Carbene triel bonds between TrR₃ (Tr = B, Al) and N‐heterocyclic carbenes

Abstract

The carbene triel bond is predicted and characterized by theoretical calculations. The C lone pair of N‐heterocyclic carbenes (NHCs) is allowed to interact with the central triel atom of TrR3 (Tr = B and Al; R = H, F, Cl, and Br). The ensuing bond is very strong, with an interaction energy of nearly 90 kcal/mol. Replacement of the C lone pair by that of either N or Si weakens the binding. The bond is strengthened by electron‐withdrawing substituents on the triel atom, and the reverse occurs with substitution on the NHC. However, these effects do not strictly follow the typical pattern of F > Cl > Br. The TrR3 molecule suffers a good deal of geometric deformation, requiring on the order of 30 kcal/mol, in forming the complex. The R(C···Tr) bond is quite short, for example, 1.6 Å for Tr = B, and shows other indications of at least a partially covalent bond, such as a high electron density at the bond critical point and a good deal of intermolecular charge transfer.

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

“…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.…”

“…Recently, the prevalence of the triel bond has been expanded [61] to encompass carbenes and silylenes as electron donors to TrR 3 . The interaction energies of these complexes were surprisingly large, reaching 90 kcal/mol.…”

The π‐hole tetrel bond betweenX2TOandCO2: Substituent effects and its potential adsorptivity forCO2

“…In recent years, noncovalent interactions (NCIs) have received much attention in many fields, such as crystal engineering, material chemistry, and biology. The type of NIC is gradually extended from hydrogen bonds [ 1–3 ] and halogen bonds [ 4–8 ] to chalcogen bonds, [ 9,10 ] pnicogen bonds, [ 11–13 ] triel bonds, [ 14–16 ] and tetrel bonds. [ 17–21 ] Essentially, these types of interactions can be attributed to the “σ‐hole” interaction, which was first proposed by Politzer and coworkers [ 6 ] in explaining the formation of halogen bonding.…”

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.…”