2018
DOI: 10.1021/acs.jpca.7b11851
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Surprisingly Flexible Oxonium/Borohydride Ion Pair Configurations

Abstract: We investigate the geometry of oxonium/borohydride ion pairs [ether-H-ether][LA-H] with dioxane, THF, and EtO as ethers and B(CF) as the Lewis acid (LA). The question is about possible location of the disolvated proton, [ether-H-ether], with respect to the hydride of the structurally complex [LA-H] anion. Using Born-Oppenheimer molecular dynamics and a comparison of the potential and free energies of the optimized configurations, we show that herein considered ion pairs are much more flexible geometrically tha… Show more

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Cited by 6 publications
(12 citation statements)
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“…40,41 The same applies herein as well, and as an illustration of this in Figure 8, we show representative examples of the optimized structures with the hydrogen-bonded hydronium cation [OH 3 (+) ] at the "back" of [BCF-H (−) ] with respect to the direction defined by the B → H "vector", the calculated [BCF-H (−) ][OH 3 8A,B, respectively. Same as in our two previous studies of the oxonium/ borohydride and the oxocarbenium/borohydride ion pairs, 40,41 in the case considered herein the free-energy difference between the vastly dissimilar face-to-face (Figures 4C and 5A) and the face-to-back (Figure 8) conformers is relatively small on an average for a sum of a few representative optimized structures of each type, that is, within about 2 kcal/mol or less depending on the ether involved. Awareness of a possible mixture of the face-to-face and face-to-back configurations of borohydride intermediates with the solvated proton is important because entropy directly relates to possible structural disorder and the scope of the accessible conformational space.…”
Section: Resultsmentioning
confidence: 99%
“…40,41 The same applies herein as well, and as an illustration of this in Figure 8, we show representative examples of the optimized structures with the hydrogen-bonded hydronium cation [OH 3 (+) ] at the "back" of [BCF-H (−) ] with respect to the direction defined by the B → H "vector", the calculated [BCF-H (−) ][OH 3 8A,B, respectively. Same as in our two previous studies of the oxonium/ borohydride and the oxocarbenium/borohydride ion pairs, 40,41 in the case considered herein the free-energy difference between the vastly dissimilar face-to-face (Figures 4C and 5A) and the face-to-back (Figure 8) conformers is relatively small on an average for a sum of a few representative optimized structures of each type, that is, within about 2 kcal/mol or less depending on the ether involved. Awareness of a possible mixture of the face-to-face and face-to-back configurations of borohydride intermediates with the solvated proton is important because entropy directly relates to possible structural disorder and the scope of the accessible conformational space.…”
Section: Resultsmentioning
confidence: 99%
“…Second, the H 2 activation is predominantly the rate-determining step in hydrogenation reactions, whereas the proton and hydride transfers from the product ion pair, LA–H (−) ··· (+) H–LB ( 1 ), to the substrates generally either have a small barrier or are entirely barrier-less. 19 , 39 , 44 , 45 …”
Section: Introductionmentioning
confidence: 99%
“…Second, the H 2 activation is predominantly the rate-determining step in hydrogenation reactions, whereas the proton and hydride transfers from the product ion pair, LA−H (−) ••• (+) H−LB (1), to the substrates generally either have a small barrier or are entirely barrierless. 19,39,44,45 The paper is organized as follows. First, we present the formation of the initial adduct between the LA and LB and the energetics and structural factors that affect this complexation.…”
Section: Introductionmentioning
confidence: 99%
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“…In the present work, we investigate the reaction of CO 2 + H 2 ⇌ HCOOH, reaction 1 , inside the cavity of a Lewis pair (LP)-functionalized UiO-66 MOF. The recent findings obtained by advanced ab initio molecular dynamics (AIMD) simulations and the possibility of alternative pathways for the hydrogenation of carbonyl compounds suggest that the nature of complex reactions, e.g., FLP-mediated molecular activation, could be challenged in a dynamic picture. This motivated us to investigate reaction 1 using the AIMD methodology, for the first time.…”
Section: Introductionmentioning
confidence: 99%