Triel‐Bonded Complexes between TrR₃ (Tr=B, Al, Ga; R=H, F, Cl, Br, CH₃) and Pyrazine

Abstract

Complexes between TrR (Tr=B, Al, Ga; R=H, F, Cl, Br, CH ) molecules and pyrazine have been characterized at the MP2 and CCSD(T) levels of theory. The adducts can be grouped according to the type of molecular arrangement. The first situation places the Tr atom in the plane of the pyrazine ring and contains a triel bond to the N lone pair. For the boron complexes the orbital interaction energy is almost equal to the electrostatic component, while the former is only half the latter for Tr=Al and Ga. The two monomers are stacked above one another in the second configuration, which depends to a greater degree upon orbital interaction and dispersion. The former complexes are more strongly bonded than the latter. Interaction energies (E ) for the stronger complexes vary between -50 and -20 kcal/mol for BBr and Ga(CH ) paired respectively with pyrazine. E is much smaller for the stacked configurations, ranging from -8 for GaF to -1.4 kcal/mol for BF . The value of the maximum of the electrostatic potential correlates poorly with E , attributed in part to monomer distortions upon complexation.

Influence of N-Base and O-Base Hybridization on Triel Bonds

“…TrR 3 in the TrB complex undergoes distortion from the planar structure to an umbrella one, which is consistent with the conclusion in the previous study. 14 …”

“…Besides, TrB has relatively large polarization energy, accompanied with prominent distortion of the triel donor molecule. 14 …”

Competition between Intra and Intermolecular Triel Bonds. Complexes between Naphthalene Derivatives and Neutral or Anionic Lewis Bases

“…The findings presented above can be placed in the context of several earlier sets of calculations. For example, an earlier study [87] Our own earlier study of a triel bond pairing TrR 3 with pyrazine [73] applied the same level of theory as here, but involved a different base. In order to facilitate some comparison, it could be considered that the GaH 3 molecule has a π-hole very similar in magnitude to that of C 10 H 7 GaF 2 .…”

“…There are also exceptional cases wherein a tetravalent Tr atom can generate a σ-hole [57]. This TrB has generated sufficient interest so as to be the focus of a number of prior quantum chemical studies [58][59][60][61][62][63][64][65][66][67][68][69][70][71][72][73]. Our own earlier study of the TrB [73] in complexes of TrR 3 (Tr = B, Al, Ga; R = H, F, Cl, Br, CH 3 ) with pyrazine provides some information about the influence of various substituents on the energy, geometry, and properties of this interaction.…”

Chalcogen bonding of two ligands to hypervalent YF4(Y = S, Se, Te, Po)

“…26 This Coulombic attraction is supplemented by orbital interactions such as charge transfer and dispersion terms which are also important components. 44 The positive area is not limited to a σ-hole, but can in certain cases occur above a planar molecule, as in triel bonded systems, 45,46 where it is commonly referred to as a π-hole. 47,48 Various aspects of chalcogen bonds have been discussed in recent years.…”