872-53-7Relevant articles and documents
Two-dimensional (2d) correlation analysis and the search for intermediates: A strictly mathematical approach to an important mechanistic question
Xu, Qisong,Guo, Liangfeng,Dinh, Tung Nguyen,Cheong, Angie,Garland, Marc
, p. 3588 - 3599 (2015)
In situ spectroscopic studies of metal-mediated syntheses of new and previously unstudied systems are being increasingly used to better understand speciation and mechanistic aspects. These types of experiments give rise to an interesting question: namely, can one deduce from in situ data alone, and with no a priori chemical knowledge (i.e. chemical assignments), which pure component spectral estimates correspond to intermediates? In the present contribution, a statistical 2D correlation analysis is introduced to solve this problem for unicyclic catalytic systems. Such a methodological development achieves two goals: (1) it allows the experimentalist to concentrate on the most meaningful information at the outset of a new exploratory study (focus on the species directly associated with the catalysis), and (2) it helps to free the experimentalist from chemical bias and prejudice, i.e. believing that a specific organometallic species has to be an intermediate due to one or more chemical arguments, when in fact it may be just a side product or spectator species in the metal-mediated synthesis. The 2D correlation analysis is first tested with a numerically simulated data set and then with a real in situ FTIR data set from an unmodified rhodium-catalyzed hydroformylation. The resulting statistical 2D correlation analysis provides a clear and correct answer.
Concurrent synergism and inhibition in bimetallic catalysis: Catalytic binuclear elimination, solute-solute interactions and a hetero-bimetallic hydrogen-bonded complex in Rh-Mo hydroformylations
Li, Chuanzhao,Cheng, Shuying,Tjahjono, Martin,Schreyer, Martin,Garland, Marc
, p. 4589 - 4599 (2010)
Hydroformylations of cyclopentene and 3,3-dimethylbut-1-ene were performed using both Rh4(CO)12 and (η5-C 5H5)Mo(CO)3H as precursors in n-hexane at 298 K. Both stoichiometric and catalytic hydroformylations were conducted as well as isotopic labeling experiments. Six organometallic pure component spectra were recovered from the high-pressure FTIR experiments, namely the known species Rh4(CO)12, (η5-C5H 5)Mo(CO)3H, RCORh(CO)4, and the new heterobimetallic complexes RhMo(CO)7(η5-C 5H5), a weak hydrogen bonded species (η5- C5H5)Mo(CO)3H-C5H 9CORh(CO)4, and a substituted RhMo(CO) 7-y(η5-C5H5)Ly, where y = 1 or 2 and L = (--C5H8). The main findings were (1) catalytic binuclear elimination (CBER) occurs between (η5-C 5H5)Mo(CO)3H and RCORh(CO)4 resulting in aldehyde and RhMo(CO)7(η5-C 5H5), and this mechanism is responsible for ca. 10% of the product formation; (2) molecular hydrogen is readily activated by the new heterobimetallic complex(es); (3) FTIR and DFT spectroscopic evidence suggests that the weak hydrogen bonded species (η5-C5H 5)Mo(CO)3H-C5H9CORh(CO)4 has an interaction of the type η5-C5H4-HO - C; and (4) independent physicochemical experiments for volumes of interaction confirm that significant solute-solute interactions are present. With respect to the efficiency of the catalytic cycle, the formation of a weak (η5-C5H5)Mo(CO)3H-C 5H9CORh(CO)4 complex results in a significant decrease in the measured turnover frequency (TOF) and is the primary reason for the inhibition observed in the bimetallic catalytic hydroformylation. Such hydrogen bonding through the η5-C5H5 ring might have relevance to inhibition observed in other catalytic metallocene systems. The present catalytic system is an example of concurrent synergism and inhibition in bimetallic homogeneous catalysis.
Facile One-Pot Transformation of Primary Alcohols into 3-Aryl- and 3-Alkyl-isoxazoles and -pyrazoles
Kobayashi, Eiji,Togo, Hideo
, p. 3723 - 3735 (2019/09/30)
Various primary alcohols were smoothly transformed into 3-aryl- and 3-alkylisoxazoles in good yields in one pot by successive treatment with PhI(OAc) 2 in the presence of TEMPO, NH 2 OH, and then NCS, followed by reaction with alkynes in the presence of Et 3 N. Similarly, various primary alcohols were smoothly transformed into 3-aryl- and 3-alkylpyrazoles in good yields in one pot by successive treatment with PhI(OAc) 2 in the presence of TEMPO, PhNHNH 2, and then NCS and decyl methyl sulfide, followed by reaction with alkynes in the presence of Et 3 N. Thus, both 3-aryl- and 3-alkylisoxazoles, and 3-aryl- and 3-alkylpyrazoles could be prepared from readily available primary alcohols in one pot under transition-metal-free conditions.
Maximizing the Number of Interfacial Sites in Single-Atom Catalysts for the Highly Selective, Solvent-Free Oxidation of Primary Alcohols
Li, Tianbo,Liu, Fei,Tang, Yan,Li, Lin,Miao, Shu,Su, Yang,Zhang, Junying,Huang, Jiahui,Sun, Hui,Haruta, Masatake,Wang, Aiqin,Qiao, Botao,Li, Jun,Zhang, Tao
supporting information, p. 7795 - 7799 (2018/06/26)
The solvent-free selective oxidation of alcohols to aldehydes with molecular oxygen is highly attractive yet challenging. Interfacial sites between a metal and an oxide support are crucial in determining the activity and selectivity of such heterogeneous catalysts. Herein, we demonstrate that the use of supported single-atom catalysts (SACs) leads to high activity and selectivity in this reaction. The significantly increased number of interfacial sites, resulting from the presence of individually dispersed metal atoms on the support, renders SACs one or two orders of magnitude more active than the corresponding nanoparticle (NP) catalysts. Lattice oxygen atoms activated at interfacial sites were found to be more selective than O2 activated on metal NPs in oxidizing the alcohol substrate. This work demonstrates for the first time that the number of interfacial sites is maximized in SACs, providing a new avenue for improving catalytic performance by developing appropriate SACs for alcohol oxidation and other reactions occurring at metal–support interfacial sites.
