On the existence of trivalent stannyl cations in solution

Arshadi, Mehrdad; Johnels, Dan; Edlund, Ulf

doi:10.1039/cc9960001279

Cited by 23 publications

(26 citation statements)

References 11 publications

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“…[66] www.eurjic.orgnBu 3 SnOTf (4) and 6 with H 2 : No reaction was apparent by 119 Sn NMR spectroscopy at ambient temperature after 2 h or at 50°C after a further 18 h. Only unreacted 4 was observed in solution ( 119 Sn NMR: δ = 151 ppm). [70] B(C 6 F 5 ) 3 (1) and 5 with H 2 : No reaction was apparent by 11 B NMR spectroscopy at ambient temperature after 2 h with only 1 ( 11 B NMR: δ = 58.6 ppm) being observed in solution. [61] The mixture was then heated to 50°C for a further 18 h, after which analysis by 11 B NMR spectroscopy exhibited two signals: a minor peak corresponding to an unknown product (δ = 3.5 ppm) and a major peak arising from [HB(C 6 F 5 ) 3 ]…”

Section: And 26-di-tert-butylpyridine (5) With Hmentioning

confidence: 95%

“…Removal of all volatiles from the filtrate afforded a colourless oil, which was also analysed by multinuclear NMR spectroscopy. The absence of resonances at δ = -40.0, 1.7 and 172 ppm in the 11 B, 31 P and 119 Sn NMR spectra, respectively, indicated complete consumption of both 4 [70] and 23. [71] However, there were no signals in the former two spectra that could be assigned to any of the expected dehydrogenation products, [36] Further evidence for the occurrence of a reaction other than dehydrogenation was apparent from the observation of phosphorus-tin coupling (J P-Sn = 196 Hz) in both the 31 P and 119 Sn NMR spectra.…”

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confidence: 95%

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Reactions of Amine– and Phosphane–Borane Adducts with Frustrated Lewis Pair Combinations of Group 14 Triflates and Sterically Hindered Nitrogen Bases

et al. 2010

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The ability of trialkyl Group 14 triflates in combination with amine and pyridine bases to dehydrogenate amine– and phosphane–borane adducts has been investigated. By using multinuclear NMR spectroscopy, it has been shown that Me2NH·BH3 (11) is efficiently converted to [Me2N–BH2]2 (12) by the so‐called “frustrated Lewis pair” (FLP) of nBu3SnOTf (4, –OTf = –OSO2CF3) and 2,2,6,6‐tetramethylpiperidine (6). Within the scope of the study, exchange of the Lewis acid effects the rate of dehydrogenation in the order: 4 > Me3SiOTf (2) > Et3SiOTf (3). Exchange of the Lewis base for 2,6‐di‐tert‐butylpyridine (5) has also been shown to reduce the rate of reaction, whereas 1,3‐di‐tert‐butylimidazol‐2‐ylidene (7) reacted directly with 2 to afford 1,3‐bis‐tert‐butyl‐4‐(trimethylsilyl)imidazolium triflate (8[OTf]). For FLP combinations for which dehydrogenation reaction times are longer, detectable quantities of [H2B(μ‐H)(μ‐NMe2)BH2] (14) are observed. Both the dehydrogenation reaction and competitive formation of this product are proposed to proceed by initial hydride abstraction by the Lewis acid, followed by deprotonation by the Lewis base, or combination with further dimethylamine–borane and elimination of [Me2NH2]OTf (18[OTf]), respectively. In contrast to 11, MeNH2·BH3 (22) was not found to cleanly dehydrogenate to either [MeNH–BH2]3 or [MeN–BH]3 under the same conditions. An alternative reaction pathway was observed with either 2 or 4 and 6 with Ph2PH·BH3 (23), resulting in P‐silylation or P‐stannylation of the phosphane–borane, respectively.

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Section: And 26-di-tert-butylpyridine (5) With Hmentioning

confidence: 95%

mentioning

confidence: 95%

Reactions of Amine– and Phosphane–Borane Adducts with Frustrated Lewis Pair Combinations of Group 14 Triflates and Sterically Hindered Nitrogen Bases

et al. 2010

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“…29,61 Kira et al also prepared the n-Bu 3 Sn + derivative as its TFPB − salt, using the traditional hydride transfer method (Section 1.2.2, Scheme 1.2, C) and reported the low-field resonance of the cationic Sn atom to be 356 ppm. 7 This conclusion was, however, later questioned by Edlund et al, 41 who pointed out that the values of 360 60 and 356 7 ppm assigned to the cationic Sn atom are better attributed to the covalently bound arene complexes, quite similar to the case discussed above of the silylium ions vs Wheland σ -complexes problem. On the basis of an empirical correlation between the 29 Si and 119 Sn NMR chemical shifts, the resonance of the truly free trigonal-planar Me 3 Sn + cation was expected to be observed at a much lower field of 1500-2000 ppm, a conclusion that also gained support from theoretical calculations.…”

Section: Scheme 110mentioning

confidence: 96%

Heavy Analogs of Carbenium Ions: Si‐, Ge‐, Sn‐ and Pb‐Centered Cations

Lee

Sekiguchi

2010

Organometallic Compounds of Low‐Coordinate Si, Ge, Sn and Pb

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This so-called 'hydride-transfer reaction' is the most commonly used and straightforward method for the generation of stable RR R E + cations. The driving force of this process, involving oxidation of the starting hydride RR R EH with a powerful Lewis acid (typically, trityluim ion Ph 3 C + ), is the relative strength of the breaking and forming bonds: stronger C-H vs weaker E-H. A variety of heavy analogs of carbenium ions, intra-or intermolecularly stabilized by coordination to n/π -donors, counteranions or nucleophilic solvents, can be readily prepared by this route (Scheme 1.2). 5 -7 As a drawback of this synthetic approach one should mention the steric bulkiness of the Ph 3 C + reagent, which may hamper its interaction with hydrides RR R EH bearing voluminous substituents necessary for the kinetic stabilization of the resulting cation.

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“…They concluded that the naked cations do not exist in solution and what were previously observed were, in fact, donor-acceptor complexes with solvent molecules. 8 In 1996, Arshadi et al 1 employed "'Sn/^Si NMR shift correlations to argue also that no naked triorganostannyl cations had been observed in solution to date.…”

Section: Introduction Triorpanostannyl Cationsmentioning

confidence: 98%

Electrospray Mass Spectrometric Studies on the Solution Chemistry of Triorganostannyl Trifluoromethanesulfonates

Dakternieks

Lim

1999

Phosphorus, Sulfur, and Silicon and the Related Elements

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Compounds of the type R 3 Sn(OSO2CF 3 ) (triorganostannyl trifluoromethanesulfonates, R = Me, Bu, Ph) were synthesized and investigated in solution using electrospray mass spectrometry. The mono-acetonitrile adduct [R 3 Sn»(CH 3 CN)] + is the dominant ionic species in acetonitrile solution, with a weaker signal owing to R 3 Sn + . The relative intensity of R 3 Sn + increases significantly upon the use of dichloromethane as a solvent. Variable temperature " 9 Sn NMR studies were also undertaken on the trimethylstannyl and triphenylstannyl trifluoromethanesulfonates in dichloromethane solution. The Sn chemical shifts and Lewis-base adduction studies reveal that the triorganostannyl trifluoromethanesulfonates are only slightly more Lewis-acidic than the corresponding triorganostannyl chlorides. These solutions are too labile to be studied on the NMR timescale.

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On the existence of trivalent stannyl cations in solution

Abstract: It is shown by NMR spectroscopy that no free trigonal stannyl cations in solution have been observed to date as also expected from theoretical ab initio IGLO calculations.

Cited by 23 publications

References 11 publications

Reactions of Amine– and Phosphane–Borane Adducts with Frustrated Lewis Pair Combinations of Group 14 Triflates and Sterically Hindered Nitrogen Bases

Reactions of Amine– and Phosphane–Borane Adducts with Frustrated Lewis Pair Combinations of Group 14 Triflates and Sterically Hindered Nitrogen Bases

Heavy Analogs of Carbenium Ions: Si‐, Ge‐, Sn‐ and Pb‐Centered Cations

Electrospray Mass Spectrometric Studies on the Solution Chemistry of Triorganostannyl Trifluoromethanesulfonates

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