We have compared the ability of the HF, B3LYP, MP2, G2(MP2), and CBS-QB3 methods to predict the gas-phase complexation enthalpies of eight Lewis bases
Their frustrated pair comprised of the Lewis base
tetramethylpiperidine or TMP and the Lewis acid tris(pentafluorophenyl)borane.
Table 3 lists the computed complexation energies for the [X.sub.3]AlY[C.sub.4][H.sub.4] (X = H, F, Cl and Br; Y = O in furan, Y = NH in pyrrole, and Y = S in thiophen), donor-acceptor complexes and the charge transfer from Y[C.sub.4][H.sub.4] Lewis bases
to Al[X.sub.3] Lewis acids ([Q.sub.t]).
Halogen bonding is directly related to electron donation of lewis bases
to halogen atoms and can be defined as the non- covalent interaction of halogens with halogens or lewis bases
These [CP'M(O)(Eta.sup.2] - O.sub.2)R complexes are air-stable crystalline solids which effect oxygen-atom transfer to Lewis bases
such as phosphines and form 2:1 charge-transfer adducts with TCNE, eg.
Treatment of 5 with a variety of Lewis bases
such as P[Me.sub.3] or pyridine is sufficient to promote loss of [Me.sub.3]SiCl and formation of borabenzene complexes such as 6 (Scheme 2).
The technique uses the Lewis acid tris(pentafluorophenyl) borane and the Lewis base
tetramethylpiperidine that have been modified to be too large to get close enough to form an adduct (Lewis bases
, which carry a lone pair of electrons, can bond with Lewis acids to form molecules called adducts).
Preferred controlling agents for the electrophilic polymerization reaction are organic Lewis bases
such as DMF, DMAc and NMP.