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Soft Interaction (soft + interaction)

Distribution by Scientific Domains
Chemistry100%

Selected Abstracts

Dispersion-Oriented Soft Interaction in a Frustrated Lewis Pair and the Entropic Encouragement Effect in its Formation

CHEMISTRY - A EUROPEAN JOURNAL, Issue 48 2009
Woo Kim
Abstract The origin of the stability of a frustrated Lewis pair (FLP) tBu3P:B(C6F5)3 is investigated computationally to demonstrate the importance of the dispersion interaction. To this end, the interaction between alkyl-substituted phosphines (Me3P and tBu3P) and hexafluorobenzene (C6F6) is first investigated. Driven by the lone-pair to ,-orbital interaction, the binding energy is found to be even larger than usual ,,, interaction energies between small aromatic compounds. This character, which is inherited to fluorophenyl-substituted B(C6F5)3 in the FLP, induces large flexibility in the FLP over the molecular surface of B(C6F5)3. This soft interaction, in turn, causes an entropic stabilization of the FLP formation in comparison with classical Lewis pairs based on close and tight PB dative bonds. It also suggests a diverse nature of the FLP when it is involved in chemical reactions. Even with the cooperative participation of the perfluorophenyl groups, a detailed inspection of the FLP interaction potential energy surface indicates that the boron atom is still the major interaction site for the pair formation. This non-negligible direct PB interaction, which is related also to the soft nature of the borane frontier orbital, is further supported by substantial spatial overlap between the frontier orbitals on the phosphine/borane fragments and their interaction energy estimations. [source]

Local HSAB principle in the conjugate addition of p -substituted thiophenols to cyclohexenone

INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 1 2005
Rocío Meza
Abstract In the formation of new bonds through the Michel-type addition of thiolates to a ,,,-conjugate system, it is observed that the reaction takes place faster if the thio donor compound contains an electron-rich group or the enone acceptor is highly electron deficient. In contrast, the hard,soft acid,base (HSAB) principle predicts that this reaction is favored when a soft,soft interaction between the reactants takes place. Taking into account that softness is related to a barely electronegative atom of high polarizability, we consider it of interest to analyze the effect of charge transfer of a p -substituent on the softness of sulfur in thiophenols, as well as its impact in the conjugate addition to 2-cyclohexen-1-one. Experiments-in-competition, net charge of X-groups at the p -position of the aromatic ring, the global and local softness at sulfur, and the electrophilicity, obtained by density functional theory (DFT), led to the observation that the reaction is faster for electron attractor thiophenols. The softness at sulfur increases by delocalization of charge through the aromatic ring. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005 [source]

Dispersion-Oriented Soft Interaction in a Frustrated Lewis Pair and the Entropic Encouragement Effect in its Formation

CHEMISTRY - A EUROPEAN JOURNAL, Issue 48 2009
Woo Kim
Abstract The origin of the stability of a frustrated Lewis pair (FLP) tBu3P:B(C6F5)3 is investigated computationally to demonstrate the importance of the dispersion interaction. To this end, the interaction between alkyl-substituted phosphines (Me3P and tBu3P) and hexafluorobenzene (C6F6) is first investigated. Driven by the lone-pair to ,-orbital interaction, the binding energy is found to be even larger than usual ,,, interaction energies between small aromatic compounds. This character, which is inherited to fluorophenyl-substituted B(C6F5)3 in the FLP, induces large flexibility in the FLP over the molecular surface of B(C6F5)3. This soft interaction, in turn, causes an entropic stabilization of the FLP formation in comparison with classical Lewis pairs based on close and tight PB dative bonds. It also suggests a diverse nature of the FLP when it is involved in chemical reactions. Even with the cooperative participation of the perfluorophenyl groups, a detailed inspection of the FLP interaction potential energy surface indicates that the boron atom is still the major interaction site for the pair formation. This non-negligible direct PB interaction, which is related also to the soft nature of the borane frontier orbital, is further supported by substantial spatial overlap between the frontier orbitals on the phosphine/borane fragments and their interaction energy estimations. [source]

Complexes of Bidentate Phosphane Selenide Ligands with Mesitylenetellurenyl Iodide and with Tellurium Diiodide,

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 6 2006
Cristian G. Hrib
Abstract Bis(diphenylphosphanyl)methane diselenide (dppmSe2, 1) and bis(diphenylphosphanyl)ethane diselenide (dppeSe2, 2) reacted with 2 equiv. Br2 or I2 to form the insoluble solid products, dppm(SeX2)2 (X = Br, 3; X = I, 4) and dppe(SeX2)2 (X = Br, 5; X = I, 6). However, using the iodine-like electrophile mesitylenetellurenyl iodide (MesTeI, 7), fairly soluble complexes, dppmSe2[Te(I)Mes]2 (8) and dppeSe2[Te(I)Mes]2 (9), were obtained. Complexes 8 and 9 contain two T-shaped (10-Te-3) Se,Te(Mes),I moieties bridged by dppm or dppe; solid 9 exhibits intermolecular soft,soft interactions between approximately linear Se,Te,I units. In a side reaction accompanying the crystallisation of complex 8, or by the reaction of 1 with Te and I2, a chelate complex dppmSe2TeI2 (10) was formed. Fortuitously, a crystal of the related compound dppeSe2TeI2 (11) was also obtained. In 10, a square planar cis -Se2TeI2 group is part of a six-membered ring, and 11 is a coordination polymer with trans -Se2TeI2 moieties bridged by dppe. Averaged 31P- and 77Se NMR signals including 77Se,31P couplings, together with broad 125Te NMR singlets indicate phosphane selenide ligand exchange in solution, that is, the kinetically labile behaviour of complexes 8 and 9. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]