Lithium-7 NMR study of the exchange kinetics of the lithium ion with cryptand C221 in methanol solution. Temperature dependence of the exchange mechanism

Kinetic and Mechanistic Aspects of Ethylene and Acrylates Catalytic Copolymerization in Solution and in Emulsion

“…The exchange kinetics of pyridine in either bound or free states has been studied in dichloromethane by both 1 H and 13 C NMR line shape analysis over a wide range of temperatures. 37 At room temperature, a sample of catalyst 2b containing 3% free pyridine exhibits two separate set of resonances for the pyridine protons in 1 H NMR at room temperature (Figure 3a), whereas only a single time-averaged resonance is observed when 10% free pyridine is added (Figure 3b). Using a procedure which has been extensively used for the study of supramolecular processes, the resonance of each time-averaged peak, either in a slow-exchange regime or in fast-exchange regime, can be fitted by a Lorentzian, whose shape is dependent on a parameter τ defined as the lifetime of pyridine interaction (Figure 4).…”

“…Before embarking upon the determination of the rate of the substitution of pyridine by an acrylate (or more generally by an ester), a simpler reaction of pyridine exchange was studied (Scheme ). The exchange kinetics of pyridine in either bound or free states has been studied in dichloromethane by both 1 H and 13 C NMR line shape analysis over a wide range of temperatures . At room temperature, a sample of catalyst 2b containing 3% free pyridine exhibits two separate set of resonances for the pyridine protons in 1 H NMR at room temperature (Figure a), whereas only a single time-averaged resonance is observed when 10% free pyridine is added (Figure b).…”

“…For Scheme , the lifetime τ is given by − 1 normalτ false[ pyridine false] total = k 1 + k 2 1 false[ pyridine false] free Hence, a plot of 1/(τ[pyridine] total ) vs 1/[pyridine] free should yield a straight line of slope k 2 (rate constant of the exchange reaction by a dissociative mechanism) and intercept k 1 (rate constant of the exchange reaction by an associative mechanism).…”

7Li NMR Studies on Complexation Reactions of Lithium Ion with Cryptand C211 in Ionic Liquids: Comparison with Corresponding Reactions in Nonaqueous Solvents

“…Hence, as part of the acquisition of basic data on the reactivities of metal complexes in ILs, we have studied exchange reactions of Li(I) between the Li(I) complexed with cryptand C211 (4,7,13,18-tetraoxa-1,10-diazabicyclo[8.5.5]eicosane) and the uncomplexed Li(I) in DEME-TFSA, EMI-TFSA, MPP-TFSA (MPP = N -methyl- N -propylpyridinium), DEME-PFSA [PFSA = bis(pentafluoroethanesulfonyl)amide], and DEME-HFSA [HFSA = bis(heptafluoropropanesulfonyl)amide] (see Scheme ) using a 7 Li NMR line-broadening method to examine the effect of anionic and cationic components in ILs. Furthermore, although some studies on the complexation reactions of Li(I) with cryptand in nonaqueous solvents have been reported, − we have studied the exchange reactions of Li(I) between the Li(I) complexed with cryptand C211 and the solvated Li(I) in N , N -dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) dissolving LiTFSA to compare with the reaction behavior in ILs.…”

Multinuclear NMR Study of the Solution Structure and Reactivity of Tris(trimethylsilyl)methyllithium and its Iodine Ate Complex

“…The third component present in solutions of 1-Li was assigned the separated ion pair (SIP) structure 1S. We recognize that the observation of distinct NMR signals for CIP/SIP pairs in ethereal solvents is unprecedented, although such structures are wellknown for [2.2.1]crypt 17,18 and HMPA 4f solvated species, where the SIP and CIP have different levels of crypt/HMPA solvation and ligand exchange is slow on the NMR time scale. In such situations the exchange of CIP and SIP carbanions can be much faster than interchange of differently solvated lithium counterions.…”