Equilibrium Gas-Phase Structures of Sodium Fluoride, Bromide, and Iodide Monomers and Dimers

Wann, Derek A.; Rankin, David W. H.; McCaffrey, Philip D.; Martin, Jan M. L.; Mawhorter, Richard

doi:10.1021/jp411202t

Cited by 7 publications

(6 citation statements)

References 64 publications

(172 reference statements)

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“…Although calculations show this process to be rapid, it is also endergonic (see section S6.4B in the Supporting Information), with CF 2 + NaF (monomeric) reverting to NaCF 3 under diffusion control . However, the equilibrium concentration of CF 2 can be increased by coupling the endergonic α-elimination ( K α ) to an exergonic complexation with NaI ( K NaI ) (see Scheme ).…”

Section: Resultsmentioning

confidence: 99%

Difluorocarbene Generation from TMSCF₃: Kinetics and Mechanism of NaI-Mediated and Si-Induced Anionic Chain Reactions

et al. 2020

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The mechanism of CF2-transfer from TMSCF3 (1), mediated by TBAT (2-12 mol%) or by NaI (5-20 mol%), has been investigated by in situ / stopped-flow 19 F NMR spectroscopic analysis of the kinetics of alkene difluorocyclopropanation, and competing TFE / c-C3F6 / homologous perfluoroanion generation, 13 C/ 2 H KIEs, LFERs, CF2-transfer efficiency and selectivity, the effect of inhibitors, and density functional theory (DFT) calculations. The reactions evolve with profoundly different kinetics, undergoing auto-inhibition (TBAT) or stochastic auto-acceleration (NaI), and co-generating perfluoroalkene side products. An overarching mechanism involving direct and indirect fluoride transfer from a CF3-anionoid to TMSCF3 (1) has been elucidated. It allows rationalization of why the NaI-mediated process is more effective for less-reactive alkenes and alkynes, why a large excess of TMSCF3 ( 1) is required in all cases, and why slow-addition protocols can be of benefit. Issues relating to exothermicity, toxicity, and scale-up are also noted.a Relative rates (krel) are for competitive first-order CF2 capture by the alkene/yne, not to overall rates of reaction. b Values in parenthesis by DFT. 26 See sections S3.7, S3.8 and S6.2 in the SI. Singlet CF2 as the ReactiveIntermediate. We began by studying the reaction of TMSCF3 (1) with alkenes 3i, and E/Z-4 and alkyne 5, Table 1. All underwent difluorocyclopropanation, to varying degrees of conversion, in the presence of TMSCF3 (1, 1.5 M) and 1-5 mol % TBAT, or NaI. Reactions of E/Z-4 proceeded stereospecifically, and with >98 % retention. The difluorocyclopropene 8, generated in low yield (12%) from alkyne 5, under the TBATmediated conditions, underwent partial decomposition to unidentified products. In contrast, 8 was quantitatively-generated, and stable, under NaI-mediated conditions, see section S3.3 in the SI. The same difluorocyclopropane products (6, 7) were obtained from 3i and E/Z-4 on thermalization with the zwitterionic CF2-source Ph3PCF2CO2. 22 The relative reactivities (krel) of alkenes 3i, E-4, and Z-4, and the LFER correlation for a-methylstyrenes (3i-vii, r + = -0.6), 23 were independent of the reagent (1 / Ph3PCF2CO2), and initiator (TBAT / NaI), Table 1, 24 within experimental error. Scheme 3. Experimental a and calculated b KIEs for rapid addition of transient singlet CF2 to 3i, at 300 K. 25 a Experimental (exp.) values in THF; and in PhCl, as solvent. 25 b Calculated (calc.) values by DFT, at the M06/6-31+G* level in Gauss-ian09 employing IEF-PCM single points to account for solvation, and goodvibes, kinisot and PyQuiver to compute free energy corrections and KIEs, see sections S1.6 and S6.2 in the SI. 26Kinetic isotope effects for the reaction of p-F-a-methylstyrene 3i with TMSCF3 (1) initiated by TBAT were obtained by a series of competitions of 13 C-and 2 H-labelled a-methylstyrenes 3i against aryl-D4-3i, monitored by 19 F NMR spectroscopy (aryl-DdF = 0.5 ppm). 25 The resulting primary and secondary kinetic isotope effects, Scheme 3, were consistent with thos...

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Section: Resultsmentioning

confidence: 99%

Difluorocarbene Generation from TMSCF₃: Kinetics and Mechanism of NaI-Mediated and Si-Induced Anionic Chain Reactions

et al. 2020

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“…The (NaCl) n clusters, for example,34–63 form polar NaCl bonds across monomeric units in their gas‐phase clusters leading up to the (rock salt) extended solid structure. This general tendency to form polar covalent bonds in clusters in the vapor phases of ionic compounds (clusters foreshadowing the ionic bonding in the solids) is observed for other alkali and group 11 metal halides as well 3–10. Examples of intermediate cases are hard to find, however, be it: 1) clusters held together only by very weak interactions of any sort (be it dipole–dipole or dispersion interactions) growing to form ionic extended solids, or (what would be remarkable indeed), 2) strongly bound clusters condensing to form molecular solids.…”

Section: Introductionmentioning

confidence: 64%

The HgF₂ Ionic Switch: A Triumph of Electrostatics against Relativistic Odds

Donald

Kretz

Omorodion

2015

Chemistry A European J

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A remarkable transition in the chemical bonding in (HgF2)n clusters as a function of n is identified and characterized. HgF2 is a fascinating material. Certain significant consequences of relativistic effects on the structure of the HgF2 molecule, dimer, and trimer disappear in the extended solid. Relativistic effects in Hg ensure that HgX2 molecules (X≡F, Cl, Br, and I) are linear, rigid, and form weakly bound dimers and trimers held together by weak electrostatic and van der Waals-type forces (unlike ZnX2 and CdX2 systems in which the intermonomer contacts are strong polar covalent bonds). For HgF2, the location and nature of an apparent transition from weak interactions in the smallest (HgF2)n clusters to ionic bonding in the (fluorite) HgF2 extended solid has remained a mystery. Computational evidence obtained at the M06-2X, B97D3, and MP2 levels of theory and reported herein indicate that polar covalent bonding in (HgF2)n begins as early as n=5. For n=2 through to n=13, the transition or switch from weak (primarily dipole-dipole-type) intermonomer interactions to a preference for polar covalent bonding occurs within the range 5

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“…Comparison of the structures with different coordinations of atoms showed (Batsanov, 2010) 2007;Groen & Kova ´cs, 2010;Batsanov & Batsanov, 2012;Wann et al, 2014) their values were used along with interatomic distances in crystal structures to establish the above dependencies. These coefficients allow us to calculate the bond lengths in binary compounds of univalent Cu, Ag, Au and Tl for six-coordinate atoms using experimental inter-atomic distances with any CN, and then to determine the Cu + , Ag + , Au + and Tl + radii for this coordination using the anionic radii for CN = 6 (Shannon, 1976).…”

Section: Methodsmentioning

confidence: 99%

Revised radii of the univalent Cu, Ag, Au and Tl cations

Бацанов

2019

Acta Crystallogr B Struct Sci Cryst Eng Mater

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are determined by the additive method from interatomic distances in molecular and/or crystalline halides, oxides, chalcogenides and cyanides with different coordinations of atoms, and then recalculated for the 6-coordination number. The averaged (from 74 structures) values of revised radii are equal to r(Cu + ) = 0.74 Å , r(Ag + ) = 0.99 Å , r(Au + ) = 0.92 Å , r(Tl + ) = 1.22 Å , which are consistent with radii calculated from direct cation-cation contacts in ultimately compressed metals.research papers 40 Stepan S. Batsanov Revised radii of the univalent Cu, Ag, Au and Tl cations

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Equilibrium Gas-Phase Structures of Sodium Fluoride, Bromide, and Iodide Monomers and Dimers

Cited by 7 publications

References 64 publications

Difluorocarbene Generation from TMSCF₃: Kinetics and Mechanism of NaI-Mediated and Si-Induced Anionic Chain Reactions

Difluorocarbene Generation from TMSCF₃: Kinetics and Mechanism of NaI-Mediated and Si-Induced Anionic Chain Reactions

The HgF₂ Ionic Switch: A Triumph of Electrostatics against Relativistic Odds

Revised radii of the univalent Cu, Ag, Au and Tl cations

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Equilibrium Gas-Phase Structures of Sodium Fluoride, Bromide, and Iodide Monomers and Dimers

Cited by 7 publications

References 64 publications

Difluorocarbene Generation from TMSCF3: Kinetics and Mechanism of NaI-Mediated and Si-Induced Anionic Chain Reactions

Difluorocarbene Generation from TMSCF3: Kinetics and Mechanism of NaI-Mediated and Si-Induced Anionic Chain Reactions

The HgF2 Ionic Switch: A Triumph of Electrostatics against Relativistic Odds

Revised radii of the univalent Cu, Ag, Au and Tl cations

Contact Info

Product

Resources

About

Difluorocarbene Generation from TMSCF₃: Kinetics and Mechanism of NaI-Mediated and Si-Induced Anionic Chain Reactions

Difluorocarbene Generation from TMSCF₃: Kinetics and Mechanism of NaI-Mediated and Si-Induced Anionic Chain Reactions

The HgF₂ Ionic Switch: A Triumph of Electrostatics against Relativistic Odds