Nuclear magnetic resonance spectroscopy catalysts

Hunger, M. and Wang, W. (2006) Characterization of solid catalysts in the functioning state by Nuclear Magnetic Resonance spectroscopy. Adv. Catal.,... 

Characterization of Solid Catalysts in the Functioning State by Nuclear Magnetic Resonance Spectroscopy... 

Hunger and Wang provide an account of advances in the characterization of solid catalysts in the functioning state by nuclear magnetic resonance spectroscopy. Examples include investigations of zeolite-catalyzed reactions with isotopic labels that allow characterization of transition states and reaction pathways as well as characterization of organic deposits, surface complexes, and reaction intermediates formed in catalyst pores. 

In the case of H-CBS, this catalyst could be prepared by mixing diphenylprolinol with borane-THF (tetrahydrofuran) or borane dimethylsulfide. Despite numerous efforts in many groups to isolate or even characterize H-CBS by nuclear magnetic resonance spectroscopy, all attempts have been unsuccessful. H-CBS is used in situ, and good results can be obtained in many cases. 

T.M. Duncan, P. Winslow, and A.T. Bell, The Characterization of Carbonaceous Species on Ruthenium Catalysts with C Nuclear Magnetic Resonance Spectroscopy, J. Catal. 93 (1985) 1. 

The uses of the aza-erown macrocycles are multiplying as shown above. New research is reported almost daily. The titles of a few recent articles are instructive (1) Macrocyclic Polyamines [IbjN, and [21]N4 Synthesis and a Study of Their ATP Complexation by P Nuclear Magnetic Resonance Spectroscopy (Prakash et al., 1991) (2) Removal of Dyes from Solution with the Macrocyclic Ligands (Buschmann et al., 1991a, 1991b) (3) Iron-Cyclam Complexes as Catalysts for the Epoxidation of Olefins by 30% Aqueous Hydrogen Peroxide in Acetonitrile and Methanol (Nam et al.,... 

The structures of the polymers resulting from the cationic polymerization of 4-methyl-l-pentene with an AICI3 catalyst in CjHjCl solvent at -78, -50, and +5°C were investigated by nuclear magnetic resonance spectroscopy (Mizuno and Kawachi, 1992). The main product of the reaction is structurally similar to an ethylene isobutylene alternating copolymo-. 

Haw, J.F., Richardson, B.R., Oshiro, I.S., Lazo, N.D. and Speed, J.A. (1989), Reactions of propene on zeolite HY catalyst studied by in situ variable - temperature solid-state nuclear magnetic resonance spectroscopy, J. Am. Chem. Soc. Ill, 2052-2058. 

The study of ethylene and propylene copolymerisation, on vanadium and titanium catalysts of various compositions [70], led to the conclusion that studied catalytic systems contain two or three types of AC. This conclusion has been made as a result of the analysis of the MWD curves, carbon nuclear magnetic resonance spectroscopy analysis, and copolymers composition fractionation data. The analysis of a large number of copolymer fractions, produced by their dissolution in several solvents at various temperatures, has indicated the existence of several types of AC different both in stereospecificity and in reactivity. According to the authors of [70], a combination of copolymer fractionation results with gel chromatography data indicates the presence of two or three types of AC. 

In order to rank performance of catalysts in copol)unerization with respect to comonomer incorporation and comonomer sequence distribution, copolymerization parameters have proven to be very useful. They are determined by means of nuclear magnetic resonance spectroscopy (NMR copolymer sequence analysis) taking into account the Markovian statistics of chain growth, as reviewed by Randall [4], Galimberti and coworkers [5] described the analysis of EPM prepared by means of... 

Mizuno, A. Tsutsui, T. Kashiwa, N. Stereostructure of regioirregular unit of polypropylene obtained with rac-ethylenebis(l-indenyl)zirconium dichloride/methylaluminoxane catalyst system studied by carbon-13-pro ton shift correlation two-dimensional nuclear magnetic resonance spectroscopy. Polymer 1992, 33, 254-258. 

The Pd(MeCN)4(BF4)2-catalysed conversion of allylic alcohols into allylic silanes and boronates has been investigated by product studies, kinetic studies, and H, B, F, and Si NMR (nuclear magnetic resonance) spectroscopy. The two reactions that occur by the same mechanism involve the formation of a palladium allylic alcohol [(a -allyl) palladium] complex after the alcohol is activated by BF3 formed from a BF4 ion of the catalyst. Then, a rate-determining, stereoselective transmetalation with Si(Me)2 and a reductive elimination of the palladium gives the linear silane. B2pin2 replaces Si(Me)2 in the borylation reaction. 

The percent cyclization in polymer [81] was 92-95% as determined by nuclear magnetic resonance spectroscopy. The residual unsaturation was due to the presence of structures [82] and [83]. The formation of structure [83] is favored since Ziegler catalysts polymerize monosubstituted olefins preferentially. A copolymer possessing a higher proportion of [82] was favored on cationic polymerization (BF3/CH2CI2, -70°C). The formation of structure [82] in this instance is due to the similarity of the methylene double bond in the monomer with that in isobutylene. The latter polymerizes readily on cationic initiation. 

Hunger M, Wang W. Characterization of sohd catalysts in the functioning state by nuclear magnetic resonance spectroscopy. Adv Catal 2006 50 149-225. 

An unusual method for the preparation of syndiotactic polybutadiene was reported by The Goodyear Tire Rubber Co. (43) a preformed cobalt-type catalyst prepared under anhydrous conditions was found to polymerize 1,3-butadiene in an emulsion-type recipe to give syndiotactic polybutadienes of various melting points (120—190°C). These polymers were characterized by infrared spectroscopy and nuclear magnetic resonance (44—46). Both the Ube Industries catalyst mentioned previously and the Goodyear catalyst were further modified to control the molecular weight and melting point of syndio-polybutadiene by the addition of various modifiers such as alcohols, nitriles, aldehydes, ketones, ethers, and cyano compounds. 

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