Matrix Reactivity of AlF and AlCl in the Presence of HCl and HBr:  Generation and Characterization of the New Al(III) Hydrides HAlFCl, HAlFBr, and HAlClBr and the Monomeric Mixed Al(III) Halides AlX₂Y (X, Y = F, Cl, or Br)

Abstract

The spontaneous and photolytically induced reactions of AlF and AlCl in the presence of HCl and HBr in solid argon matrices were followed and the products identified and characterized by means of IR spectroscopy. Quantum mechanical calculations allow for a further evaluation of the properties of the reaction products. These are the adducts AlF.HCl, AlF.HBr, and AlCl.HBr, representing the products of spontaneous reactions, and the trivalent Al(III) hydrides HAlFCl, HAlFBr, and HAlClBr, which were formed upon photoactivation of these complexes. All three hydrides are planar molecules (C(s)() symmetry) with bond angles in agreement with the predictions of the VSEPR theory. In addition, the mixed halides AlFCl(2), AlFBr(2), and AlClBr(2) were formed upon photolysis. The bisadducts AlF.(HCl)(2) and AlF.(HBr)(2) are likely to be the precursors to these species.

Theoretical determination of the favorable mechanism of the reaction between AlX and HX (X = Br, Cl, and F)

“…It starts by forming the donor-acceptor complex (AlX(HX) 2 ) which turns into trihalide and molecular hydrogen as recently suggested by Himmel et al [27], the concerted stepwise mechanism (reaction channel (2)): .77 kJ mol -1 when X = Br, Cl, and F, respectively. Indeed, with the large activation barrier energies, this step is expected to be slow.…”

Formation and Stability of the Gaseous Species LiAlCl4, Li2AlCl5 and LiAl2Cl7 – Mass Spectrometric and Quantum Chemical Studies

“…Thermodynamic data (entropy, enthalpy and heat capacity each at 298 K as well as at the reaction temperature) were obtained by employing the FREEH module of the TURBOMOLE program package. With experience from other studies15 the RI‐DFT/BP86 method with the use of extensive basis sets leads to reliable structural, energetic and vibrational data. However, to estimate the accuracy of our method with regard to the type of reactions we explore by mass spectrometry, we determined theoretically the reaction enthalpy of the equilibrium in Equation (1) by both the RI‐DFT/BP86/def‐TZVPP and the MP2/def2‐TZVPP methods.…”

The Aluminyl Anion: A New Generation of Aluminium Nucleophile

“…Binary Al I compounds such as AlH, AlX (X=halide) and Al 2 O have been reported but are only stable for prolonged periods in the gas phase at low pressures [7] . The development of cryochemical methods for the handling of metastable solutions of AlX (X=Cl, Br, I) proved to be instrumental in developing the chemistry of organo‐aluminium(I) systems [7c–f] . Accordingly, the first example of an isolable aluminium(I) complex—tetrameric (AlCp*) 4 1 (Figure 1, Cp*=C 5 Me 5 )—was reported in 1991 by Schnöckel and co‐workers, [8] from the reaction between a metastable solution of AlCl and MgCp* 2 .…”