are factors important for photochromes based on linkage isomerization of tethered functional groups. The studies also include [Cr{η6-C6H5CH(2-Py)CH2CH=CH 2}(CO)3] (3), which has a bifunctional tether of propenyl and pyridinyl groups, and irradiation produces the linkage isomers [Cr{η6-C6H5(CH(2-Py)CH2CH= CH2)-κN}(CO)2] (1) and [Cr{η6-C 6H5(CH(2-Py)CH2CH=CH2) (η2-CH=CH2)}(CO)2] (2). X-ray crystal structures for 7-9 show that the dihedral angle between the coordinated pyridinyl groups and the phenyl-chromium centroid increases from 1 to 73 (n = 1-3, respectively). The experimental and TDDFT computed optical changes accompanying an increase in the dihedral angle are modest and not monotonic for 7-9 due to structural changes inherent in the chelate rings. An increase in Cr-N bond lengths and decrease in their bond energies were observed experimentally and computationally for the series of 7-9. The quantum yields for formation of the five-, six-, and seven-membered chelate rings during the conversion of 4-6 to 7-9, respectively, were within experimental error for that observed for conversion of 10 [Cr{η6-C6H6}(CO) 3] with free pyridine to 11 [Cr{η6-C6H 6}(C5H5N-κN)(CO)2], indicating that the product-determining step precedes chelation. The enthalpies for chelation of 4-6 to 7-9 were determined independently by photoacoustic calorimetry and DFT computations. The computationally derived mechanism for thermal isomerization of 1 to 2 indicates that the transition state is a dissociative interchange with a free energy of activation of 27.9 kcal mol -1 (1 → 2), a result consistent with an experimentally bistable photochrome. The results indicate which tether properties are important for optimizing photochrome performance.
An improved method for aromatic hydroxylation with heteroaromatic oxides
Serra-Errante, Guido,Sammes, Peter G.
, p. 573 - 574 (1975)
Photolysis of the boron trifluoride complex of pyridine-N-oxide in benzene gives a higher yield of phenol than photolysis of pyridine-N-oxide alone; with some intramolecular models, intramolecular hydroxylation can be achieved.
C2-selective alkylation of pyridines by rhodium–aluminum complexes
Aso, Koki,Hara, Naofumi,Li, Qiao-Zhi,Nakao, Yoshiaki,Sakaki, Shigeyoshi
supporting information, (2021/08/06)
A C2- and mono-selective alkylation of various pyridines and azines with unactivated alkenes and vinylarenes using a heterobimetallic Rh–Al catalyst is reported. The use of aliphatic alkenes exclusively affords the linear alkylation products, while vinylarenes mainly afford branched alkylation products. The details of the reaction mechanism are revealed by DFT calculations: the reductive elimination of the products is rate-determining, which is consistent with the experimental results. The origin of the linear/branched selectivity is elucidated based on deformation/interaction analysis.
An Annelated Mesoionic Carbene (MIC) Based Ru(II) Catalyst for Chemo- And Stereoselective Semihydrogenation of Internal and Terminal Alkynes
Bera, Jitendra K.,Choudhury, Joyanta,Das, Shubhajit,Dutta, Indranil,Pati, Swapan K.,Saha, Sayantani,Yadav, Suman
, p. 3212 - 3223 (2020/10/02)
The catalytic utility of [RuL1(CO)2I2] (1), containing an annelated π-conjugated imidazo-naphthyridine-based mesoionic carbene (MIC) ligand (L1), is evaluated for E-selective alkyne semihydrogenation. The precatalyst 1, in combination with 2 equiv of AgBArF, semihydrogenates a broad range of internal alkynes with molecular hydrogen (5 bar) in water. (E)-Alkenes are accessed in high yields, and a number of reducible functional groups are tolerated. A chelate MIC ligand and two cis carbonyls provide a well-defined platform at the Ru center for hydrogenation and isomerization. The loss of two iodides and the presence of two carbonyls render the Ru center electron deficient and thus the formation of metal vinylidenes with terminal alkynes is avoided. This is leveraged for the semihydrogenation of terminal alkynes by the same catalytic system in isopropyl alcohol. Reaction profile, isomerization, kinetic, and DFT studies reveal initial alkyne hydrogenation to a (Z)-alkene, which further isomerizes to an (E)-alkene via metal-catalyzed Z → E isomerization.
Aqueous phase semihydrogenation of alkynes over Ni-Fe bimetallic catalysts
Awasthi, Mahendra K.,Barman, Sudipta Roy,Behrens, Silke,Rai, Rohit K.,Singh, Sanjay K.,Singh, Vipin K.
, p. 4968 - 4980 (2020/08/19)
Bimetallic Ni-Fe catalysts (Ni/Fe, 1?:?1, 1?:?3, and 3?:?1) are synthesized and explored for their catalytic activity in semihydrogenation of internal alkynes using H2 gas in water-ethanol solution. Our findings revealed that over the Ni1Fe3 catalyst a high diastereoselectivity for Z-alkenes with a high conversion for a wide range of internal alkynes can be achieved at moderate reaction temperature (40 °C). Notably, the selectivity for the Z-alkenes is enhanced in the presence of n-butyl amine as an additive. Deuterium labeling experiments evidenced that H2 gas becomes dissociated homolytically over the catalyst surface to hydrogenate alkynes to alkenes. Synthesized catalysts were successfully characterized by HR-TEM, SEM, XPS, EDS, P-XRD and H2-TPD.
