Chloromethyl cations in cryogenic antimony pentafluoride matrixes and the generation of carbocations from hydrocarbons

Energetics of hydride and electron pair attachment to EX30/+ (E=B, C, Al, Si and X=F, Cl, Br, I) and the study of bonding trends among EX30/+, EX32−/−, and EX3H−/0 by use of ELF and NBO analyses

“…However, taking into account all theoretical data relating to the stabilities of X 3 Al-D systems, the dissociation energies were shown to follow the order F > Cl > Br > I [38]. A G2(MP2) study for X 3 Al-NH 3 gives the same order for the complexation energies (F, À38.6 kcal mol À1 ; Cl, À35.7 kcal mol À1 ; Br, À33.8 kcal mol À1 ), although the differences between energy values are quite small [39]. The calculated donor-acceptor bond energies are strongly dependent on the level of theory and basis set chosen because the basis set of each fragment is extended by the basis functions of the other fragment upon adduct formation.…”

“…While spectroscopic studies of the relative Lewis acidities of boron trihalide donor-acceptor adducts have been extensive [33,34], experimental thermodynamic data are sparse for BX 3 adducts [35][36][37] and nonexistent for CX 3 + analogues. Gas-phase calorimetric measurements of TMAÁBX 3 (TMA = trimethylamine) show that the interaction energy is 3.9 kcal mol À1 lower for BCl 3 than for BF 3 [37] and the heats of reaction for BX 3 (X = F, Cl, Br) with pyridine and nitromethane show that the bond strengths increase in the order BF 3 < BCl 3 < BBr 3 [35]. Photoelectron studies have shown that the donor-acceptor interaction is stronger in the TMAÁBCl 3 and TMAÁBBr 3 adducts than in the BF 3 adduct [36].…”

“…Gas-phase calorimetric measurements of TMAÁBX 3 (TMA = trimethylamine) show that the interaction energy is 3.9 kcal mol À1 lower for BCl 3 than for BF 3 [37] and the heats of reaction for BX 3 (X = F, Cl, Br) with pyridine and nitromethane show that the bond strengths increase in the order BF 3 < BCl 3 < BBr 3 [35]. Photoelectron studies have shown that the donor-acceptor interaction is stronger in the TMAÁBCl 3 and TMAÁBBr 3 adducts than in the BF 3 adduct [36].…”

“…While solid-state structural data for trihalomethyl cations had been previously lacking, electronic structure calculations using various quantum mechanical methods had been used to predict the bonding and chemical properties for www.elsevier.com/locate/fluor Journal of Fluorine Chemistry 125 (2004) 1563-1578 the isoelectronic CX 3 + [1][2][3][4][5][6][7][8][9][10][11][12][13] and BX 3 [1,2,5,[14][15][16][17][18][19]] (X = F, Cl, Br, I) series and related isovalent species such as AH 2 X + and YH 2 X (X = F, Cl, Br, I; A = C, Si, Ge, Sn, Pb; Y = B, Al, Ga, In, Tl) [5]. Results abound for species where X = F [1,2,7,[9][10][11][14][15][16][17][18][19][20][21] or Cl [1,2,6,7,[12][13][14][15][16]…”

Novel superelectrophilic complexes for low-temperature alkane and cycloalkane transformations

“…141 It was also shown that the CC13 + cation readily abstracts a hydride ion from alkanes and cycloalkanes, generating the corresponding carbocations. 141 In order to find the reasons of the superelectrophilic properties of polyhalomethanes in the presence of strong Lewis and protic acids, quantum-chemical calculations were carried out. 142-144 Semiempiricat and nonempirical calculations of CCI4"nAICI 3 (n = 2 or 3) and CBr 4-2AIBr 3 complexes and CX3 +, CHX2 +, CHX 2+, and CX22+ cations (X = (31, Br, 1, but not F) showedt4ZA 43 that, strictly speaking, polyhatomethyl cations, both free and those included in cationic and dicationic complexes CX3+Y -and CX~2+Y2 -(Y = AIBr4 or AI2BrT), are not carbenium ions.…”