Structure cristalline du tétraphénylborate de tributylammonium monohydraté: un exemple d'interaction H–π

Aubry, A.; Protas, J.; Moreno-Gonzalez, Edgar; Marraud, Michel

doi:10.1107/s0567740877008930

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“…There has also o or Part been some theoretical work (27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37). In contrast, crystallographic studies, which would provide direct rather than stereochemicallv circumstantial eiidence of such interactions in solids, have been sporadic and often serendipitous, and those involving aromatic .rr systems have been even fewer (38)(39)(40)(41)(42)(43)(44)(45)(46)(47)(48)(49)(50). Moreover, at times a crystal-structure determination actually may have uncovered an X-H ....rr bond, but this feature went unnoticed by the authors because of lack of attention to hydrogen bonding, or was noticed but not reported because the authors may not have been comfortable with the idea of an X-H ...r interaction (see below).…”

Section: [Traduit Par La Rcdaction]mentioning

confidence: 99%

Crystal chemistry of tetraradial species. Part 4. Hydrogen bonding to aromatic π systems: crystal structures of fifteen tetraphenylborates with organic ammonium cations

Bakshi¹,

Linden²,

Vincent³

et al. 1994

Can. J. Chem.

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The aim of this investigation is to provide a classification and examples of N—H …π (and also O—H …π) bonds to the aromatic π systems in organic ammonium tetraphenylborates that would serve as reference for X—H …π(arene) bonds in general. To this end the crystal structures of the tetraphenylborates of the following cations have been determined: Me3NH+, Et3NH+, quinuclidinium, DabcoH+, Et(iso-Pr)2NH+ (monohydrate), (Ph3B)NH[—(CH2)2—]2NHMe+ (Me2CO solvate), Me2NH2+ (MeCN and Et2CO solvates), Et2NH2+, (iso-Pr)2NH2+, azoniacycloheptane, guanidinium (monohydrate), MeNH3+, EtNH3+, and 1-adamantammonium (monohydrate). These structures contain a variety of normal, bifurcated, and trifurcated N—H …π bonds as well as normal O—H …π bonds to the phenyl groups of the anion. The X—H …π bonds will form whenever opportunity arises, even though the result may be unfavourable bonding geometry. Branched bonds and orientational disorder represent compromise solutions in situations where the H(X) hydrogens are presented with competing phenyl acceptors or where the general organization of the crystal structure offers unfavourable bonding conditions to these hydrogens. The distributions of the distances from X or H(X) to the centre of the phenyl-ring skeleton are analyzed in detail, as are also those of the mean X … C and H(X)… C distances to the ring carbons.

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Section: [Traduit Par La Rcdaction]mentioning

confidence: 99%

Crystal chemistry of tetraradial species. Part 4. Hydrogen bonding to aromatic π systems: crystal structures of fifteen tetraphenylborates with organic ammonium cations

Bakshi¹,

Linden²,

Vincent³

et al. 1994

Can. J. Chem.

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“…H 2 0 and presumably also in (n-Pr3NH)-BPh,. H,O (17), whereas in the anhydrous M~, N H + and Et'NH' TBs the N-H group interacts directly with a phenyl ring (1 9, 2 1 ; Knop et a]., to be published).…”

Section: Compound Ementioning

confidence: 99%

“…Detailed examination of the interligand distances (Figs. [17][18][19][20][21] suggests that planarity is maintained in all the iminium ions of Table 7 symmetry for the tri-and of C2 symmetry for the tetrasubstituted ions. This matter remains to be investigated.…”

Section: From Chemistrymentioning

confidence: 99%

“…To substantiate or otherwise the narrowness of the d(C=N) range as well as to obtain a clearer idea of the effect of substitution, we undertook 6-31G* optimization of the equilibrium geometries of substituted iminium ions (Tables 7, 8, and G). Aiming at maximum economy of the computational effort we chose F and C1 as the monatomic substituents with the most substantial electron-withdrawing 9 N + -H., ,=-( 15, 18-2 1); N+-H., ,o,-H,, .=- ( 17); powers, and Li and Na as substituents acting in the opposite 0-H.. .T (22, 3 1, 32 TT conjugation. This choice of substituents was furthermore intended to make unnecessary an investigation of the effect of individual composite substituents (e.g., CH,, NH2), which would have added significantly to the already extensive projected computer requirements. '…”

Section: T -Interaction By Implication It Is Reasonable Tomentioning

confidence: 99%

“…1680 cm-' (Table 2).' From the crystal structures of A-E and those of other tetraphenylborates (15)(16)(17)(18)(19)(20)(21)(22) we have been able to elucidate some of the principles of ion packing in tetraphenylborates of small cations, and also to provide evidence for the existence of hydrogen bonding between cation or H,O hydrogens and the aromatic .rr system of the phenyl ring(s). In addition, a b irzitio (6-3 1G:" calculations on a variety of substituted [LL'c=NL"L"') ' cations have made it possible to examine the effects of substitution on the geometry and the net charges in such cations, as well as the existence of a correlation between the C=N bond length and the electron density p(r,) at the bond critical point (cf.…”

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Crystal chemistry of tetraradial species. Part 3. Salts of aliphatic Schiff bases crystallizable from aqueous media: crystal structures of five iminium tetraphenylborates and a 6-31G* ab initio study of simple iminium ions

Knop¹,

Cameron²,

Bakshi³

et al. 1993

Can. J. Chem.

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. Recrystallization of a primary or secondary alkylammonium tetraphenylborate (TB) from approximately 1 : 1 mixtures of Me2C0 (or MeEtCO) and water yields, against expectation, the TB of the corresponding iminium cation and thus provides an easy route to a variety of aliphatic Schiff bases. The crystal structures of five such salts have been de- are discussed in detail, as also is the tendency of the small iminium ions to orientational disorder. The range of the C=N bond length in these and other iminium salts is quite narrow, with 1.283(12) A as the mean (uncorrected) value. Where a hydrogen atom(s) is attached to the iminium nitrogen, it will form a hydrogen bond (simple or bifurcated) with the aromatic n system of the nearest phenyl ring(s). The narrowness of the C=N bond-length range with respect to substitution on the cation has prompted a detailed 6-31G" ab ir~itio study of the effect, on the geometry of the [H,c=NH,]+ ion, of a partial or complete replacement of the H atoms by one of the following substituents: F, C1, CN, Li, and Na. The 46 structures optimized in planar geometry were supplemented by a number of optimizations of similarly substituted ethylenes as well as by a few optimizations in perpendicular geometry. Analysis of the numerical results involves the bond lengths and angles, Mulliken EM and (in part) Lijwdin EL net charges on the atoms, and electron densities p, = p(r,) at the bond critical points. Only a limited use has been made of comparisons involving the total electronic energies E (substitutional isomerism). Since the above substituents span the entire electronegativity scale, and CN provides for the possibility of conjugation, the effects they produce are expected to bracket the effects that would be produced by any other substituents. The calculations confirm the essential narrowness of the C=N bond-length range in iminium ions. They also show that, at least in the 6-31G:!: scheme, the nitrogen in [H'C=NH,]+ carries a significant negative net charge (both in terms of EM and e,), which is contrary to the conventional representation of the ion as H2C=N+H2. The trends observed in the parameters are smooth and highly self-consistent except for the tri-and tetrasubstituted ions containing Li or Na, where interligand repulsions may invalidate the assumption of planarity. Many of the parameters can be represented to a high degree of correlation as linear functions a, + actzc(X) + aNtl,(X) of the numbers tz of substituent atoms X on the C and N atoms. This representation makes it possible to estimate the contribution to the parameter value from the substitution at the distant atom of the C=N bond, i.e., the extent of localization of the effect produced by the substituent. The success of the linearization of the parameter variation raises the important question of whether the apparent additivity is genuine and intrinsic or merely a property of the 6-31G:': optimization scheme. In other words, will additivity be retained, functionally, for sets of parameters obtained from higher level ab ini...

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Aspects of the Stereochemistry of Four‐Coordination and Five‐Coordination

Favas

Kepert

1980

Progress in Inorganic Chemistry

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Structure cristalline du tétraphénylborate de tributylammonium monohydraté: un exemple d'interaction H–π

Cited by 20 publications

References 1 publication

Crystal chemistry of tetraradial species. Part 4. Hydrogen bonding to aromatic π systems: crystal structures of fifteen tetraphenylborates with organic ammonium cations

Crystal chemistry of tetraradial species. Part 4. Hydrogen bonding to aromatic π systems: crystal structures of fifteen tetraphenylborates with organic ammonium cations

Crystal chemistry of tetraradial species. Part 3. Salts of aliphatic Schiff bases crystallizable from aqueous media: crystal structures of five iminium tetraphenylborates and a 6-31G* ab initio study of simple iminium ions

Aspects of the Stereochemistry of Four‐Coordination and Five‐Coordination

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